                                                                   
                     =====================================
                           T3 Dragon / CoCo Emulator
                                  Version 0.8
                      Copyright 1995-1997 by Paul Burgin
                     =====================================
  
  1    Introduction
  
  Welcome to T3. T3 is a multi-tasking Dragon and Tandy CoCo II emulator for
  80386 PCs and compatibles. Used in conjunction with a ROM file from one of
  these  6809 based home computers, it enables you to run your old  software
  on a modern PC.
  
  Note  that  a  ROM file is not included in the emulator distribution.  You
  must  obtain  one from elsewhere before you can use T3 (see end  of  these
  notes for a World Wide Web pointer to the ROM files).
  
  2    What Is Emulated
  
  The following components are emulated by T3:
      6809 CPU;
      Automatically emulates Dragon 32, Dragon 64 or Tandy CoCo II
       compatible architecture as appropriate to the ROM file provided;
      All machines are provided with 64K of RAM, a switchable 16K BASIC
       ROM, and a 16K ROM cartridge area;
      SAM chip with low/high/mid-resolution graphics, realistic text and
       semi-graphics;
      Bi-directional cassette interface;
      6-bit and 1-bit audio output;
      Digital joysticks;
      Interrupt driven counter/timer mechanism (not 100% accurate).
  
  T3 also has additional features such as:
      Multiple sessions within a single instance of T3;
      Pre-emptive multitasking;
      Snapshot and image facilities;
      Variable speed control;
      Audio mute and volume control.
  
  The following are not emulated by this version of T3 (some of the items in
  this list may be implemented at a later date, and others won't):
      Disk drives;
      Serial port / parallel port;
      Analogue joysticks;
      Joysticks via the PC mouse or joystick.
  
  3    System Requirements
  
  The minimum system specification is shown below. T3 will not start if your
  system does not meet these requirements:
      80386 processor;
      MS-DOS v4.00;
      VGA graphics adapter;
      199K of base memory (approx.).
  
  The following is the recommended system specification for running a single
  session with full speed and functionality:
      80386 DX-25 or above;
      MS-DOS v7.00 (Windows 95) or above;
      VGA or SVGA graphics adapter;
      SoundBlaster v1.0 or above;
      199K of base memory (approx.).
  
  If  you have additional base memory available then you will be able use T3
  to  run  more  than one Dragon/CoCo session (task) at once.  Approximately
  133K  of  base memory is required for each additional task (subject  to  a
  maximum of four tasks).
  
  If  you have additional processing power available then you can choose  to
  have  T3  execute  all of your tasks simultaneously. Tasks  then  continue
  running even when switched into the background. When T3 is used for multi-
  tasking smoother emulation should be obtained for faster CPUs.
  
  4    What Does T3 Mean?
  
  Well,  it's  nothing to do with that pop group, of that you can  be  sure!
  There  is  also now a magazine called T3, but again this emulator  has  no
  connection with that magazine.
  
  Although it still hasn't reached v1.00 and a wider distribution, T3 has in
  fact been around for nearly two years. The name T3 was originally intended
  to be only a working title, being an extreme contraction of "PC-Dragon III
  (386  Turbo  Edition)". This name was conceived at  a  time  when  T3  was
  expected  to re-use code from my previous emulator PC-Dragon II.  However,
  it  turned out that code re-use was not practical and as a result  T3  has
  been written from scratch as a new emulator in it's own right.
  
  Nevertheless, the name has now become familiar and so it would be somewhat
  confusing to change it at this stage. It will therefore remain as T3 until
  such  a  time  as  I  can  think of something  better!  If  you  have  any
  suggestions then please let me know!
  
  5    Files In The T3 ZIP File
  
  The following files are supplied in the ZIP file:
  
  WHATSNEW.008        Summary of changes for this release.
  README.TXT          Instructions (this file).
  T3.EXE              T3 executable.
  T3.DAT              T3 title page (can be deleted to save space).
  
  6    Getting Started
  
  To  begin  using the emulator you need to copy a ROM file  into  the  same
  directory as T3.EXE. Having done so type "T3" to start the emulator.
  
  T3  tries a variety of different names when it searches for a ROM file and
  will  use  the first file that it finds. Valid names include  T3,  DRAGON,
  DRAGROM,  COCO,  TANDYROM, and D64ROM1. You can use files  either  in  PC-
  Dragon  II's  DGN format or in Jeff Vavasour's ROM format; T3 auto-detects
  which format you are using irrespective of the file name.
  
