Radio Shack Tandy 2000 дербес компьютері

Personal computer by Radio Shack

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. By comparison, the IBM PC XT (introduced in March 1983) used the older 4.77 MHz Intel 8088 processor, and the IBM PC/AT (introduced in 1984) would later use the newer 6 MHz Intel 80286. Due to the 16 bit 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 used the Zilog Z80 and Motorola 6809 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 double sided quad density floppy drives of 720 KB capacity; the IBM standard at the time of the introduction of the Tandy 2000 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.

The Tandy 2000 was nominally BIOS compatible with the IBM XT, so well behaved DOS software ran 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. This rendered such software incompatible with the Tandy 2000.

The base model Tandy 2000 supported only a text mode display in monochrome. The Tandy VM 1 monitor used the 8 pin DIN video port on the computer's rear panel. 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 sometimes caused some choppiness in the display. It produced a fast text display rate—often too fast to read—but the 'HOLD' key on the keyboard could be used to pause text output. The bit pattern for each text character's raster image was maintained in RAM and could be modified by the user. With clever programming the display's ability to present fine lines provided by the 640x400 screen resolution could be accessed in text mode even without the optional graphics board. The display was upgradable to support pixel addressable graphics via the Tandy 2000 Graphics Adapter, a circuit board that fit into an expansion slot. It had its own connector for the monochrome VM 1 monitor; the video connector in the rear panel cabinet was disabled when this expansion board was installed. The graphics resolution was 640x400 and supported high intensity pixels. 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. Resolution for the color board was the same 640x400, non interlaced, and eight colors out 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. The CM 1 accepted, as input from the color graphics board, digital RGBI signals (indicating separate Red, Green, and Blue signals with an Intensity bit). CGA compatibility was hit or miss. There were only three non Tandy monitors that worked with the Tandy 2000 graphics card, all of which are long out of production. These were the original (1986–88) Mitsubishi Diamond Scan, and the NEC Multisync and Multisync GS (grayscale). The required horizontal scan frequency for the Tandy 2000 is 26.4 kHz. Modern flat panel multisync computer monitors cannot sync at frequencies below 30 kHz. The CM 1 monitor is also digital RGB; all modern CRT monitors are analog only.

The Tandy 2000 used quad density 5.25" floppy disks formatted at 720k. This format (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. 1.2 MB 5.25" drives (introduced on the IBM AT) could read quad density disks because they were 80 track and had thinner heads. Various utility programs for DOS existed that could read nonstandard formats such as the Tandy 2000's disks. Much like 1.2 MB 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 read and format 40 track disks in the 2000s 80 track drives, and were readable in drives on ordinary PCs. The floppy controller on the Tandy 2000 is compatible with 3.5" double density 720 KB floppy drives. As of May 2019, there is an abandonware site (winworldpc. 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" disk drive (80 track) to create a system disk bootable in the Tandy 2000 5.25" drive. 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 if its 5.25" boot drive has been replaced with a double density 720 KB 3.5 inch PC drive.

The keyboard was a new design made 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 side of the keyboard in two columns of five. Tandy was among 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 using this arrangement for the Model M keyboard.

The serial port hardware was completely different from the PC/XT's. PC compatible terminal emulation software had to either access the serial hardware strictly through BIOS or use a FOSSIL driver, a software wrapper that virtualized the serial hardware (see also DEC Rainbow), to run on a wider variety of hardware. Several terminal programs were available for the Tandy 2000, making it possible to log in on BBSes, e mail, and other remote systems.

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 third 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 on IBM PCs where the BIOS portion of the OS resided in ROM. The complete MS DOS system (BIOS and BDOS) occupied about 53 KB of RAM. 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.

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, 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). Better BASIC for both the Tandy 2000 and the PC was used to write BBS software for the Tandy 2000 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 Tandy 2000 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 T2000's special features would be operative (except for increased speed and storage). 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 and XT with 360 KB floppy disks. In order to store the largest worksheets, a PC user would have to split them and save them on two disks—and then recombine them in memory later. Although the XT had a hard drive that could store large Lotus worksheets in a single file, a user could not rely on a single storage device for permanent storage of important data files; again they would be forced to segment worksheets for storage on separate disks. The Tandy 2000's large capacity floppy disks made backup maintenance relatively effortless.

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.