Tandy 2000

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Tandy 2000
Type Personal computer
Release date 1983; 42 years ago (1983)
Discontinued 1988
Operating system MS-DOS; Xenix
CPU Intel 80186 @ 8 MHz
Memory 128 KB - 768 KB (896KB w/mods)
Predecessor TRS-80 Z80-based series
Successor Tandy 1000 series

The Tandy 2000 is a personal computer introduced by Radio Shack in September 1983 based on the 8 MHz Intel 80186 microprocessor running MS-DOS.[1] By comparison, the IBM PC XT (introduced in March 1983) used the older 4.77 MHz 8088 processor, and the IBM PC AT (introduced in 1984) would later use the newer 6 MHz Intel 80286. Due to the 16-bit wide data bus and more efficient instruction decoding of the 80186, the Tandy 2000 ran significantly faster than other PC compatibles, and slightly faster than the PC AT. (Later IBM upgraded the 80286 in new PC AT models to 8 MHz, though with wait states.) The Tandy 2000 was the company's first computer built around an Intel x86 series microprocessor; previous models were built around the Z80 and 68000 CPUs.

While touted as being compatible with the IBM XT, the Tandy 2000 was different enough that most existing PC software that was not purely text-oriented failed to work properly.

The Tandy 2000 and its special version of MS-DOS supported up to 768 KB of RAM, significantly more than the 640 KB limit imposed by the IBM architecture. It used 80 track "quad density" floppy drives of 720 KB capacity; the IBM standard was only 360 KB.

The Tandy 2000 had both "Tandy" and "TRS-80" logos on its case, marking the start of the phaseout of the "TRS-80" brand.

History

File:Tandy 2000 Ad, BYTE, July 1984.png
Ad in Byte magazine, July 1984, co-marketing MAI/Basic Four software

The introduction of IBM's Model 5150 Personal Computer in August 1981 created an entirely new market for microcomputers. An entire new industry came into being as a great number of new hardware and software companies were founded in dedication to this single platform.

By this date Tandy/Radio Shack had been in the small computer market for four years, since its August 1977 introduction of the TRS-80 Model I. Buoyed with its instant success, the new computer division followed in October 1979 with the TRS-80 Model II -- a business-oriented system with 8 inch floppy drives and a professional keyboard and screen, and a much larger price tag. The Models 12 and 16 succeeded the TRS-80 Model II, adding high-end features like hard drives, networking, specialized software packages for accounting, legal, and medical businesses, and the Motorola 68000 CPU running Microsoft Xenix OS.

Tandy's motive for moving into the new MS-DOS domain were twofold: first to capitalize on the new market, and second to leverage sales opportunities afforded by Tandy's solid position in the small business computer market. It was believed by marketing management that many Tandy customers using the Models 12 and 16 would prefer to stay with Tandy products when (inevitably, it seemed) they made the jump onto the burgeoning IBM/Microsoft bandwagon. Therefore, Tandy would have to produce an IBM style computer running the now industry-standard MS-DOS.

Several other big-name computer manufacturers made the same leap: Wang Laboratories had its Wang PC, Texas Instruments had its TI Professional Computer, and Digital Equipment Corporation had its DEC Rainbow. Newcomer Compaq had its Compaq Portable. Except for the Wang, which used the Intel 8086, all these early clones used the same 8-bit 8088 microprocessor as the IBM PC, and were incompatible at the hardware level (with the important exception of the Compaq). Computing performance of all these copycat machines was no or little improvement over the new IBM standard; they competed strictly on having lower prices, and like Tandy, exploiting their pre-installed base of customers.

At this time the planners at Tandy/Radio Shack made the decision to set themselves apart from the pack of PC imitators by producing a computer of superlative performance while being competitive in price. All along since their entry into the market in 1977, this had been Tandy's forte. Tandy was well positioned to expand its sales opportunities, it was calculated, because of its large base of customers in both the consumer and business markets (with its Z80-based TRS-80s and 68000-based Models 12 and 16, respectively). The new machine would be aimed at the middle ground between these two market segments, hopefully without cannibalizing existing product lines in either.

