Tandy TRS-80 Model IV

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The TRS-80 was Tandy Corporation's desktop microcomputer model line, sold through Tandy's Radio Shack stores in the late 1970s and early 1980s.

The successor to the Model III was the Model 4 (April 1983, with "4" written as an Arabic numeral), which included the capability to run CP/M.

Running CP/M had previously only been possible via a hardware modification that remapped the BASIC ROMs away from memory address zero, such as the third-party add-on sold as the Omikron Mapper board, or by running a version of CP/M modified to run at a starting address other than zero. However, this also required modified applications, since the area of memory at zero contained the vectors for applications to access CP/M itself. The Model 4 also added an 80 column by 24 line video display mode required for CP/M compatibility.

The Model 4 shipped with TRSDOS 6, an enhanced version of LDOS by Logical Systems and a vastly superior operating system to Tandy's earlier TRSDOS offerings. When the Model 4 booted into TRSDOS 6 the video display switched into 80×24 mode and the entire 64KB address space was mapped as RAM. The Model 4 was also capable of running all Model 3 software when a Model 3 operating system disk was detected and loaded during bootup with a 64×16 video mode and Model 3 ROMs mapped from address zero.

The Model 4 also had the ability to display 640×240 or 512×192 high-resolution monochrome graphics with an optional board. A "luggable" version known as the Model 4P (1983) was a self-contained unit with a case design similar to that of a portable sewing machine.

Early versions of the Model 4 mainboard were designed to accept a Zilog Z8000 16 bit CPU upgrade board to replace the Z80 8 bit CPU but this option was never released.

ORIGIN U.S.A.
YEAR 1983
KEYBOARD Typewriter style 83 keys with numeric keypad
CPU Zilog Z80
SPEED 4 MHz
RAM 64 KB (up to 128 KB)
ROM 14 KB
TEXT MODES 64 x 16 / 32 x 16 / 64 x 40 / 80 x 24
GRAPHIC MODES None
DISPLAY Monochrome green phosphore
SOUND Built-in speaker
SIZE / WEIGHT 47.5 (W) x 52 (D) x 31 (H) cm
I/O PORTS Tape (500 or 1500 bauds), Centronics, I/O ports compatible with Model III, Serial (4D)
OS TRSDOS 6.0 or 1.3, LDOS, CP/M
POWER SUPPLY Built-in power supply unit
PRICE From $1990. In later years the price came down to about $1000
By 1990 the Model 4D was being closed out at $599

Our Model IV was very kindly donated by Edward Gladstone together with his vast collection of Tandy hardware, software and manuals.

Manufacturer: Tandy
Date: 1983

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Tandy TRS-80 Model IV Manuals:

Item	Manufacturer	Date
TRS-80 Colour Graphic Printer Manual	Radio Shack	Unknown
TRS-80 RS-232-C Interface Manual	Radio Shack	1978
The Electric Pencil for TRS-80 Operator's Manual	Small System Software	1978
TRS-80 Model III Disk System Owner's Manual	Tandy	1980
Instructions for Converting Specified Model I Programs for use on TRS-80 Model III	Radio Shack	Aug 1980
TRS-80 Model I/III Series 1 Editor Assembler	Radio Shack	1981
Trackcess 3.0 "Access to Tracks"	The Alternate Source	1981
TRS-80 Model III Technical Reference Manual	Tandy	1981
TRS-80 Model 100 Portable Computer Owners Manual	Radio shack	1983
Tandy TRS-80 Model 100 Quick Reference Guide	Tandy	1983
TRS-80 Model 4/4P Disk System Owner's Manual	Tandy	1983
TRS-80 Model III Hard Disk System Start-up Manual	Tandy	1984