  If  you  have several ROM files and want to use a particular one then  you
  can do this by specifying the -r option on the command line when you start
  T3. E.g.
  
                                T3  -rCOCO.ROM
  
  Note  that  if  the ROM file name includes a space then you will  need  to
  enclose the entire option in double quotes. E.g.
  
                            T3 "-rD32 AND ALLDREAM"
  
  If  you are using T3 to emulate a Dragon 64 and want to use the 64K  BASIC
  mode  then you will additionally need the 64K BASIC ROM. This must  be  in
  DGN format and have file name D64ROM2.DGN.
  
  Once started press any key to proceed from the title page and T3 will boot
  your Dragon or CoCo. When you wish to quit the emulator press F12 followed
  by END and then RETURN.
  
  7    Emulator Controls
  
  The  following  are  key combinations which can be  used  to  control  the
  emulator:
  
  F1                  Display emulator version.
  F2                  Load image (hold SHIFT to save image).
  F3                  Load snapshot (hold SHIFT to save snapshot).
  F4                  Cassette mode control.
  F5                  Jump to Alldream.
  F6                  Jump to Dreambug.
  F9                  Previous task.
  F10                 Next task.
  F11                 Create new task.
  F12                 Delete current task (hold SHIFT to auto-save image).
  
  Alt-A               Artifacting control.
  Alt-C               Cursor keys control.
  Alt-F               Audio resampling frequency control.
  Alt-L               Lower case text toggle.
  Alt-P               Suspend task (i.e. pause).
  Alt-Q               Audio on/off control.
  Alt-R               Resume task.
  Alt-S               Speed control.
  Alt-T               Text colour control.
  Alt-V               Audio volume control.
  Alt-X               Task type control.
  
  SCROLL LOCK         Freeze task.
  Ctrl-Alt-Delete     Warm reset (hold SHIFT for cold reset).
  
  Additionally, PGUP has the same function as F9, PGDN has the same function
  as  F10,  INSERT  has  the same function as F11 and DELETE  has  the  same
  function as F12.
  
  F8 has the same function as Ctrl-Alt-Delete. It is not needed when running
  T3  in MS-DOS, but should be used when running T3 in environments where it
  is  not  safe to press Ctrl-Alt-Delete (e.g. when running T3 in a DOS  box
  under MS-Windows).
  
  The  NUM  LOCK key can be used instead of the Alt keys in order to prevent
  joystick fire button being pressed.
  
  The following keys can be used in file name input dialogue boxes:
  
  F4                  Paste Dragon/CoCo name.
  DELETE              Backspace.
  HOME                Erase all.
  ESC                 Quit.
  RETURN              Accept.
  
  Additionally Ctrl-Alt-Delete, F8 and F12 have the same function as ESC.
  
  The following keys can be used in selection boxes:
  
  LEFT                Previous option.
  RIGHT               Next option.
  UP                  First option.
  DOWN                Last option.
  ESC                 Quit.
  RETURN              Accept.
  
  Additionally  HOME has the same function as UP. END has the same  function
  as DOWN. Ctrl-Alt-Delete, F8 and F12 have the same function as ESC.
  
  8    Video
  
  T3  fully emulates the default Dragon/CoCo text mode and all semi-graphics
  modes.  It is also possible to select either realistic or idealistic  text
  mode  colours by pressing Alt-T. With true text colours "ON"  the  colours
  will  be either dark green on green or dark red on light orange. With true
  text colours "OFF" the colours match with low-resolution graphics and will
  be  either  black on green or black on orange (this improves the  look  of
  games like Copta Snatch and Tetras).
  
  High/mid-resolution graphics modes are available in 2-colour  or  4-colour
  palettes,  as provided by the Dragon/CoCo. All 2-colour black/white  modes
  are also available in artifacted colours by pressing Alt-A and selecting a
  "RED" artifacted palette or a "BLUE" artifacted palette.
  
  All  28 "regular" high/mid-resolution graphics modes are supported by  T3.
  In  this context "regular" means modes where the number of bytes displayed
  for  each scan line is equal to the video memory increment for each  line.
  Other modes where video memory is skipped or repeated will be displayed as
  the nearest equivalent regular mode instead.
  
  As  there  is  no  worthwhile reason to implement the irregular  modes  (I
  haven't found any commercial software which uses them), it's very unlikely
  that they shall ever be implemented by T3 (note however that PC-Dragon  II
  does implement all of them).
  
