At 26th April of 1983, the 'TRS-80 Model 4 Computer' was released.
The TRS‑80 Model 4, introduced on April 26, 1983, was the continuation of the TRS‑80 computer line that had begun with the Model I in 1977 and sold by Tandy Corporation through their Radio Shack stores. The Model 4 was 100% compatible with the Model III and was able to run all Model III operating systems and applications. The designers of the Model 4 had taken great pains to ensure this complete compatibility to avoid the same kind of problems encountered when the TRS‑80 Model III was introduced.
The Model III had been only partially compatible with Model I software and lack of compatibility was viewed as a costly misstep by Radio Shack. Don White, the Model 4 product line manager, stated, “I took it once on the Model I/III incompatibility and I won’t go through that again.”
The Model 4 originally retailed at around $1999.00 but the price was later dropped to around $999.00 and seven years after its introduction it was being blown out at around $600.00. The earliest versions of the TRS-80 Model 4 had a black and white display which later changed to green. Also, the early run of the Model 4 had a non-gate array which was changed to a gate array in later production. The early version had the up/down and left/right keys on opposite sides of the keyboard. The later version clustered the arrow keys together on the right side.
The TRS-80 Model 4 came with either 64k or 128k ram and had either one or two 5.25" floppy drives of 184 KB each. A later Model 4D, or DeskMate, had double sided 384 KB drives. A graphics adapter that came with BASICG was also available for the Model 4. The Model 4 was also originally designed to use the 16-bit Z800 microprocessor from Zilog.
The Z800 was planned by Zilog to be Z80 compatible, yet capable of running new 16-bit software. That would have provided an ideal upgrade path for the Model 4’s future, but unfortunately Zilog never produced the part. Early versions of the Model 4 included a Z800 socket on the motherboard but the socket was removed in later redesigns.
Unlike the versions of TRSDOS for the Model I and III, Radio Shack contracted with an outside company to write the Model 4 operating system. Logical Systems (the authors of LDOS) created TRSDOS 6, regarded as one of the best features of the Model 4. TRSDOS 6 was a very powerful operating system, supporting advanced features such as device redirection, batch processing, and device filtering. It retained most of the commands and feel of Model I TRSDOS, yet added new features to use the improved hardware. Logical Systems also sold TRSDOS 6 under the name LS‑DOS, and it was well known under that name.
The Model 4 could run all Model III software and that feature became unexpectedly important. Internal conflicts within Radio Shack had led to many of the Model 4 software projects in development being cancelled before its release. Although some of those projects were restarted, the delay meant there wasn’t much Model 4 software for months after it was introduced. The delay probably helped to create a stronger third party Model 4 software market. Even with software availability problems, the Model 4 remained Radio Shack’s best selling computer until 1986.
Radio Shack introduced the Model 4P, a transportable Model 4, in 1984. The Model 4P was software compatible with the desktop Model 4, but could be transported in its own carrying case. The final member of the Model I/III/4 line, the Model 4D, was released in 1985. It came standard with double sided drives and was bundled with DeskMate integrated software. Although no longer the focus of Radio Shack’s computer lineup, the Model 4D was available until around 1994, outlasting almost all of the TRS‑80’s original competitors.
Many current computer professionals grew up using a TRS-80 Model 4. Hours spent playing games such as Zaxxon, Frogger and Computer Diplomacy along with programming in BASIC led to lucrative future careers in the computing fields. For that reason the TRS-80 Model 4 is very collectable as many want to relive their younger days and enjoyable times on the Model 4. Quite a few of these machines were made so they are not that hard to find. In really good working condition they can be found for $150.00 to $300.00.
- UniBoInformatica, 2001 - 2007
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