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# Tandy 2000 HD

[date: 2014]

I find this to be a very interesting system:  It can run a multiuser operating system (Xenix), it's one of very few machines based on the Intel 80186, it looks cool on the the stand... and it was generally considered a flop.

## The System



TODO serial number

I also have a non-HD Tandy 2000, although it's currently used mostly as a test system:



TODO serial number

## Restoration

I have done a complete restoration on this system (although like an old car, there's always something more to do.)

I purchased the original system off of eBay somewhere around 2006.  It was missing the floppy drives, was dirty, and sometimes wouldn't boot.  I did a complete tear-down and rebuild of the system.  Every part has been cleaned, tested, and replaced if necessary.

Here's a list of some of the things I've done, and others I still plan to do:


  fails to boot the machine, after it has been on for a while and warmed up.  After turning it off and letting it cool down, it works okay again for a while.  HFORMAT does not fix it.  Want to try a new low-level format.


### TODO



## Hardware Options

### Memory

128k on daughtercard.

128k on secondary daughtercard (part #26-5160).  (total 256k)

Expansion board (part #26-5161) with 128k.  Added 128k (part #26-5162).  (total 512k)

I have upgraded the 128k/256k memory expansion board with another 18 DRAM chips, to bring the total RAM from 384k to 512k.  Part #41662, "IC,DRAM,4164-150", from <a href="http://www.jameco.com">Jameco</a>.  This part is listed as "major brands", yet I was lucky to receive like-new chips made by Texas Instruments, so they're a perfect match to the original chips.

TMS4164-Z15NL

AP8414

18 pcs


Two expansion boards can be used.  (total 768k)

As I have been reversing the BIOS, I have found incomplete evidence of supporting up to 896k.  The Tandy 2000 FAQ mentions the Envision Design board which supported up to 896k.

;; Detect amount of memory

cld

mov bh, 0xe ; At most 14 banks (=896k) supported {ODD TRM says 784k}

mov bl, 0x0 ; but zero 64k banks detected so far.


### Hard Drive

The Tandy 2000 HD shipped with the Tandon TM502 10 MB MFM hard drive.

#### Formatting

Low level formatting:

How to do a low level format?  The HD controller board does not have a ROM with a low-level format routine.  The HFORMAT.COM that ships with the machine apparently is only a high-level format.  One alternative is to transfer the drive to another machine and do the low level format there.

HFORMAT parameters:



### Floppy Drives

Quad Density.

From the factory, the floppy drives' LEDs would both light when either was accessed.  See bulletin 2000:010 for the fix.  (TODO: post pictures...)

### Service Bulletins

The Tandy 2000 had many service bulletins issued.  Some of these hardware bugs were triggered by running Xenix.

## Firmware

### Versions

Known versions of the firmware:



TODO: changes, CRCs, dates, downloads

### Commented Source

Very little software was written for the Tandy 2000, and it was not well supported by Radio Shack.  To better understand how to write to the machine, I decided to reverse engineer the BIOS (specifically, the firmware on the EPROMs).

Download the version 2.00.00: <a href="t2k_bios_2.00.00.asm">commented assembly</a>.

This is a work in progress.  Comments and clues welcome.

### Bugs

So far during the reversing of the BIOS, I've discovered the following bugs (noted by `{BUG...}` in my disassembly):



### Updates

Would be fun to fix a few bugs in it and release an updated binary.

## Software

### System

<a href="images/Tandy2000HD-MSDOS2.11.03-BIOS2.02.00-disk1.td0.xz">MS-DOS 2.11.03 with BIOS 2.02.00.xz</a><br>
<a href="images/Tandy2000Diagnostics-2.0.imd.xz">Tandy 2000 Diagnostics</a><br>
<a href="images/Tandy2000DIGIMouse-1.0.imd.xz">DIGIMouse driver disk</a><br>
<h3>Applications</h3>
<a href="images/OpenAccess-t2k-disk1.imd.xz">OpenAccess-t2k-disk1.imd.xz</a><br>
<a href="images/OpenAccess-t2k-disk2.imd.xz">OpenAccess-t2k-disk2.imd.xz</a><br>
<a href="images/OpenAccess-t2k-disk3.imd.xz">OpenAccess-t2k-disk3.imd.xz</a><br>
<a href="images/MultiMate-3.02-Tandy2000.imd.xz">MultiMate</a><br>
<h3>Games</h3>
Planetfall<br>
Leather Goddess of Phobos<br>
<h3>Development</h3>
<a href="images/MicrosoftPascal-3.13-Tandy2000.imd.xz">MS Pascal</a><br>
<a href="images/MicrosoftMASM-1.1-Tandy2000.imd.xz">MS MASM</a><br>
<h3>...</h3>
<a href="images/">more...</a>

## Documentation

(Some of this is mirrored from Rich Cini.)

<a href="doc/Introduction to the Model 2000.pdf">Introduction to the Model 2000</a><br>
<a href="doc/Reference Guide for the Model 2000.pdf">Reference Guide for the Model 2000</a><br>
<a href="doc/Tandy 2000 Color Chip Kit Install Manual.pdf">Color Chip Kit Install Manual</a><br>
<a href="doc/Tandy 2000 Hard Disk Supplement.pdf">Hard Disk Supplement</a><br>
<a href="doc/Tandy 2000 MS-DOS Manual.pdf">MS-DOS Manual</a><br>
MS-DOS 2.11.03 Notes<br>
<a href="doc/Tandy 2000 Programmer's Reference.pdf">260-5403: Programmer's Reference Manual</a><br>
<a href="doc/Tandy 2000 Technical Reference.pdf">Technical Reference</a><br>
<a href="doc/t2k_serv_bulletins.pdf">Service Bulletins</a><br>
DIGIMouse / Clock Manual<br>
4-port Serial Expansion Board Manual<br>

=> doc/  More documentation...

## References

=> t2kfaq.txt Local copy of Jeff Hellige's "Tandy 2000 FAQ version 2.3"
=> http://www.cchaven.com/T2000.HTML Jeff Hellige's Tandy 2000 page
=> http://www.old-computers.com/museum/computer.asp?st=1&c=1219 Description at old-computers.com
=> http://www.classiccmp.org/cini/tandy2000.htm Rich Cini's T2k restoration
-> http://oldskool.org