  T3  implements an additional 4 mid-resolution graphics modes with 16 lines
  of 16 bytes (total 256 bytes) which do not exist on the CoCo/Dragon! Refer
  to  the  virtual  cassette  MODES.CAS supplied  with  PCDGN201.ZIP  for  a
  demonstration of all of the high/mid-resolution graphics mode classes.
  
  9    Audio
  
  T3  provides emulation of Dragon/CoCo audio by using a SoundBlaster  card,
  if installed. There is no option to hear audio via the PC beeper.
  
  In  order  to  receive audio you must ensure that your BLASTER environment
  variable is set correctly when you start T3. This should contain a  string
  such  as "A220" to specify the base IO address of your SoundBlaster.  When
  running  under  Windows  95,  the string will  normally  be  set  for  you
  automatically,  but  under  MS-DOS you  will  need  to  set  the  variable
  yourself.  Typically this involves adding a command such as the  following
  to  your  AUTOEXEC.BAT (but the settings must reflect the actual  hardware
  settings of your card):
  
                            SET BLASTER=A220 I5 D1
  
  Unfortunately SoundBlaster cards provide a very slow response to software.
  Because  of this, T3 cannot afford to wait for the SoundBlaster to respond
  to  audio output on demand. Instead, T3 resamples all audio output at run-
  time.
  
  By  default  T3  uses  a  resampling frequency of  16KHz,  which  provides
  satisfactory results for most games. However, you may wish to  change  the
  frequency  when  the default is not ideal for the software  that  you  are
  using.  To  do  this,  press Alt-F and select a new  resampling  frequency
  between 4KHz and 40KHz. Software which uses 1-bit sound rather than  6-bit
  sound  typically  requires  higher  resampling  frequencies  (e.g.  Planet
  Invasion, Intergalactic Force).
  
  Note  that the resampling frequency is relative to the task target  speed,
  thus  if  you  increase  the target speed of a task  then  the  resampling
  frequency  is  also proportionately increased. Dramatically  increasing  a
  task   target  speed  without  reducing  the  resampling  frequency   will
  eventually cause a minor reduction in the emulator's efficiency.
  
  Audio output can be toggled on and off by pressing Alt-Q. The volume level
  may be adjusted by pressing Alt-V.
  
  10   Music
  
  The  default  audio  settings are satisfactory  for  most  sound  effects.
  However,  if  you intend to use T3 to play music (or other sounds  lasting
  longer  than  a quarter of a second at 100% speed) then you will  need  to
  take  note  of the following recommendations for improving the quality  of
  the music reproduction (in decreasing order of importance):
  
  1.   Audio  output  will be fragmented if a task is being timesliced  with
       other tasks. For best results set the task type to "EXCLUSIVE".
  
  2.   Although  the  dynamic speed adjustments made by T3 are  not  usually
       noticeable, when playing music they become very obvious as changes in
       the  pitch  of  notes.  It is therefore highly recommended  that  the
       dynamic target speed be set to "OFF" when playing music. To do  this,
       allow  the music to play for awhile and then press Alt-S followed  by
       HOME and RETURN. See also the notes in the Target Speed section.
  
  3.   Depending on the software in use, increasing the resampling frequency
       may  provide noticeable improvements to the audio quality. To do this
       press Alt-F (see previous section).
  
  4.   Quitting  MS-Windows environments and running T3 in pure  MS-DOS  can
       provide minor improvements to the audio quality.
  
  11   Joysticks
  
  Joysticks are emulated using the PC cursor keys (but can be disabled using
  Alt-C).  Both of the left and right joysticks are operated simultaneously,
  but the fire buttons may be operated separately.
  
  Press  the  left Ctrl key or right Alt key to simulate the  left  joystick
  fire  button.  Press the left Alt key or right Ctrl key  to  simulate  the
  right  joystick fire button. Pressing the keypad 5 key will simulate  both
  fire buttons at once.
  
  The  joystick emulation is digital rather than analogue and therefore will
  not work with all games.
  
  12   Virtual Cassettes
  
  When the Dragon/CoCo requires access to cassettes you will be prompted for
  the name of an MS-DOS file to be used as a virtual cassette.
  
  Type the name in the box with or without a CAS extension and press RETURN.
  Pressing F4 pastes the name of the file that the Dragon/CoCo is attempting
  to  access (if any) into the box, but you can only enter well formed names
  so some characters may be translated to underscores.
  
