TRS-80 Model 4

Last updated
TRS-80 Model 4
TRS-80 Model 4 (modified).jpg
Manufacturer Tandy Corporation
Type Home and small business computer
Release dateApril 26, 1983;41 years ago (1983-04-26)
Introductory price$1999 (64K, 2 floppy drives, RS-232C), $1699 (64K, 1 floppy drive, no RS-232C) [1]
DiscontinuedLate 1991 (Late 1991) [2]
Operating system TRSDOS 6.2, [3] LS-DOS 6.3 [4] , TRSDOS 1.3, LDOS 5.3, CP/M 2.2 or 3.0
CPU Zilog Z80A @ 4  MHz, 6+ MHz with Z80B / Z80H, or HD64180 / Z180
Memory64  KB or 128 KB, 1 MB plus with third-party upgrades
DisplayModel 4 mode: 24 rows, 80 or 40 columns, Model III mode: 16 rows, 64 or 32 columns, block graphics
Graphicsoptional 640 by 240 pixels for $249 extra
Soundbeeper
Backward
compatibility 		TRS-80 Model III
Predecessor TRS-80 Model III
Successornone

The TRS-80 Model 4 is the last Z80-based home computer family by Radio Shack, sold from April 1983 through late 1991.

Contents

Model 4

TRS-80 Model 4, 1983 non-gate array version TRS-80 Model 4 (modified).jpg
TRS-80 Model 4, 1983 non-gate array version

Tandy Corporation introduced the TRS-80 Model 4 on April 26, 1983 as the successor to the TRS-80 Model III. The Model 4 has a faster Z80A 4 MHz CPU, [5] larger video display of 80 columns by 24 rows, bigger keyboard, and can be upgraded to 128KB of RAM. It is compatible with Model III software and CP/M application software. The Model 4 was announced in the same April 1983 press release as was the TRS-80 Model 100 laptop. The two computers were often marketed by Tandy/Radio Shack as a complementary pair.

A diskless Model 4 with 16KB RAM cost $999; with 64KB RAM and one single-sided 180K disk drive it cost $1699; with 64KB RAM and two drives it cost $1999. An upgrade for Model III owners cost $799 and provided a new motherboard and keyboard. [6]

The Model 4's first appearance in the Radio Shack catalog stated: "Yes, it looks like a Model III, but it's much much more. Compare the price and features of our amazing new Model 4 to any other computer in its class. You'll find that for power, versatility, and convenience it is a true breakthrough. To add the same features to other computers, you'd have to pay a whole lot more." [7] Commenting on its unexpected longevity as a Radio Shack product and object of aftermarket support by third-party companies, in May 1987 80 Micro magazine remarked, "Even when it was introduced in 1983, the Model 4 was seen as a last gasp for the TRS-80 line." [8]

Overview

The computer has the same all-in-one cabinet as the Model III, adopting a more contemporary-looking beige color scheme instead of the black and gray used on the Models I/III. The Model 4 uses WD1770/1773 floppy controllers instead of the WD1791, which allows for a larger gap between the index hole and first sector; later releases of TRSDOS and LDOS were modified for compatibility with the controller.

The Model 4 shipped with TRSDOS 6, identical to Logical Systems's LDOS 6.00 third-party operating system (itself an enhancement to older versions of TRSDOS). When the Model 4 boots into TRSDOS 6, the video display switches into 80×24 mode and the entire 64KB address space is mapped as RAM.

Misosys Inc. sold a Model 4 Hardware Interface Kit which enables the extra keys on the Model 4 keyboard, and in a 128 KB Model 4, the banked memory. [9] Intellitech sold a program called Supermod4 that allows Model III programs running on a Model 4 to activate the 4 megahertz CPU clock, larger video display, the speaker and the function keys. [10] In August 1985 80 Micro magazine published a DoubleDuty-like task switching program that activates the external RAM banks on a 128 KB Model 4 from within Model III mode. [11]

The Model 4 can run CP/M without modification, unlike the Model I and III. [6] [12] Digital Research produced a version of CP/M 3.0 for the Model 4. [13] Montezuma Micro sold a version of CP/M 2.2 that was customized for the Model 4's hardware: banked RAM, reverse video and assignable codes for the function keys. [14] It has a utility for reading and writing CP/M disk formats of many other brands of computer. Montezuma sold a terminate-stay-resident program they called Monte's Window, which provides functionality similar to Borland Sidekick. Its code resided entirely in the banked RAM of a 128K Model 4; no user memory was occupied. [15]

DoubleDuty was made only for the Model 4, marketed by Radio Shack. [16] [17] [18] [19] [20] This is one of the first task-switching programs available for a microcomputer. It uses the upper 64KB of a 128KB machine to keep resident a second TRSDOS application, which can be switched instantly with another application loaded into the main 64KB. A third partition is available for TRSDOS library commands, such as DIR. DoubleDuty first appeared in Radio Shack's 1985 Computer Catalog (RSC-12), the same year that IBM's Topview, Apple's Switcher, and Quarterdeck's DESQview first became available. DoubleDuty was written by Randy Cook, the author of the first version of TRSDOS for the original Model I.