This strategy is the genesis of the Tandy 2000's top-drawer specification: Intel 80186 CPU (never before used in a mass-market PC), maximum 768 KB RAM, high capacity floppy drives, and vivid high-density graphics display.

Two models of Tandy 2000 were first introduced: a dual drive floppy-only model for $2750 and the 2000HD with a single floppy drive and a half-height 10 MB hard drive for $4250. The dual floppy model had 128 KB RAM and the hard drive 2000HD had 256 KB.[2]

The computer received a lukewarm welcome by the market and the computer press because of its inability to run most popular MS-DOS applications. Though Radio Shack supported the machine with hardware add-ons and software tailored specially for it (including some of the most popular programs like Lotus 1-2-3), the computer failed to gain popular acceptance and was never developed further. Instead Tandy/Radio Shack turned its engineering efforts to the PCjr-compatible Tandy 1000, which proved more successful in the market.

The Tandy 2000 was marketed through early 1988 with continual price cuts.[3] Eventually they were closed out for $999 and 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).

Specifications

  • 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 hard drive (upgradeable 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)

Four card slots on the back could accept expansion boards without any need to open the case, using a rail system. Available expansion boards/cards included:[4]

  • 256KB RAM card (1 or 2 could be added for 768KB total; each card had two 128KB banks of nine 64 KB DRAM chips type 4164)
  • Monochrome Graphics Card with optional color graphics expansion (Tandy VM-1 or CM-1 monitor required)
  • Serial I/O expansion board providing four RS-232 ports (proprietary driver software required)
  • Hard disk controller card with two ribbon cables to an outboard 10MB hard drive
  • Mouse/Clock controller, including both a mouse controller and a battery-backed time/date clock
  • Network card (BNC)
  • Intel 8087 math co-processor card

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.

Graphics

The base Tandy 2000 supported only a text display mode. 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. It gave a very fast text display rate—often too fast to read, but a 'HOLD' key on the keyboard could be used to pause text output.

The display was upgradeable to support graphics via the Tandy 2000 Graphics Adapter, a circuit board that fitted into an expansion slot. It had its own connector for the monochrome VM-1 monitor (~$300); the connector in the rear of the computer cabinet for the text monitor was disabled with this option. The graphics resolution was 640x400 and supported bright text characters. The raster image for each text character was maintained in RAM and could be modified by the user.

Color capability was provided by the Color Graphics Option, which was a set of chips that were inserted into the empty sockets on the monochrome Graphics Adapter provided for this purpose. The Color chipset comprises 16 readily-available chips: eight 4416-15 DRAMs, four 74F245s, and four 25LS22 chips. A trace cut on the graphics board was also required.[5] Resolution for the color board was the same 640x400, non-interlaced, and eight colors of a palette of sixteen available colors were displayable on the Tandy CM-1 monitor (~$799). This was a particularly high-resolution and colorful display for its day. CGA compatibility was hit or miss.

There are only three non-Tandy monitors that will work with the Tandy 2000 graphics card, and they are long out of production. These were the original (1986–88) Mitsubishi Diamond Scan, and the Nippon Electronics Corporation (NEC) Multisync and Multisync GS (Grey Scale).[6] The required horizontal scan frequency for the Tandy 2000 is 26.4 KHz. Modern flat-screen multisync computer monitors cannot sync at frequencies below 30 KHz. The CM-1 monitor is also digital RGB; all modern color monitors are analog only.

Media

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. Tandy distributed the computer with a utility called PC-Maker that would format 40-track disks in the 2000's 80-track drives, and were readable in drives on ordinary PCs.

The floppy controller on the Tandy 2000 will accept 3.5" low density 720 KB floppy drives.

As of May 2016, there is an abandonware site (Vetusware.com) that has available for download a disk image for the latest version of MS-DOS for the Tandy 2000. It includes instructions for using the IBM 1.2 MB 5.25 inch disk drive (80 track) to create a system disk bootable in the Tandy 2000 5.25 inch drive.[7] This procedure can also be used to create a bootable 3.5 inch system disk using an ordinary 720 KB 3.5 inch PC drive; this will boot a Tandy 2000 with its 5.25 inch boot drive replaced with a like 3.5 inch PC drive.