  If you are running T3 with MS-DOS v7.00 or above and IFSHLP loaded (i.e. a
  DOS  box  in Windows 95) then you can type up to 250 characters  including
  upper  case  letters, lower case letters, numbers, special characters  and
  spaces. If running T3 with an earlier version of MS-DOS or without  IFSHLP
  loaded  (i.e.  MS-DOS  mode in Windows 95) then  you  can  enter  only  75
  characters  which  may  include upper case letters,  numbers  and  special
  characters.  If  long file names are available then the  cursor  is  blue,
  otherwise it is grey.
  
  When  saving a cassette, should you enter the name of a file which already
  exists  then  T3 will display the message "FILE EXISTS" and allow  you  to
  choose  to  cancel the file name, append to the existing file, or  replace
  it.
  
  T3  does  not  impose a limit on the length of cassette  files.  They  are
  normally closed when the file mode changes or if you reset or quit a task,
  but  can also be closed manually by pressing F4 and selecting CLOSED.  You
  will need to do this to write separate programs consecutively to different
  MS-DOS files, to recover from an ?IO ERROR, or to enter a file name  after
  pressing Quit.
  
  Unlike  all  other  emulation performed by T3, the cassette  emulation  is
  implemented  at the operating system level rather than the hardware  level
  (ROM  breakpoints are installed at start-up). Cassette emulation therefore
  does  not  work for the (very small number of) programs which  access  the
  cassette mechanism at the hardware level.
  
  If  running multiple timesliced tasks then background tasks are  permitted
  to   momentarily  interrupt  foreground  tasks  in  order  to  prompt  for
  filenames.
  
  13   Cartridges
  
  There are two ways to load a cartridge into T3. Firstly, if you would like
  the cartridge to be loaded at boot-up time then you must append it to your
  ROM file. To do this type an MS-DOS command such as the following:
  
                COPY  /B  DRAGON.DGN  +  CART.RAW  DRAGCART.DGN
                                T3  -rDRAGCART
  
  Note that your cartridge must be in a raw (pure data only) format.
  
  The  second  method of loading a cartridge into T3 is to  use  a  snapshot
  file.  This is usually the best way to load cartridge games into  T3.  See
  later section on snapshot files for more details.
  
  Whichever  method  of  loading a cartridge is used,  it  may  or  may  not
  automatically execute, depending on how it was designed.
  
  If  you  load the Alldream cartridge into the emulator then the F5 and  F6
  keys  can  be used to immediately jump to Alldream (F5) or Dreambug  (F6).
  The  exact  function performed by F5 is: push PC register onto the  stack,
  push the value of ($FFFE) onto the stack, push $C000 onto the stack, clear
  the  I flag in the condition code register, and finally execute a jump  to
  $A93A.  This  has the effect of returning to text mode and then  executing
  Alldream.  When  you quit Alldream a reset occurs. F6  performs  the  same
  function except that $D384 is pushed onto the stack rather than $C000.
  
  Remember  that  in order for Alldream/Dreambug to function correctly,  the
  CLEAR  command  should be used to set-up their workspace before  they  are
  executed. A warning will appear if you do not do this.
  
  14   Images
  
  Images are copies of the entire workspace of a T3 task. Image support  was
  initially  implemented in order to aid debugging of the emulator  but  has
  now  been made available for general use. The use of images allows you  to
  save the context of a task to continue at a later date, or perhaps save  a
  position in a game for instant replay.
  
  To  save  an  image  simply press SHIFT + F2. The  current  task  is  then
  immediately saved to disk. It can be reloaded at any time by pressing  F2.
  All  task  settings and ROMs are saved in the image, so that the  reloaded
  task state is identical to the saved state.
  
  Note that T3 provides access to just one image file at a time. It does not
  prompt for a file name when you load or save an image. However you can use
  the -i command line option to change the image file name when you start T3
  (see notes on -r option for applicable syntax).
  
  Note  also  that  images should not be considered to be snapshots  because
  they  are  much  larger  than snapshots need to be, and  are  non-portable
  between  emulators (or even between different versions  of  T3).  Use  the
  snapshot facility instead if you need to make files portable.
  
  15   Automatic Images
  
  T3  can also create "automatic" images which are used slightly differently
  to  standard images. To save an automatic image hold down SHIFT  when  you
  delete a standard task and you will be given the option of auto-saving it.
  After  doing  so,  when  you  next start  T3  the  image  will  be  loaded
  automatically, creating an "automatic" task.
  
  Automatic  tasks behave slightly differently to standard tasks;  they  are
  automatically  saved  when deleted. Also, some T3  messages  are  slightly
  different,  and to protect the integrity of the task and the copyright  of
  the emulator some control keys and command line options are unavailable.
  
