|This article does not cite any references or sources. (December 2007)|
|Operating system||MS-DOS; Xenix|
|CPU||Intel 80186 @ 8 MHz|
|Memory||128 KB - 768 KB (896KB w/mods)|
The Tandy 2000 was a personal computer introduced by Radio Shack in late 1983 which used the 8 MHz Intel 80186 microprocessor. By comparison, the IBM PC XT (introduced in March 1983) used the older 4.7 MHz 8088 processor, and the IBM PC AT (introduced in 1984) would later use the newer 6 MHz Intel 80286. Due to the more efficient design of the 80186, the Tandy 2000 ran significantly faster than other PC compatibles on the market, and slightly faster than the PC AT. (Later, IBM upgraded the 80286 in new PC AT models to 8 MHz.)
While touted as being compatible with the IBM XT, the Tandy 2000 was different enough that most software that was not purely text-oriented did not work properly. It differed by having a Tandy-specific video mode (640x400, not related to or forward-compatible with the 1987 VGA standard), keyboard scan codes, and other differences.[clarification needed] The computer was poorly supported by Radio Shack in the following years; eventually the remaining unsold computers were converted into the first Radio Shack Terminals (which coincidentally had been one of the backup plans for the original TRS-80 Model I).
The Tandy 2000 was the only computer sold by Radio Shack that had both the "Tandy" and "TRS-80" logos on its case, marking the beginning of the phaseout of the "TRS-80" brand.
- 8 MHz Intel 80186
- 128KB RAM (expandable to 768KB, of which up to 256KB was located on the motherboard, or up to a maximum of 896KB with motherboard and ROM modifications)
- 1 or 2 720KB 5¼" floppy drives
- 10MB MFM full-height hard drive (upgradable to two 32MB half-height drives, or two 80MB drives with ROM modifications and third-party low-level formatting software)
- Proprietary parallel printer port (requires adapter cable to connect to a Centronics-port printer)
- Proprietary serial port
- 4? card slots on the back could accept expansion boards without the need to open the case
- 256KB RAM card (up to 2 could be added for 768KB total; each card had two 128KB banks of nine 16KB RAM chips)
- Color Graphics Card
- Mouse/Clock Card
- Hard disk card with two ribbon cables to an outboard 10MB hard drive
- Network Card (BNC)
Compatibility issues 
The Tandy 2000 was nominally BIOS-compatible with the IBM XT, which allowed well-behaved DOS software to run on both platforms. However, most DOS software of the time bypassed the operating system and BIOS and directly accessed the hardware (especially video and external ports) to achieve higher performance, rendering the software incompatible with the Tandy 2000.
The Tandy 2000's proprietary graphics hardware allowed a display of up to 640x400 (non-interlaced) pixels with 16 colors onscreen, which was a particularly high-resolution and colorful display for its day. CGA compatibility was hit or miss. The text-mode address space was in a different location but third party memory-resident software hacks remedied this by copying the PC-compatible text-mode memory to the Tandy 2000's text space at a rate of 5-10 times per second. This caused a bit of choppiness in the display, but worked fairly well. Color Monitor CM-1 listed for ~$799 and required a $300 color display card in one of the 5 card slots. Green Screen VM-1 for ~$300 was used without the color display plug in card and gave a very fast text display rate, a 'HOLD' key on the keyboard could be used to pause text output as it was much too fast at times.
Serial port 
The serial port hardware was completely different from the PC-XT's. PC-compatible terminal emulation software had to either maintain strict BIOS usage of the serial hardware, or else use a FOSSIL driver, which was a software wrapper that virtualized the serial hardware (see also DEC Rainbow), allowing the terminal software to work on a wider variety of hardware. Luckily many terminal programs were available for the Tandy 2000 and many were used to log on to BBS's, e-mail, etc.
The Tandy 2000 used quad-density 5.25" floppy disks formatted at 720k. This format type (80 track disks at the double-density bitrate) was not used by PC compatibles, although some CP/M machines and the Commodore 8050/8250 drives had them. Normal PCs of the time had 40 track double density floppy drives and could not read quad density due to the drive heads being too wide to read the narrower tracks. 1.2MB 5.25" drives (introduced on the IBM AT) could read quad density disks as they were 80-track and had thinner heads. Various utility programs for DOS existed that allowed nonstandard format types such as the Tandy 2000's disks to be read. Much like 1.2MB drives, the Tandy 2000 had problems reliably writing 360k PC disks due to the smaller heads not completely erasing the tracks and causing 40-track drives to become confused by residual magnetic signals on the outer edge of the track.
The floppy controller on the Tandy 2000 will accept 3.5" floppy drives, although as it does not support high density, they can only be used as 720k disks.
Operating system 
The Tandy 2000 required a specific version of MS-DOS that would run only on this machine. Standard MS- or PC-DOS (for generic IBM-compatibles) would not run on a Tandy 2000. It was standard practice and Microsoft's expectation at the time that a customized version of MS-DOS would be prepared for each different machine, with I/O drivers designed for the hardware of that model. The highest version of DOS that Tandy Corporation released for the Tandy 2000 was 2.11.03, with a few minor 3rd-party patches after the fact. A modified version of Windows 1.0 was able to run on the Tandy 2000.
Software packages that were released for the Tandy 2000, included WordPerfect 4.2 (WP5.1 could work with software patches), Lotus 1-2-3, AutoCAD, Lumena (from Time Arts) and shareware office programs. Microsoft released a version of Xenix for the Tandy 2000 (used with Tandy's network card).[clarification needed] Better BASIC for both the T2K and the PC was used to write BBS software for the T2K and later ported to the IBM-pc. Radio Shack's 'DESKMATE' was used with the T2K and the Tandy-1000
End of life 
After Tandy dropped support of the Tandy 2000, a group of users formed the Tandy 2000 Orphans, with software reviews, software and hardware hacks, and a shareware/freeware repository. There was also a BBS based in Texas that had an extensive library of compatible software available for download; neither the BBS nor its web-based descendant is active today. FAQ @ CCHAVEN.COM