Early versions of the Model 4 mainboard were designed to accept a Zilog Z800 16 bit CPU upgrade board to replace the Z80 8 bit CPU but this option was never released. In 1987 H.I. Tech produced an enhanced CPU board, the XLR8er, [21] using the Hitachi HD64180 Z80-compatible processor.

Reception

Tandy sold 71,000 Model 4 computers in 1984. [22] BYTE in October 1983 noted the lack of native software, but praised the Model 4's backwards compatibility and TRSDOS 6's new features. The magazine concluded that the Model 4 "provides a lot of flexible computing power ... Radio Shack has a guaranteed winner". [6] Creative Computing chose the Model 4 as the best desktop computer under $2000 for 1984, stating that the $1299 price for a system with two disk drives was "a real bargain". [23]

Gate Array Model 4

The original version of the Model 4 (Radio Shack catalog number 26-1069) does not use gate array logic chips on its CPU board, but rather Programmable Array Logic chips (PALs). Starting from late 1984, a revised version was produced which came to be known as the Gate Array Model 4 (catalog number 26-1069A). This change greatly reduced the chip count and allows the circuitry for the Floppy Disk Controller and the RS-232 serial port to be included on the CPU board, making this new Model 4 a single-board computer, unlike the original 26-1069. [24]

The Gate Array version 26-1069A can be distinguished from the older version by its green CRT screen (with greater contrast than the black-and-white CRT) and its four arrow keys grouped in a single cluster (the older version had two arrow keys on each side of its keyboard). The RS-232C serial port of the Gate Array version has its DB-25 connector pointing out the back of the computer's cabinet rather than down at the surface the computer is resting on, which made connection of a serial cable much easier. A Gate Array machine can be upgraded to 128 KB of RAM with industry standard 4161 DRAM chips, not requiring a special PAL chip available only from Radio Shack. The new version runs its Z80 processor at a true clock rate of 4 MHz without wait states, which gave the older version an effective clock rate of about 3.5 MHz.

Model 4P

TRS-80 Model 4P TRS-80 Model 4P Crop Delsener.jpg
TRS-80 Model 4P

The Model 4P (September 1983, Radio Shack catalog number 26-1080) is a self-contained luggable unit. It has all the features of the desktop Model 4 except for the ability to add two outboard floppy disk drives and the interface for cassette tape storage (audio sent to the cassette port in Model III mode goes to the internal speaker). It was sold with the two internal single-sided 180 KB drives. It was later made with the Gate Array technology (catalog number 26-1080A). 80 Micro published an article describing a simple motherboard modification to enable the installation of two external floppy drives. [25]

The 4P's video monitor is 9" compared to the Model 4's 12". The smaller size, and sharper dots, produce better video output. The computer is compatible with popular internal Model 4 peripherals, [26] and has a slot for an internal modem board. The Radio Shack modem uses its own proprietary command set and only supports communications at 300 baud. Teletrends produced a 1200 baud that uses the Hayes command set.

Tandy discontinued the 4P by early 1985, stating that "even though you won't find a more enthusiastic and devoted group of owners than our Model 4P folks, transportables just weren't moving well for any company that also sold a desktop version." [27]

Reception

InfoWorld in 1983 predicted that the 4P would be a "smashing success" as a "substantial improvement" on the Model 4's video and keyboard. The magazine said that it was "truly a transportable computer" and approved of the "carefully thought-out mechanical design", not too large or small. Although criticizing the computer's lack of advanced documentation or double-sided drives, InfoWorld concluded that the 4P "is an outstanding product at an excellent price". [26]

Model 4D

The final version of the Model 4 is the Model 4D (Radio Shack catalog number 26-1070), first sold in 1985. It is a Gate Array desktop machine featuring dual TEC FB-503 disk drives [28] with a capacity of 360KB each (double density sectors, 40 track, double-sided). Rather than using a lever-style latch as had previous Model 4 drives, these drives use a twist-style latch that provides for more reliable clamping. They are half-height drives mounted with full-height faceplates.