  Automatic  images can be saved and loaded at any time by pressing  F2  and
  SHIFT + F2 as usual.
  
  You can prevent T3 from loading an automatic image by deleting or renaming
  it  (file name IMAGE.T3), or by using the -a command line option when  you
  run  T3.  This  is  the only permitted command line option  for  automatic
  tasks. Syntax as follows:
  
  -a0                 Ignore any image.
  -a1                 Load any image as an automatic task.
  -a                  Automatic toggle (equivalent to -a0 or -a1 as
                      appropriate).
  
  The following are the only valid control keys for automatic tasks:
  
  F2                  Load image (hold SHIFT to save image).
  F9                  Previous task.
  F10                 Next task.
  F12                 Auto-save image (hold SHIFT to delete task).
  
  Alt-F               Audio resampling frequency control.
  Alt-P               Suspend task (i.e. pause).
  Alt-Q               Audio on/off control.
  Alt-R               Resume task.
  Alt-S               Speed control.
  Alt-V               Audio volume control.
  Alt-X               Task type control.
  
  SCROLL LOCK         Freeze task.
  
  Automatic images have one particularly specialised use; they can  be  used
  to  create  executable PC programs from Dragon/CoCo programs. To  do  this
  proceed as follows:
  
  1.   Run  T3  as  normal, and load the Dragon/CoCo program from an  image,
       snapshot, or virtual cassette.
  
  2.   Use  the emulator control keys to ensure that the cursor keys,  lower
       case,  and  text  colour  task settings are correct  for  the  loaded
       program.
  
  3.   From the title page of the program, press SHIFT + F12 to auto-save an
       image of the program.
  
  4.   You can now create an executable Dragon/CoCo program on a floppy disk
       by typing:
  
                         COPY  T3.EXE  A:\PROGNAME.EXE
                              COPY  IMAGE.T3  A:\
                                       
  5.   PROGNAME.EXE  can be run on any 80386 PC with MS-DOS v4.00  or  above
       and  a VGA graphics adapter. It will start immediately and will  have
       persistent  data each time it is run (thus retaining progress  in  an
       adventure  game,  or preserving hi-score tables in  an  arcade  game,
       etc.).
  
  16   Snapshots
  
  Snapshots  are  minimal task images which are portable  between  different
  Dragon/CoCo emulators, and future versions of T3.
  
  To  load a snapshot into T3 simply press F3 and type the filename  of  the
  snapshot  that you wish to load. If you do not give an extension then  PAK
  will  be  assumed, but snapshots may not always have this extension.  They
  may  also  have  extensions  D32,  D64,  D96  or  CCO  to  indicate  which
  architecture  they are intended for. Snapshots do not contain  BASIC  ROMs
  and  therefore you must ensure that a task is initialised with the correct
  architecture before loading a snapshot. It is usually best to  create  (or
  cold  reset)  a task and wait until it is fully booted  before  loading  a
  snapshot,  otherwise  the  interrupts and IO  registers  may  not  be  set
  correctly.
  
  If  you  load a snapshot with a start address of $C000 then T3 will assume
  that it is a cartridge game and will perform an FIRQ to execute it.
  
  T3  can  load  snapshots in either v1.4 or v1.5 format, as  used  by  Jeff
  Vavasour's CoCo II emulator. It can also load snapshots saved by PC-Dragon
  II  but  only  if  the  format  is v1.4 (or compressed  v1.4).  Any  other
  snapshots  will  need to be converted to v1.4 format before  they  can  be
  loaded  by  T3  (this  conversion can be performed  using  PC-Dragon  II).
  Compatibility with snapshots created by DREaM is untested at the  time  of
  writing.
  
  To  save  a  snapshot press SHIFT + F3 and type in the  filename  for  the
  snapshot. Again if no extension is given then PAK is appended. If the file
  already  exists then you will be given a choice of replacing the  existing
  file or entering a different name.
  
  Snapshots saved by T3 use an uncompressed v1.4 format compatible with Jeff
  Vavasour's  CoCo  II  emulator v1.4 or v1.5, and also with  PC-Dragon  II.
  However,  note  that T3 does not save any emulator settings in  snapshots,
  thus  if you load a snapshot saved by another emulator into T3 and re-save
  it  then you will lose any settings used by the other emulator. Also  note
  that  T3  always  automatically minimises  the  amount  of  RAM  saved  in
  snapshots, which may cause difficulties if you load a T3 snapshot into PC-
  Dragon II and re-save it. To avoid any potential problems always reset the
  snapshot length to $8000 or $FF00 before re-saving a T3 snapshot using PC-
  Dragon II (press F4, 5, 2 and then enter 8000 or FF00 as appropriate).
  
