Tand-Em -- The PCjr and Tandy 1000 Emulator

Tand-Em Copyright (c) 1998-1999, Vincent Joguin

Documentation Copyright (c) 1998-1999, Jim Leonard

Version 0.55 - 19991803

The latest version of this document is always kept at:

Table of Contents


Tand-Em 0.55 is still in an early alpha stage, so please expect many bugs! This program is delivered "as is" and neither Vincent Joguin nor Jim Leonard can be liable for any damage it could do to your computer.

This program must not be sold by any way, but it can still be distributed on shareware CDs as long as there are no financial benefits received from the act of selling it. You are highly encouraged to copy this emulator as long as it remains in its original, zipped form. This program must not be modified in any way.

Tandy 1000 is a registered trademark of Tandy Corporation/Radio Shack. PCjr is a registered trademark of IBM Corporation. Sierra is a registered trademark of Sierra On-Line, Inc. Sound Blaster is a registered trademark of Creative Labs Inc. All other trademarks are owned by their respective companies.


Welcome to Tand-Em! Tand-Em is a Tandy 1000 and IBM PCjr emulator. The PCjr and Tandy 1000 were 8088-based PCs that had enhanced graphics and sound well before EGA or Adlib came out, and due to the Tandy's popularity in the states, many games (well over 200) were programmed to take advantage of those enhanced graphics and sound. Some particular early games have hidden graphics and music that non-PCjr and non-Tandy owners have simply never seen or heard!

Now that most of those machines are gone, the only way to experience these great old programs is through some sort of emulation. That's where Tand-Em comes in: Tand-Em fully emulates a 8088 or 80188, and uses a V8086 "window" to access 8087 instructions if programs require a math coprocessor. Through exact emulation of an 8088 via software, exact speed throttling and redirection of ALL port writes and memory accesses are now possible, and are able to be translated to another format (Tandy graphics to EGA, for example) or completely emulated (Tandy's TI-SN76496 3-voice sound chip).

Because of Tand-Em's reliance on 80386 protected mode, Tand-Em requires an 80386 or higher CPU (or compatible).

For more complete information on the PCjr and Tandy 1000, including an illustrated history, visit The Oldskool Shrine to The IBM PCjr and Tandy 1000 located at http://www.oldskool.org/shrines/pcjr_tandy/.

What's new in 0.55:


Tand-Em is a cycle-exact, opcode-exact, BIOS-exact emulator. As such, it requires a "dump" of a Tandy 1000 BIOS ROM (or, in a future release, an IBM PCjr ROM) in order to fully emulate a Tandy (or PCjr). In addition, Tand-Em has its own protected-mode CPU and memory manager, so it must be used under a clean DOS boot.

To prepare Tand-Em for use, you must go through a couple of preparatory procedures, some of which require an actual Tandy and a method for getting files off of a Tandy and onto the machine running Tand-Em. (For getting files to/from your Tandy, you can use a network card, serial or parallel cable, or simply put a 5.25" drive into your modern PC.) You must:

...before you run Tand-Em. Let's go over these steps in detail:

  1. Boot to pure DOS, with no memory managers like EMM386.EXE or HIMEM.SYS. No Windows 95/98/NT, please--they throw the machine into protected mode and prevent Tand-Em from working; if you have Windows 95/98, you must press shift-F5 at boot time in order to run Tand-Em. The same goes for x86 protected-mode emulators, like dosemu--they already run in protected mode and interfere with Tand-Em. (True software-only 80x86 emulators like Bochs or SoftPC may work, but they've never been tested.)
  2. Copy the program JROMRIP.COM (located in the UTILS subdirectory of the Tand-Em distribution, along with other utilities you'll need) to your Tandy and run it. This will dump your Tandy's ROM into a file. Copy the resulting file (.ROM) back to your PC and into your Tand-Em directory.
  3. Copy the program DISK2FDI.EXE over to your Tandy and run it to copy a 360KB disk into a raw diskette image file (.FDI). Copy this image file back to your PC.
  4. Use the program FDI2DISK.EXE to copy the image file onto a high density formatted disk of any kind located in drive A:.
  5. Leave this disk in drive A: and execute JR.EXE. Remember not to have any memory manager installed.

You should see your PC transformed into a Tandy, looking exactly like what you see when you boot your Tandy computer--right down to 40-column textmode. :-)



The following keys can be pressed at any time to control Tand-Em during execution:


You can execute DOS and many programs (games, music software, graphics software, etc.) in either CGA or Tandy graphic modes. Tandy video modes will be emulated through your EGA/VGA card. Please understand, however, that Tand-Em is still in the alpha stage, and nothing is guaranteed to work!

Tand-Em perfectly emulates Tandy's TI-SN76496 3-voice sound chip using your Sound Blaster, Sound Blaster Pro, or Sound Blaster 16 (or compatibles). Emulation is nearly perfect, with digital synthesis for the noise channel and mixing actual sampled waveforms for the sound/music channels. (The DAC of the TL/SL series is not yet implemented; this will be addressed in a future release.)

(For those without a Sound Blaster or compatible, Tand-Em can emulate Tandy sound through a Yamaha FM OPL3-compatible sound board, like an Adlib Gold. With a regular OPL2 board, such as the original Adlib, it might work, but it hasn't been tested. Right now the OPL3 sound emulation is very fast, but is inaccurate; the noise channel is very simple, and the Tandy's frequency waveform is only approximated. Since used Sound Blaster cards are very cheap, we recommend obtaining one for best emulation quality.)

Tand-Em's control menu lets you change Tand-Em's operation. The emulated processor (8088 or 80188), its speed, and the selected ROM image can be changed in the configuration menu. You can also toggle the usage of hard drives C: to Z: and joystick support. (Please note that while you will be able to copy the files off of hard drives, you cannot execute programs directly off of them. You will need to copy the executable files to a floppy disk in drive A: in order to get them to execute. For example, COPY GAME.EXE A:, then A:GAME, while staying in the game's directory on C:)

Hint: When changing the CPU speed in the configuration menu, holding down the ALT key when hitting left-arrow and right-arrow makes the values jump in larger increments.

Frequently-Asked Questions

Q: I don't have a Tandy--can't you just give me the ROM?
A: No. Doing so would be a violent breach of Tandy Corporation's copyright. ROMs may be dumped and used for whatever you like as long as you own the original. If we simply give you the ROM, we could be sued! Remember: All emulators are legal, but ROM trading is not.

Q: If I need an original Tandy to dump the ROM, why bother writing the emulator when I'll have a real Tandy in front of me?
A: Because your Tandy may eventually fail to work! With Tand-Em, you can continue to play your favorite old games, run your great old music software, etc. on modern PCs that can be repaired easily.

Future Development

There's still work to be done on Tand-Em, which we haven't gotten to for one of two reasons: We don't have the knowledge to implement a feature, or we've run into problems trying to implement it. See the Contributions and Contact Info section at the end of this document to help!

Contributions and Contact Info

For comments, contributions, suggestions, etc. contact Jim Leonard.