The DeskMate productivity suite is bundled with the 4D. It supplies simple applications including a word processor, filer, spreadsheet, calendar, and mail manager.

Later Misosys, Inc. updated LS-DOS 6.3 to support dates through December 31, 2011 (as well as a few other enhancements). The Model III LDOS 5.1.4 was also updated to version 5.3, supporting the same feature set as LS-DOS 6.3. [29]

The Model 4D is the last computer descended from Radio Shack's original Model I from 1977 but it is not branded as a Radio Shack product. The badge mounted on its front cover brands it as the "Tandy TRS-80 Model 4D". This change in marketing resulted from Tandy corporation's desire to enhance its stature in the marketplace, because it was perceived by some in the computer press that the old "Radio Shack" moniker connoted an image of inferior quality. The Model 4D is the last computer to bear the "TRS-80" name. It retailed for $1199 at its introduction in 1985. During 1987–1988 the retail stores removed the Model 4Ds from display but they were kept in the yearly computer catalog and were available by special order through 1991, [30] when they were closed out for $599. Parts and repair service remained available for several years longer.

Related Research Articles

<span class="mw-page-title-main">TRS-80</span> 1977 microcomputer by Tandy Corporation

The TRS-80 Micro Computer System is a desktop microcomputer launched in 1977 and sold by Tandy Corporation through their Radio Shack stores. The name is an abbreviation of Tandy Radio Shack, Z80 [microprocessor]. It is one of the earliest mass-produced and mass-marketed retail home computers.

<span class="mw-page-title-main">TRS-80 Color Computer</span> Line of home computers

The RadioShack TRS-80 Color Computer, later marketed as the Tandy Color Computer, is a series of home computers developed and sold by Tandy Corporation. Despite sharing a name with the earlier TRS-80, the Color Computer is a completely different system and a radical departure in design based on the Motorola 6809E processor rather than the Zilog Z80 of earlier models.

<span class="mw-page-title-main">Tandy 1000</span> IBM PC compatible home computer system

The Tandy 1000 is the first in a line of IBM PC compatible home computer systems produced by the Tandy Corporation for sale in its Radio Shack and Radio Shack Computer Center chains of stores. Introduced in 1984, the product line was aimed at providing affordable but capable systems for home computing or education, with some of its Tandy specific features like graphics, sound and joystick port making it more appealing for home use.

Microsoft BASIC is the foundation software product of the Microsoft company and evolved into a line of BASIC interpreters and compiler(s) adapted for many different microcomputers. It first appeared in 1975 as Altair BASIC, which was the first version of BASIC published by Microsoft as well as the first high-level programming language available for the Altair 8800 microcomputer.

<span class="mw-page-title-main">Tandy 2000</span> 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 used the older 4.77 MHz Intel 8088 processor, and the IBM PC/AT 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. 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.

<span class="mw-page-title-main">TRSDOS</span> Operating system for Tandy TRS-80 computers

TRSDOS is the operating system for the Tandy TRS-80 line of eight-bit Zilog Z80 microcomputers that were sold through Radio Shack from 1977 through 1991. Tandy's manuals recommended that it be pronounced triss-doss. TRSDOS should not be confused with Tandy DOS, a version of MS-DOS licensed from Microsoft for Tandy's x86 line of personal computers (PCs).

<span class="mw-page-title-main">TRS-80 MC-10</span>

The TRS-80 MC-10 microcomputer is a lesser-known member of the TRS-80 line of home computers, produced by Tandy Corporation in the early 1980s and sold through their RadioShack chain of electronics stores. It was a low-cost alternative to Tandy's own TRS-80 Color Computer to compete with entry-level machines such as the VIC-20 and Sinclair ZX81.

<span class="mw-page-title-main">Tandy Pocket Computer</span> Line of pocket computers

The Tandy Pocket Computer or TRS-80 Pocket Computer is a line of pocket computers sold by Tandy Corporation under the Tandy or Radio Shack TRS-80 brands.

<span class="mw-page-title-main">TRS-80 Model 100</span> Portable computer introduced in 1983

The TRS-80 Model 100 is a notebook-sized portable computer introduced in April 1983. It was the first commercially successful notebook computer, as well as one of the first notebook computers ever released. It features a keyboard and liquid-crystal display, in a battery-powered package roughly the size and shape of a notepad or large book. The 224-page, spiral-bound User Manual is nearly the same size as the computer itself.