  Beware that because the snapshot format does not include all IO registers,
  you  may sometimes find that you hear no audio when you reload a snapshot.
  This  can  usually be fixed by typing the following BASIC  command  before
  loading the snapshot:
  
                                POKE &HFF23, 63
  
  Since  ROM  is not saved in snapshots, if you are running cartridge  based
  software then you will need to reload both the cartridge and RAM snapshots
  in  order to restore the emulator state using snapshots. In this situation
  it  may  be more convenient to use images, because these include both  RAM
  and ROM.
  
  T3  uses  the same buffer area for snapshots as cassettes, thus  accessing
  the  snapshot  facilities will force any open cassette to be closed.  This
  version  of  T3  does  not  buffer the memory  areas  held  in  compressed
  snapshots,   thus   loading   them  is  quite   slow   and   the   message
  "DECOMPRESSING..." will appear.
  
  17   Multi-Tasking
  
  When  T3 is started it will emulate just one Dragon/CoCo. However, if  you
  have   spare   base  memory  available  then  you  can  create  additional
  Dragon/CoCo  sessions at any time by pressing the F11 key (or INSERT).  T3
  then  spawns and boots a new Dragon/CoCo session (or task) and  moves  the
  previously executing Dragon/CoCo task into the background.
  
  Each  new task is entirely independent of other tasks, receiving it's  own
  RAM,  ROMs  and  emulator  workspace (includes settings,  keyboard  state,
  cassette  buffer, text font etc.). The ROMs for the new  task  are  copied
  from  the  current  task  when the new task is created,  but  the  RAM  is
  cleared.
  
  Once  you have more than one task running under T3, you can switch between
  them at any time by pressing F10 (or PGDN) to switch to the next task, and
  F9  (or  PGUP)  to switch to the previous task. Unwanted tasks  should  be
  deleted  in  the  usual  way by pressing F12 (or  DELETE).  T3  will  then
  terminate the current task and switch to the next remaining task, if any.
  
  In  addition to allowing a variable number of tasks to be created,  T3  is
  also capable of executing the tasks simultaneously. It does so using a pre-
  emptive  multi-tasking  executive  which  switches  context  between   the
  available tasks up to 17 times per second (switching is synchronised  with
  Dragon/CoCo  interrupts in order to reduce game flicker and  is  therefore
  slower for slower PCs). Even on very fast PCs, the multi-tasking may cause
  game motion to be jerky and keyboard responsiveness to be less sensitive.
  
  By  default  all tasks are executed exclusively rather than timesliced  in
  this manner. However, pressing Alt-X when two or more tasks exist causes a
  task  type selection box to appear. The type of the current task can  then
  be  set to either "EXCLUSIVE" or "TIMESLICE". If the type of a task is set
  to  "EXCLUSIVE"  then  it  will not execute at  all  when  it  is  in  the
  background, and will not allow any other tasks to execute whilst it is  in
  the foreground.
  
  By  contrast, if set to "TIMESLICE" then a task will share processing time
  with  any  other  "TIMESLICE"  tasks whenever  any  of  them  are  in  the
  foreground.  Each "TIMESLICE" tasks receives an equal share of  processing
  time  irrespective of their target speed and irrespective of whether  they
  are in the foreground or the background.
  
  Any tasks which are suspended or frozen do not receive a timeslice even if
  they are in the foreground, thus suspending or freezing a "TIMESLICE" task
  may  cause other "TIMESLICE" tasks to execute more quickly (this  will  be
  the  case  whenever a task is currently executing slower than it's  target
  speed).
  
  Note  that because tasks are independent, they each require a lot of  base
  memory  (133K  per  task). This limits the number of tasks  which  can  be
  created  by  T3  to  four for a minimally booted PC, or two/three  for  an
  average  PC  set-up.  Future versions of T3 may allow  more  tasks  to  be
  created (e.g. by allowing ROM sharing, or by swapping exclusive tasks into
  EMS/XMS),  but in the meantime it is of course possible to run  more  than
  four  Dragon/CoCo tasks by using an environment such as MS-Windows or  MS-
  DOS v5.00/v6.00 DOSSHELL in order to run more than one instance of T3.
  
