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---
title: Tandy Radio Shack TRS 80 MODEL 4
categories:
- Computers
types:
- Professional Computer
origins:
- U.S.A.
years:
- '1983'
cpus:
- Zilog Z80
params:
name: TRS 80 MODEL 4
image: /media/museum/photos/tandy_model4_running_s1.jpg
company: /companies/tandy-radio-shack
company_name: Tandy Radio Shack
specs:
- label: NAME
value: TRS 80 MODEL 4
- label: MANUFACTURER
value: Tandy Radio Shack
- label: TYPE
value: Professional Computer
- label: ORIGIN
value: U.S.A.
- label: YEAR
value: '1983'
- label: BUILT IN LANGUAGE
value: None
- label: KEYBOARD
value: Typewriter style 83 keys with numeric keypad
- label: CPU
value: Zilog Z80
- label: SPEED
value: 4 MHz
- label: RAM
value: 64 KB (up to 128 KB)
- label: ROM
value: 14 KB
- label: TEXT MODES
value: 64 x 16 / 32 x 16 / 64 x 40 / 80 x 24
- label: GRAPHIC MODES
value: None
- label: COLORS
value: Monochrome green phosphore
- label: SOUND
value: Built-in speaker
- label: SIZE / WEIGHT
value: 47.5 (W) x 52 (D) x 31 (H) cm
- label: I/O PORTS
value: Tape (500 or 1500 bauds), Centronics, I/O ports compatible with Model III, Serial (4D)
- label: BUILT IN MEDIA
value: One or Two 5.25'' disk-drives
- label: OS
value: TRSDOS 6.0 or 1.3, LDOS, CP/M
- label: POWER SUPPLY
value: Built-in power supply unit
- label: PRICE
value: |-
From $1990. In later years the price came down to about $1000\
By 1990 the Model 4D was being closed out at $599
tabs:
- photos
- adverts
- hardware
- emulators
- links
photos:
- title: FIRST VERSION
subtitle: ''
text: Two Model 4 versions were released. One can recognize them at the surface from the different arrangement of the arrow keys.
image: /media/museum/photos/tandy_model4_system_s1.jpg
- title: SECOND VERSION
subtitle: ''
text: |-
The second version had an improved gate-array mainboard and a new location for the serial port.\
The arrow keys are now clustered to the right of the keyboard.\
This version features a second 3.5" DS DD 720 KB floppy drive (Tandy option).
image: /media/museum/photos/tandy_model4_systemus_s1.jpg
- title: MODEL 4 PLATE
subtitle: ''
text: ''
image: /media/museum/photos/tandy_model4_plate_s1.jpg
- title: BOTH KEYBOARD VERSIONS
subtitle: ''
text: ''
image: /media/museum/photos/tandy_model4_keyboards_s1.jpg
- title: KEYBOARD CLOSE-UP
subtitle: ''
text: The red button is the Reset switch
image: /media/museum/photos/tandy_model4_keybcloseup_s1.jpg
- title: SIDE VIEW
subtitle: ''
text: ''
image: /media/museum/photos/tandy_model4_sideview_s1.jpg
- title: TOP VIEW
subtitle: ''
text: ''
image: /media/museum/photos/tandy_model4_topview_s1.jpg
- title: FRONT PANEL
subtitle: ''
text: Both FDD drives were Tandon Single-sided, single density models.
image: /media/museum/photos/tandy_model4_fdds_s1.jpg
- title: BOTTOM SIDE
subtitle: ''
text: |-
**(1)** Parallel printer connector\
**(2)** Serial connector\
**(3)** Expansion port connector\
**(4)** Video adjustment\
**(5)** Tape recorder DIN socket
image: /media/museum/photos/tandy_model4_bottomview_s1.jpg
- title: 'INSIDE #1'
subtitle: ''
text: The mainboard is mounted vertically at the back.
image: /media/museum/photos/tandy_model4_inside_s1.jpg
- title: 'INSIDE #2'
subtitle: ''
text: The top cover holds the CRT and its electronics. A fan has been added on top of the CRT.
image: /media/museum/photos/tandy_model4_topcover_s1.jpg
- title: MAINBOARD, 1ST VERSION
subtitle: ''
text: |-
The fist mainboard version used only standard chips. It had 64 KB of RAM. Provision was made for a second 64 KB RAM bank.\
The separate floppy-disk controller card was located behind the mainboard as well as a smal sound generator circuit.
image: /media/museum/photos/tandy_model4_mainboard_s2.jpg
- title: MAINBOARD, 2ND VERSION
subtitle: ''
text: |-
The second "gate array" version included the floppy-disk controller, the sound generator and buzzer and a second serial port.