<span class="mw-page-title-main">Video Genie</span> Series of computers produced by Hong Kong-based manufacturer EACA during the early 1980s

Video Genie is a discontinued series of computers produced by Hong Kong-based manufacturer EACA during the early 1980s. Computers from the Video Genie line are mostly compatible with the Tandy TRS-80 Model I computers and can be considered a clone, although there are hardware and software differences.

<span class="mw-page-title-main">Scripsit</span>

Scripsit is a word processing application written for the Radio Shack TRS-80 line of computers. Versions were available for most if not all computers sold under the TRS-80 name, including the TRS-80 Color Computer and several pocket computer designs, as well as the Tandy version of the Xenix operating system. Tandy Corp. also produced a version running under MS-DOS for its line of PC compatible computers. Some of the 8-bit versions are tape-based and have no ability to read or write to disk.

<i>80 Micro</i> Computer magazine published between 1980 and 1988

80 Micro was a computer magazine, published between 1980 and 1988, that featured program listings, products and reviews for the TRS-80.

The Tandy 10 Business Computer System was a short-lived product developed by Radio Shack in the late 1970s as a business-oriented complement to their TRS-80 Model I desktop computer. Released in 1978, the Tandy 10 was built for Radio Shack by Applied Digital Data Systems (ADDS), and was only sold by Radio Shack's dedicated computer center stores.

NewDos/80 is a third-party operating system for the Radio Shack TRS-80 line of microcomputers released in 1980. NewDos/80 was developed by Apparat, Inc., of Denver, Colorado. NewDos/80 version 2.0 was released in August 1981. It ran on the TRS-80 Model I and Model III.

<span class="mw-page-title-main">TRS-80 Model II</span> Tandy Radio Shack small-business computer launched in 1979

The TRS-80 Model II is a computer system launched by Tandy in October 1979, and targeted at the small-business market. It is not an upgrade of the original TRS-80 Model I, but a new system.

<span class="mw-page-title-main">Home computer</span> Class of microcomputers

Home computers were a class of microcomputers that entered the market in 1977 and became common during the 1980s. They were marketed to consumers as affordable and accessible computers that, for the first time, were intended for the use of a single, non-technical user. These computers were a distinct market segment that typically cost much less than business, scientific, or engineering-oriented computers of the time, such as those running CP/M or the IBM PC, and were generally less powerful in terms of memory and expandability. However, a home computer often had better graphics and sound than contemporary business computers. Their most common uses were word processing, playing video games, and programming.

The MAX-80 is a personal computer released in 1982 by Lobo Systems. It differed from other TRS-80 compatible computers in that it was not hardware compatible with the TRS-80.

The Tandy 3000 is a personal computer introduced by Radio Shack in 1986 based on the 16-bit 8 MHz Intel 80286 microprocessor.

Apparat, Inc., was an American software developer, peripheral manufacturer, mail order company, and retailer active from 1978 to 1988 and primarily based in Denver, Colorado. They are best known for NewDos/80, an alternative operating system to TRSDOS for Tandy Corporation's TRS-80 line of home computers, sold through their Radio Shack stores. Apparat themselves sold modified TRS-80s through their mail order catalog. The company pivoted to selling peripherals for the IBM Personal Computer in 1982, continuing in this market until Apparat went defunct in 1988.