Keyboard

The keyboard was an entirely new design made expressly for the Tandy 2000. It would later be the same keyboard shipped with the Tandy 1000 and its successors.

The arrangement of the function keys was changed from that of the IBM PC/XT, which had ten on the left hand side of the keyboard in two columns of five. Tandy was one of the first PC manufacturers to change this to the modern arrangement of twelve function keys arranged horizontally across the top. IBM gave a nod to the new standard by making this its arrangement for the PC-AT keyboard.

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, a software wrapper that virtualized the serial hardware (see also DEC Rainbow), allowing the terminal software to work on a wider variety of hardware.

Several terminal programs were available for the Tandy 2000, making it possible to log on to BBS's, e-mail, and other remote systems.

Operating system

The Tandy 2000 required a specific version of MS-DOS that would run only on this machine. Standard MS-DOS 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.

MS-DOS for the Tandy 2000 resided entirely in RAM, unlike the IBM PCs which contained the BIOS portion of the OS in ROM. The complete MS-DOS system (BIOS and BDOS) occupied about 53 KB of RAM.[8] This means that the RAM required to run applications on the Tandy 2000 was a little greater. However, the Tandy 2000 fared better in comparison to the later IBM PC-AT in that the AT was required to run MS-DOS version 3.x in order to operate its 1.2 MB floppy drives and hard drive. Version 3 of MS-DOS was rather larger than Version 2.x running on the Tandy 2000. It also proved advantageous that the Tandy 2000's OS resided entirely in RAM and therefore could be updated and hacked with rather less effort.

The Microsoft BASIC interpreter was supplied with the computer. It was highly customized for the Tandy 2000 hardware, particularly its high resolution color graphics. Although IBM produced the Enhanced Graphics Adapter a little more than a year later (October 1984), the Microsoft BASIC interpreter would not support its greater color and resolution capabilities until 1988.

Tandy/Radio Shack produced print advertising featuring Bill Gates of Microsoft extolling the superior performance of the Tandy 2000 and how it was advantageous in Microsoft's development of Windows 1.0.[9]

Software

Software packages that were released for the Tandy 2000 included WordPerfect 4.2 (WP5.1 could work with software patches), Lotus 1-2-3, Ashton-Tate's Framework (office suite), DBase, MultiMate, Pfs:Write, AutoCAD, Lumena (from Time Arts) shareware office programs, and the complete line of Microsoft language products. Microsoft released a version of Xenix for the Tandy 2000 (used with Western Digital's ViaNet network card, distributed by Tandy).[citation 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 also used with the Tandy 2000 and the Tandy 1000.

MicroPro's Wordstar (versions 3.3 and 4.0 only) would run on the T2K provided the user ran the WINSTALL installation utility and, when prompted for the type of video display to be used, selected "ROM BIOS". While this would result in a functional installation, none of the T2K's special features would be operative.[10]

The only version of Lotus 1-2-3 offered for the Tandy 2000 was Release 1A. This was customized to take advantage of the unique hardware of the computer, including its full 768K of RAM, high resolution color graphics, and two extra function keys.

Release 1A's executable code was about 60 KB smaller than the later Release 2, which provided greater macro programming facilities. This extra space for data, with the additional 128 KB of RAM available to a fully expanded Tandy 2000, made it possible to construct larger worksheets than later PCs running Release 2 (until the advent of machines with Expanded memory). For nearly two years following its introduction, the Tandy 2000 was the top performer for processing large models in Lotus 1-2-3.

The Tandy 2000's 720 KB floppy drives were a distinct advantage for running Lotus, because they were large enough to store even the largest worksheets on a single diskette. This is in stark contrast to the IBM PC with its 360 KB floppy disks. In order to store his largest worksheets, a PC user would have to segment them and store them on two disks -- and then he'd have to recombine them in memory later. Although the XT had a hard drive that could store large Lotus worksheets in a single file, the user could not rely on a single hard disk device for permanent storage of important data files; again he'd be forced to segment worksheets for storage on separate disks. The Tandy 2000's large capacity floppy disks made backup maintenance relatively effortless.

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. It was discovered by amateur programmers that many commercial MS-DOS applications needed only minor modifications to function on the Tandy 2000's unique hardware.

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.

See also

References

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