**(1)** Power connector\
**(2)** Video connector\
**(3)** Tape recorder connector\
**(4)** 128 KB RAM chips (16x4164 equivalents)\
**(5)** WDC1865 UART, serial port controller\
**(6)** WD1773 floppy-disk controller\
**(7)** BIOS ROMs\
**(8)** Z80 CPU socket. In this machine, the CPU chip was replaced by a RAM expansion piggy-back card
Other chips were custom made for Tandy and had unknown part numbers.
image: /media/museum/photos/tandy_model4_mainboard_s1.jpg
- title: RAM CARD
subtitle: ''
text: This RAM card is inserted on the Z80 CPU socket and provides up to 1 MB of extra RAM (2 x 512 KB DIP modules) used as a virtual floppy-disk drive.
image: /media/museum/photos/tandy_model4_ramcard_s1.jpg
adverts:
- title: US ADVERT, NOV. 1985
subtitle: ''
text: ''
image: /media/museum/pubs/tandy_model4d_pub_s1.jpg
hardware:
- title: REMOTE UNIT ACTIVE
subtitle: Serial# 26-1210
text: |-
This rare unit is meant for teachers to control up to 16 TRS-80 Model 1 from a another TRS-80 equiped with min-disk. All the controled TRS-80 model 1 must be equiped with Level II.
It cost 2895fr (France, 1981)
image: /media/museum/hardware/tandy_trs80-m1_remote-unit-active.jpg
- title: NETWORK II BOX
subtitle: p/n 26-1211
text: |-
This box allowed up to 16 TRS computer to be networked. Three network boxes were released by Tandy (I, II and III).\
The Network II required verbal communication between the server operator and the remote user, and data transfer had to be completed one user at a time.\
The network III allowed automated control of the network so that users could easily access programs and data stored on the server's storage device.
Thanks to **David Sutherland** for the pictures.
image: /media/museum/hardware/tandy_network2_s1.jpg
- title: DMP-200
subtitle: ''
text: 80-column, 100 cps dot matrix printer.
image: /media/museum/hardware/tandy_model3_dmp200_s1.jpg
- title: DAISY WHEEL PRINTER II
subtitle: Serial# 26-1158
text: |-
This is a high-quality printer meant to be used with wordprocessors. Some interchangeable daisy-wheels were available (Courrier, Elite, Madeleine). It could print 163 characters per line (34cm), at a 43 cps rate.
It cost 9595fr (France, 1981)
image: /media/museum/hardware/tandy_trs80-m1_daisy-wheel-printer-2_1.jpg
- title: LINE PRINTER I
subtitle: Ref# 26-7017
text: |-
This printer was a custom version of the Oki Microline 80.\
Printed lower and upper case on paper rolls or listing paper (24cm wide) from 40 to 80 columns/line, at a speed rate of 28 lines/minute.
It cost 716 Euros in 1981 (France).
image: /media/museum/hardware/tandy_model1_lineprinter1_s1.jpg
- title: LINE PRINTER III
subtitle: Serial# 26-1156
text: This printer can print lower and upper case, at a speed rate of 120 c/s, on paper up to 38cm wide. It is conceived for intensive use ! It cost 9950fr in 1981 (France).
image: /media/museum/hardware/tandy_trs80-m1_line-printer-3_1.jpg
- title: LINE PRINTER VI
subtitle: Serial# 26-1166
text: |-
This large printer can print lower and upper case, graphic characters and symbols at a speed rate of 100 c/s ! This is definately a professional printer.
It cost 5495fr in 1981 (France).
image: /media/museum/hardware/tandy_trs80-m1_line-printer-6_1.jpg
- title: TP-10 THERMAL PRINTER
subtitle: Box
text: ''
image: /media/museum/hardware/tandy_trs80_tp-10_thermal-printer_box.jpg
- title: EXATRON
subtitle: Stringy Floppy drive
text: |-
The Exatron Stringy Floppy (ESF) was a low-cost data—storage system that fitted the gap, between cassettes and disk drives.\
The system was based on a miniature endless—loop tape cartridge called a "wafer".\
The amount of data that could be recorded on a wafer depended on the length of tape in it, typically, a 50—foot wafer could hold at least 40 KB of programs or data.
**Matt** reports to us:\
A curiousity about the model 1, CPU SPEED had a direct relatonship with STORAGE CAPACITY. if you doubled the clock speed of your MODEL 1 CPU you doubled the amount of data you could store on your stringy floppies. this is a feat that no other computer no matter how many ghz you have in your PC can do today without using compression.