  18   Target Speed
  
  Each  task has an independent target speed setting. T3 assesses the  speed
  of  each task relative to the target setting for every 25 Dragon/CoCo  IRQ
  periods executed (this equates to approximately every half a second if the
  target  speed is 100%). The average instruction execution speed  for  each
  task  is  then  adjusted, where necessary, in order to meet the  requested
  target speed as closely as possible.
  
  Note  that  the  dynamic execution speed adjustments  are  made  in  small
  increments  (or decrements). It therefore takes a few seconds  for  T3  to
  make  any  necessary  speed  adjustments whenever  "TIMESLICE"  tasks  are
  created, deleted, suspended, frozen or resumed.
  
  If the target speed for a task is set to "MAX" then the execution speed of
  that  task  is not measured or adjusted. The task simply runs as  fast  as
  possible.
  
  The dynamic speed adjustment of a task may also be turned off by selecting
  target  speed  "OFF". The delay factor for the task is then fixed  at  the
  current  value  when "OFF" is selected. This is not usually necessary  but
  will give greatly improved music reproduction. Note, however, that if  you
  turn  dynamic  speed adjustment off for a "TIMESLICE" task then  creating,
  deleting,  suspending,  freezing or resuming any other  "TIMESLICE"  tasks
  will have a dramatic impact on the execution speed of the task because  T3
  will not be allowed to compensate for the change in number of tasks.
  
  19   Emulator Compatibility
  
  The  following  table shows T3 compatibility for various platforms.  Where
  "?"  is shown, compatibility is unknown. Where "*" is shown, compatibility
  is  unknown  but has been guessed. If you can provide information  on  the
  details  which  are  unknown, or believe others to  be  wrong,  please  do
  contact me at the address provided at the end of these notes.
  
         Platform           | Run T3 | Long Filenames | Audio
         -------------------+--------+----------------+--------
         MS-DOS v1.xx-v3.xx |   NO   |       NO       |   NO
         MS-DOS v4.xx-v6.xx |  YES   |       NO       |  YES
         Windows 3.1x       |  YES   |       NO       |  YES
         Windows 95         |  YES   |      YES       |  YES
         Windows NT         |  YES   |       NO       |   ?
         OS/2               |  YES   |       NO       |  YES*
         SoftWindows        |   NO   |       NO       |   NO
         DR-DOS             |   NO*  |       NO       |   NO
         Novell DOS v?      |  YES*  |       NO       |  YES*
         PC-DOS v1.xx-v4.00 |   NO*  |       NO       |   NO
         PC-DOS v4.01+      |  YES*  |       NO       |  YES*
  
  20   Frequently Asked Questions
  
  People  ask me a lot of questions about T3 and the Dragon/CoCo  scene,  so
  please  check  to  see if the answer to your question is here  before  you
  write to me. Thanks.
  
  Q.   Where can I download T3 updates?
  
  A.    The  latest  version of T3 is held on my web site.  The  address  is
  "http://public.logica.com/~burginp/t3.html".  Please  feel  free  to  make
  links to this page, but do not link directly to the ZIP file because  your
  link will be invalidated when the ZIP is updated. A new version of T3 will
  be available from SimTel mirror sites in the near future.
  
  Q.   Where on the Internet can I find the ROM files?
  
  A.   You can get the ROM files for the Dragon 32, Dragon 64 and Tandy CoCo
  II  from  at least one site on the Internet. Try Ross Hamilton's web  site
  and David Linsley's web site. You can also find links to these from my own
  web  site,  but for copyright reasons the files are not stored there.  Try
  the                            following                           address
  "http://public.logica.com/~burginp/emulators.html#roms".
  
  Q.   Why don't you include the ROM files?
  
  A.    I  don't  include them because I have no right to do  so.  They  are
  copyrighted,  and  as  much as we may dislike it, that  copyright  remains
  valid.  I  agree  that  it  is very unlikely that  I  would  be  sued  for
  infringing the copyright, but that is my risk and I choose not to take it.
  Also,  including the ROMs in the emulator ZIP would force  any  person  or
  site distributing the emulator to infringe the same copyright, which would
  be  unfair on them. Moreover, some archive sites (including SimTel)  would
  not  accept  T3  if  the ROMs were included. If you did receive  the  ROMs
  together with the emulator then please drop me a line at the address given
  at the end of these instructions.
  
  Q.   Why won't my ROM work?
  
  A.    This problem is almost always caused by your ROM file being corrupt.
  You should obtain another copy, ensuring that you download in binary mode.
  