References

  1. ↑ "1984 Radio Shack Computer Catalog RSC-10 page 18". radioshackcatalogs dot com. Tandy/Radio Shack. 1984. Retrieved November 25, 2022.
  2. ↑ "1990 Radio Shack Computer Catalog RSC-21 page 34 (effective thru fall 1991)". radioshackcatalogs dot com. Tandy/Radio Shack. 1990. Retrieved November 25, 2022.
  3. ↑ "1985 Radio Shack Computer Catalog RSC-12 page 28". radioshackcatalogs dot com. Tandy/Radio Shack. 1985. Retrieved November 25, 2022.
  4. ↑ "LSI Delivers". 80 Micro (Advert). May 1987. p. 10. Retrieved October 22, 2019.
  5. ↑ Goldklang, Ira (March 4, 2009). "TRS-80 Computers: TRS-80 Model 4". Ira Goldklang's TRS-80 Revived Site. Retrieved 2019-05-19.
  6. 1 2 3 Archer, Rowland Jr. (October 1983). "Radio Shack's TRS-80 Model 4". BYTE . Vol. 8, no. 10. pp. 292–302. Retrieved January 31, 2015.
  7. ↑ "Radio Shack Computer Catalog CCF-836, page 9". Radio Shack Catalogs dot com. Tandy/RadioShack. 1983. Retrieved November 25, 2022.
  8. ↑ Essex, David (May 1987). "TRSDOS's Bittersweet Reality". 80 Micro . p. 19. Retrieved October 22, 2019– via Internet Archive.
  9. ↑ Soltoff, Roy (Winter 1987). "LDOS 5.3 Model 4 Hardware Interface Kit" (PDF). The Misosys Quarterly. Vol. I, no. iii. Misosys, Inc. p. 6. Retrieved November 6, 2019– via tim-mann dot org.
  10. ↑ Dalton, David (September 1985). "The Enhancer". 80 Micro. CW Communications. p. 33. Retrieved November 5, 2019.
  11. ↑ Snyder, E. Cameron (August 1985). "The Great Divide". 80 Micro . CW Communications. p. 63. Retrieved November 5, 2019.
  12. ↑ Goldklang, Ira. "TRS-80 – CP/M". Ira Goldklang's TRS-80 Revived Site. Retrieved 2019-05-19.
  13. ↑ "1985 Radio Shack Computer Catalog pg. 28". Radio Shack Catalogs. Avnet Electronic Components. 1985. Retrieved October 25, 2016.
  14. ↑ Harrell, John B. (March 1985). "CP/M 2.2 Revisited". 80 Micro . CW Communications. p. 35. Retrieved July 9, 2020.
  15. ↑ Harrell, John B. (August 1985). "A Window on the CP/M World". 80 Micro . CW Communications. p. 36.
  16. ↑ "First appearance of DDuty in RS Computer Catalog RSC-12 page 27, 1985". Radio Shack Catalogs dot com. Tandy/Radio Shack. Retrieved December 2, 2022.
  17. ↑ Ludwig, Gary A. (October 1985). "Concurrent Events with DoubleDuty". 80 Micro . CW Communications. p. 36. Retrieved July 9, 2020.
  18. ↑ Soltoff, Roy. "DoubleDuty 2.6.0 Released" (PDF). The Misosys Quarterly. Misosys, Inc. Retrieved July 17, 2020– via www.tim-mann dot org.
  19. ↑ Sherman, Lynn R. "CTL255/FLT" (PDF). The Misosys Quarterly. Roy Soltoff, Misosys, Inc. p. 40. Retrieved July 17, 2020– via www.tim-mann dot org.
  20. ↑ Davis-Wright, Ryan (November 1985). "PRO-NTO: TRSDOS 6.x's Sidekick". 80 Micro. CW Communications. p. 29. Retrieved July 9, 2020.
  21. ↑ Potter, William H. (August 1987). "4 In the Fast Lane". 80 Micro. CW Communications. p. 38. Retrieved July 9, 2020.
  22. ↑ Bartimo, Jim (March 11, 1985). "Tandy Revamps Product Line". InfoWorld . Vol. 7, no. 10. pp. 28–29. Retrieved January 21, 2015.
  23. ↑ Ahl, David H. (December 1984). "Top 12 Computers of 1984". Creative Computing . 10 (12): 14, 16. ISSN   0097-8140 . Retrieved April 27, 2023– via Internet Archive.
  24. ↑ "TRS-80 Home Page, The Model 4 "info in Model 4 section pertains to Gate Array changes"". classiccmp dot org. Pete Cervasio. Retrieved May 8, 2019.
  25. ↑ Tam, Tsun (Spring 1990). "Upgrade Your 4P with External Floppy Drives" (PDF). The Misosys Quarterly. Vol. IV, no. iii. 80 Micro (reprinted by Roy Soltoff/Misosys Inc.). p. 27. Retrieved May 14, 2019– via tim-mann dot org.
  26. 1 2 Daneliuk, Tim (1983-11-21). "Review: Radio Shack TRS-80 Model 4P". InfoWorld . Vol. 5, no. 47. pp. 82–83. Retrieved 2020-04-13.
  27. ↑ Juge, Ed (October 1985). "News for the top: what's really going on at Tandy". Creative Computing. p. 108. Retrieved 14 October 2016.
  28. ↑ Tooley, Michael (1988). Servicing Personal Computers. Heinemann Professional Publishing. p. 146, table 4.3. ISBN   978-1-4831-0103-3.
  29. ↑ Soltoff, Roy (Fall 1986). "LDOS 5.3.0 Upgrade Kit" (PDF). Misosys Quarterly. Vol. I, no. ii. Misosys, Inc. p. 13. Retrieved February 18, 2020– via tim-mann dot org.
  30. ↑ "1990 Radio Shack Computer Catalog RSC-21 page 34 (effective thru fall 1991)". radioshackcatalogs dot com. Tandy/Radio Shack. 1990. Retrieved November 26, 2022.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.