Thanks to **David Sutherland** for the pictures
image: /media/museum/hardware/tandy_model3_exatronwafer_s1.jpg
emulators:
- title: David Keil's TRS-80 Model III/4/4P Emulator Page
url: http://discover-net.net/~dmkeil/trs80/model4.htm
platform: MS DOS
text: This program emulates a complete TRS-80
- title: Matthew Reed's TRS-80 Emulator Web Site
url: http://www.arrowweb.com/mkr/
platform: MS DOS
text: This page offers shareware versions of a TRS-80 Model 4 emulator and a TRS-80 Model 1-2 emulator
- title: TRS-80 Model III/4 Emulator
url: http://www.vavasour.ca/jeff/trs80.html#model4
platform: MS DOS
text: This TRS-80 Model III/4 Emulator is a commercial product
- title: Model 4 Emulator
url: http://www.arrowweb.com/mkr/
platform: Windows
text: ''
- title: XTRS for Unix / X
url: http://www.research.digital.com/SRC/personal/Tim_Mann/trs80.html
platform: Unix / Linux
text: ''
- title: 'xtrs: TRS-80 Model I/III/4 Emulator for Unix'
url: http://www.tim-mann.org/xtrs.html
platform: Unix / Linux
text: xtrs is a Radio Shack TRS-80 Model I/III/4/4P emulator for Unix and the X Window System
- title: TRS-80 Level I BASIC in a browser
url: http://www.vavasour.ca/jeff/trs80.html#simulator
platform: Other platform
text: With this Java emulator, you'll be able to write a BASIC program directly in your browser!
- title: Ira Goldklang's TRS-80 Revived Pages
url: http://www.trs-80.com/trs80-e.htm
platform: Multiplatform
text: A complete list of TRS-80 emulators for various platforms !
- title: MESS
url: http://www.mess.org
platform: Multiplatform
text: MESS emulator also emulates a TRS-80 systems
links:
- title: 8bit-micro.com - Online TRS-80 Computer Magazine
url: HTTP://WWW.8BIT-MICRO.COM
text: Online Magazine dedicated to the TRS-80 and other Vintage - Monthly Issues
- title: David's TRS-80 Page
url: http://freespace.virgin.net/david.sampson/
text: ''
- title: Ira Goldklang's TRS-80 Revived Pages
url: http://www.trs-80.com/
text: Lof of infos about all TRS-80 computers
- title: Java TRS-80 Model 1 BASIC Interpreter
url: http://ganley.org/software/trs80.html
text: ''
- title: Mike's Personal Computer Museum
url: http://personal.nbnet.nb.ca/mclays/trsmod1.html
text: Level 1 & 2 Basic summaries, Tandy time-lines, price-list, etc ... !
- title: RadioShackCatalogs.com
url: http://www.RadioShackCatalogs.com
text: Here, you can actually/virtually flip-through the pages to view the content of every RadioShack catalog!
- title: The TRS-80 Home Page
url: http://www.kjsl.com/trs80
text: Full of infos
- title: Tim Mann's TRS-80 Page
url: http://www.tim-mann.org/trs80.html
text: Infos, tools and home of xtrs, a Model I/III/4 emulator for Unix
- title: Web Wiz CAPTCHA
url: http://www.webwizcaptcha.com
text: Discussion about Tandy computers
comments:
- author: Jay (Washington State USA)
date: Tuesday 22nd September 2020
text: |-
I am looking for one of these at a cheap price, I will pay up to 100$ including shipping if I have to pay for it\
Email is jaya.buckwheat@gmail.com
- author: David Coffey (Florida, United States)
date: Friday 11th September 2015
text: To Jeffrey Joseph who posted a nice response. I, too, had a gate-array with the split arrow keyboard. Why? I had purchased the Model 4 and discovered it had a different keyboard than the Model 4 I already owned (non-gate). At the time I was not knowledgeable between the gate and non-gate systems though I had noticed the printer port was pointing out of the back instead of the bottom. I always played video games on my Model 4s and Model 3s and even the Model 3 had the same split arrow keyboard. On the new gate array, I was dismayed with the new clumped arrow keys and hated it for playing games. i actually found a supplier and bought an old split arrow keyboard and replaced it myself in the gate array. It was very easy. So, that''s how I ended up with the split arrow keyboard on my gate array Model 4.
- author: David Coffey (Florida, United States)
date: Friday 11th September 2015
text: I had several Model 3''s, Model 4''s and one Model 4p. Loved these little systems. The last Model 4 I owned in 1995 I purchased a Zilog Z-80a chip and replaced the Z-80 I had in it. The Z-80a ran at the same 4Mhz but it had the added ability to boot from an external hard disk drive without the need of a floppy. I had a 15MB hard disk drive (MFM) for my Model 4.