  Q.   Why won't the keyboard/joysticks work in <game>?
  
  A.    This problem is usually caused by the game taking exception  to  the
  fact that by default T3 allows the PC cursor keys (standard and keypad) to
  simultaneously emulate both the Dragon/CoCo joysticks and the  Dragon/CoCo
  cursor keys. The solution is to use the Alt-C control to set the PC cursor
  keys  to  emulate either the Dragon/CoCo joysticks only or the Dragon/CoCo
  cursor keys only.
  
  Q.   How do I load this *.CAS format software into T3?
  
  A.    If the program is machine code format, type "CLOADM". This will work
  for  most  software. If the OK prompt appears after loading then you  will
  need  to  type  "EXEC". Remember to always perform  a  cold  reset  before
  loading  each game into T3. If you still get unexpected results then  your
  *.CAS file is probably corrupt. For software written in BASIC type "CLOAD"
  and then "RUN".
  
  Q.    How  do  I  load  this *.PAK, *.D32, *.D64, *.D96  or  *.CCO  format
  software into T3?
  
  A.    These extensions all indicate that the files snapshots. If they  are
  v1.4  or v1.5 format (there's no way to tell) then they can be loaded into
  T3  by  using the snapshot facilities (F3 key). If they are other versions
  then  you will first need to use the PC-Dragon II emulator to convert them
  to v1.4 format.
  
  Q.   How do I load this *.IMG format software into T3?
  
  A.   You can't. This software is an old T3 image, which is not portable to
  this version of T3. Your only chance of loading it into the new version of
  T3 is by converting it into a virtual cassette file (may not be easy).
  
  Q.   How can I load my old tapes into T3?
  
  A.    There are a few utilities around which enable tapes to be copied  to
  files  on  your  PC  by  using a SoundBlaster  card.  Download  the  older
  emulators  (PCDGN201.ZIP  and COCO2-15.ZIP)  and  read  the  documentation
  provided there.
  
  Q.   How can I load my old disks into T3?
  
  A.   You can't. T3 does not support disk drive emulation. Your only option
  is  to  transfer the software to another format (such as a cassette  file)
  and  use  that. This is only possible for a small number of programs.  You
  can transfer files from Dragon disks to PC disks using PC-CONVERT (contact
  NDUG), and from CoCo disks using COCO2-15.ZIP. Raw disk format files  held
  in  PC  format  can  be  converted  to  cassette  files  using  DC.EXE  in
  PCDGN201.ZIP.
  
  Q.   Where can I get a copy of <some game>?
  
  A.    For Dragon games check Ross Hamilton's archive, a link to which  can
  be         found         on         my         web         site         at
  "http://public.logica.com/~burginp/dragon.html". If  you  can't  find  the
  game  there then you will have to convert it to PC format yourself. Please
  don't ask me to send it to you.
  
  Q.   Where can I buy hardware these days?
  
  A.    I  do not keep information about hardware suppliers, and cannot help
  with this type of enquiry.
  
  Q.   Please help me with OS9, or with my Tandy <machine>?
  
  A.    I  have  no  knowledge of these, sorry, and  cannot  help  with  any
  enquiries.
  
  Q.   Can I still register PC-Dragon II?
  
  A.    Yes you can. At the time of writing, the terms and conditions of the
  original   registration  offer  are  unchanged.  Please   refer   to   the
  documentation  provided in PCDGN201.ZIP. However, please note  that  snail
  mail  should  not  be  sent to the address given there.  Instead  use:  18
  Moorcroft Road, Sheffield, S10 4GS, England.
  
  21   Disclaimer
  
  If  you  choose  to use T3 then you do so entirely at your  own  risk.  No
  warranty either implied or otherwise is provided for this software.  Usage
  of T3 constitutes acceptance of these terms.
  
  22   Usage Restrictions
  
  T3  v0.8  is released to the public domain. It may be used and distributed
  without  charge,  but  MUST  NOT be uploaded to  FTP  sites/WWW  sites  or
  bulletin   boards.  T3  v1.0  will  be  made  available   for   widespread
  distribution very soon, but until then I would like it to reside  only  at
  "http://public.logica.com/~burginp/t3.html".
  
  23   Address For Comments And Bug Reports
  
  If  you  have  any  comments on T3 please do drop  me  a  message  at  the
  following  address "BurginP@Logica.Com". If you are reporting a  bug  then
  please  include as much information as possible (but please  do  not  send
  binaries).
  
  If you have access to the World Wide Web then please refer to the notes at
  "http://public.logica.com/~burginp/mail.html" before  sending  me  any  e-
  mail.
  