- author: Chuck Rose (Vermont/USA)
date: Sunday 1st February 2015
text: |-
It''s not quite accurate to say that double sided drives was the only thing to change in the Model 4D. It would lead you to believe that the ''D'' stood for double sided. In fact the ''D'' stood for "Deskmate" which was a piece of software that worked as a pseudo GUI (keyboard controlled) and also contained some simple productivity software like a text editor, spreadsheet, database, terminal program, scheduler, and an ''email'' program that allowed you to send messages to any other deskmate user via modem.
These were very basic applications without any bells and whistles but was good if you didn''t want to deal with the command line or if you just needed basic productivity software.
- author: Kurt baumgardner (US)
date: Sunday 10th October 2010
text: |-
@Ninfa:
Is the table white, with 2 cutouts, and z-style legs? Any chance you wanted to sell any of it?
- author: Ninfa Carpenter (US)
date: Saturday 25th September 2010
text: |-
We have a TRS-80 full set. This computer belong the\
Previous owner that we purchase the home in1995.\
He became ill and now has passed. We have the table,\
Manuel''s, discs, electrical hook up, key board, tV screen,\
Paper, printer, and great condition. Does any one know some\
one that might save this computer. We Re selling our home\
and do not want to throw away. I read lots of comments and see\
people still show a passion for specialize computer.
- author: Sean (California)
date: Friday 11th June 2010
text: My family had one of these long ago. Some years after my military service ended, I asked about it and found it had been given to my brothers in-laws and had been subsequently thrown away. I remember waiting forever for the word processor to load from the tape drive because we couldn''t afford the floppy disk drives. Radio Shack was really good with everything about these computers and I bought a book that showed me how to convert Apply programs to TRS-80. I spent hours and hours making the fireworks program. In re-living my past, I''ve been considering finding an old TRS-80 model 4 and installing all new components in it, mixing the new with the old. That way I could have a functional antique computer. However, my imagination might just be too ambitious.
- author: Paul Vassiliou (U.S)
date: Saturday 8th May 2010
text: I found one of these in my Grandfathers attic after he passed away. It powers on and still has the original cardboard slips in the floppies. If anyone is interested in it email me at paulvassiliou@live.com
- author: Jeffrey Joseph (Norfolk Virginia)
date: Saturday 17th April 2010
text: |-
Your description and photo of the TRS-80 Model 4 is very interesting:\
First, your photo. You show a green-screen computer with split-arrow keyboard. Perhaps I should explain:\
The Model 4 was produced in two distinct versions (not mentioned in your description). Initially, in April 1983, was the so-called "Non-gate array". This had a black-and-white CRT with a keyboard that had the four arrow keys split between the left- and right-hand sides of the keyboard. The up/down keys on the left, and the right/left keys on the right. This model is also distinct in that it used PAL chips for its digital logic on the PCB. Also, to include the optional peripherals (disk, RS-232), it required the installation of multiple circuit boards within the cabinet. What''s more, to expand to the maximum 128K of RAM, a special expansion PAL chip was required.\
Then came the so-called "gate-array" Model 4 sometime in mid-1984. This model included ALL digital circuitry on one circuit board (including FDC and RS-232) as standard feature. It could be expanded to 128K RAM with no special PAL chip $ only the new RAM need be installed and a shorting block (jumper) moved. The gate-array Model 4 also included a green CRT and a new keyboard which had all four arrow keys grouped in a cluster at the lower-right of the keyboard. Yet another useful feature of the gate-array model was that all connectors were repositioned so that they faced directly out the back of the cabinet, rather than straight downward, as they had on the non-gate-array. (the later Model 4D also had a backspace key, double-sided drives, and included DeskMate integrated application software. In its last years the 4D also came from Tandy with LS-DOS 6.3 operating system with many enhanced features).\
$-The reason your Model 4 photo is so interesting is because you show a Model 4 with a new green screen and the old split-arrow-key keyboard. Perhaps this is a gate-array computer with an old-style keyboard replacement. Then again, when Tandy was transitioning between non-gate-array and gate-array production, a very few computers were shipped with the new CRT and old keyboard because of vendor supply issues. If this is so, you have a very rare specimen on your hands! $-\
Right from the beginning, all Model 4s provided for the optional high-resolution graphics board which endowed the machine with 640 x 240 resolution and 32K of additional port-accessed memory.\
There were many many aftermarket upgrades available from third-party vendors and enthusiastic hackers. The clock rate of the non-gate array could be upped to 6 megahertz, and the gate array could go as far as 7 Mhz. By substituting 256K DRAMs, memory could go up to one megabyte by double-stacking the chips in the Model 4 sockets. Fortunately, the authors of the LS-DOS (TRSDOS 6) operating system made provision in the software for such memory expansion with their ingenious @BANK supervisor call. The expansion memory beyond the Z-80''s 64K limit was accessible as a RAMDISK, or at the same time (user-definable) as distinct 32K banks to applications software (such as PRO-WAM, SuperLog, Said, Allwrite). Later, a company called Hi-Tech made available their XLR8er expansion board which simply plugged into the Z-80 socket, making an easy expansion of 256K and 6.144 Mhz Z-180 (8 Mhz Z-80 equivilant). The XLR8er, since it only used the Z-80 socket, could co-exist with the other megamemory mods that only used the DRAM sockets, and the operating software was easily adaptable because its complete assembler source code was available to the dedicated hacker with publication of LSI''s THE SOURCE.\
In this regard of openness of the machine architecture, I would be remiss not to mention that Tandy alone of almost all computer manufacturers, always made available to the public all of the technical data on its products. For each and every of its computers, anyone could order both the Technical Reference Manual (including schematics and theory of operation), and the Service Manuals (including maintenance and troubleshooting data).\
Indeed, availability of these data made possible the many many hacker upgrades published for the TRS-80 Model 4 in its many incarnations and thus contributed greatly to its beloved and long-lived status among vintage computer enthusiasts.
- author: Alex (Goshen, Indiana )
date: Sunday 22nd January 2006
text: I have a trs-80 with the green screen starting to blur objects together. Everything else works great on it still. Is there any places that sell parts for trs-80s to replace the screen?
- author: Jesse (Washington)
date: Tuesday 28th September 2004
text: I have a TRS-80 printer and I should have the manual somewhere but I cant find it. I was hoping someone would know what the powersupply that is required for it.
- author: Brian K. Hahn (Alberta, Canada)
date: Monday 24th May 2004
text: |-
The support for the TRS-80 is still very much alive. Visit tthe TRS-80 Web at: http://www.ringsurf.com/netring?ring=trs80;action=list
Old-computers.com is a great site and hats off to your accomplishments Sylvain!
- author: Lori (Garland, TX)
date: Saturday 17th May 2003
text: Can anyone tell me what the original price was for a TRS-80?
- author: Dano (Nebraska)
date: Friday 28th March 2003
text: I have a TRS-80 model 4 with many (MANY) books, software(games and business) and the TRS-80 printer. I was wondering what a fair price to sell it would be.
related:
- /museum/radionic-model-r1001
- /museum/sysdata-eletronica-jr
- /museum/tandy-radio-shack-trs-80-model-12
- /museum/tandy-radio-shack-trs-80-model-16
- /museum/tandy-radio-shack-trs-80-model-4p
- /museum/tandy-radio-shack-trs-80-model-i
- /museum/tandy-radio-shack-trs-80-model-ii
- /museum/tandy-radio-shack-trs-80-model-iii
oc_id: 244
source:
url: https://web.archive.org/web/20230608082555/http://www.old-computers.com/museum/computer.asp?c=244
date: '2023-06-08'
---
The TRS-80 model 4 (ref 26-1068/69) was one of the last models of the TRS-80 series (and perhaps the less known). It ran at 4 MHz and displayed 80 columns x 24 lines in Model 4 mode, but was fully compatible with the [TRS-80 model 3](/museum/tandy-radio-shack-trs-80-model-iii/) and in Model 3 mode actually displayed 64x16 and ran at the Model 3's 2 MHz.
It had 64 or 128 KB RAM, the 64 upper KB being used as a ram disk. It had one or two 5.25" floppy disk (184 KB each) and ran under TRSDOS 6.0 or 1.3, LDOS or CP/M.
A transformation kit "TRS80 model III -> model IV" was available.
The Model 4 was followed by the **Model 4D** (ref. 26-1070). The only difference being double sided drives -384 KB, instead of single sided drives.
A portable version of the Model IV called [Model 4P](/museum/tandy-radio-shack-trs-80-model-4p/) (ref. 26-1080) was also marketed few time after.
---
**Dwight Briney** specifies:\
A graphics adapter was also available for the Radio Shack TRS-80 Model IV in 1983. It came with a graphics programming language (BASICG). I used BASICG to program a basketball shot chart program that was used for a few seasons until I finally converted it to the IBM compatible Hercules graphics adaptor that had higher resolution.\
It all seems pretty primitive now, but it worked great at the time.
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