Magazines RELATED to Tandy TRS-80 Model IV in our Library

Item	Manufacturer	Date
REM 80 - Volume 3, Issue 4	The North West TRS-80 USers Group	Unknown
REM 80 - Volume 4, Issue 2	The North West TRS-80 USers Group	Unknown
REM 80 - Volume 4, Issue 4	The North West TRS-80 Users Group	Unknown
REM 80 - Volume 5, Issue 2	The North West TRS-80 Users Group	Unknown
REM 80 - Volume 5, Issue 3	The North West TRS-80 Users Group	Unknown
REM 80 - Volume 5, Issue 4	The North West TRS-80 Users Group	Unknown
REM 80 - Volume 7, Issue 1	The North West TRS-80 Users Group	Unknown
REM 80 - Volume 6, Issue 5	The North West TRS-80 Users Group	Unknown
REM 80 - Volume 8, Issue 4	The North West TRS-80 Users Group	Unknown
REM 80 - Volume 9, Issue 4/5	The North West TRS-80 Users Group	Unknown
REM 80 - Volume 8, Issue 3	The North West TRS-80 Users Group	Unknown
REM 80 - Volume 11, Issue 1	The North West TRS-80 USers Group	Unknown
REM 80 - Volume 6, Issue 1	The North West TRS-80 Users Group	Unknown
REM 80 - Volume 7, Issue 4	The North West TRS-80 Users Group	Unknown
REM 80 - Volume 9, Issue 6	The North West TRS-80 Users Group	Unknown
REM 80 - Volume 6, Issue 3	The North West TRS-80 Users Group	Unknown
REM 80 - Volume 9, Issue 1	The North West TRS-80 Users Group	Unknown
REM 80 - Volume 9, Issue 2	The North West TRS-80 USers Group	Unknown
Popular Electronics - October 1977		Oct 1977
Personal Computer World - August 1978		Aug 1978
Personal Computer World - September 1978		Sep 1978
Personal Computer World - October 1978		Oct 1978
Practical Computing - October 1978	ECC	Oct 1978
Practical Computing - November 1978	ECC	Nov 1978
Practical Computing - December 1978	ECC	Dec 1978
TRS-80 Computing - Volume 1, Number 1	Computer Information Exchange Inc.	1979
Practical Computing - July 1979	ECC	Jul 1979
Practical Computing - August 1979	ECC	Aug 1979
Practical Computing - September 1979	ECC	Sep 1979
Practical Computing - November 1979	IPC Electrical Electronic Press	Nov 1979
Practical Computing - January 1980	IPC Electrical Electronic Press	Jan 1980
Practical Computing - April 1980, Volume 3, Issue 4	IPC Electrical Electronic Press	Apr 1980
Personal Computer World - June 1980		Jun 1980
REM 80 - Volume 3, Issue 1	The North West TRS-80 USers Group	1981
REM 80 - Volume 3, Issue 3	The North West TRS-80 USers Group	1981
Personal Computer World - July 1981		Jul 1981
Personal Computer World - September 1981		Sep 1981
Your Computer - December 1981		Dec 1981
TRS-80 Microcomputer News Volume 1 Number 1	Radio Shack - Tandy	Jan 1982
TRS-80 Microcomputer News - Volume 1, Number 2	Radio Shack - Tandy	Feb 1982
Personal Computer World - May 1982		May 1982
Personal Computer World - December 1982		Dec 1982
REM 80 - Volume 5, Issue 5	The North West TRS-80 Users Group	1983
REM 80 - Volume 5, Issue 6	The North West TRS-80 Users Group	1983
REM 80 - Volume 6, Issue 2	The North West TRS-80 Users Group	1983
Personal Computer World - August 1983		Aug 1983
TRS-80 Microcomputer News October 1983		Oct 1983
Practical Computing - October 1983		Oct 1983
Call-A.P.P.L.E. - November 1983		Nov 1983
REM 80 - Volume 7, Issue 2	The North West TRS-80 Users Group	1984
REM 80 - Volume 6, Issue 4	The North West TRS-80 Users Group	1984
Personal Computer World - February 1984		Feb 1984
The War Machine Issue No. 25 - March/April 1984		Mar 1984
Personal Computer World - May 1984		May 1984
Byte May 1984		May 1984
Personal Computer World - August 1984		Aug 1984
Byte March 1984		Oct 1984
REM 80 - Volume 7, Issue 5	The North West TRS-80 Users Group	1985
REM 80 - Volume 8, Issue 1/2	The North West TRS-80 Users Group	1986

Catalogues RELATED to Tandy TRS-80 Model IV in our Library

Item	Manufacturer	Date
TRS-80 Applications Software Sourcebook Volume 2		Unknown
TRS-80 Applications Software Sourcebook Volume 3		1981
TRS-80 and Genie Software	Molimerx Ltd	1982

Other Systems Related To Tandy TRS-80 Model IV:

Item	Manufacturer	Date
Tandy TV Scoreboard	Tandy	1976
TRS-80 Microcomputer System Model I (26-1003)	Radio Shack - Tandy	1977
TRS-80 Color Computer	Tandy	1980
Tandy 102 Portable Computer	Tandy Radio Shack	1983
TRS-80 Colour Computer 2	Radio Shack Tandy	1983
Tandy TRS-80 Model 4 P	Tandy	1983
TRS-80 Model 102 Portable Computer	Tandy Radio Shack	1983
TRS-80 Model 100 Portable Computer	Tandy Radio Shack	April 1983
Tandy Color Computer 3 (CoCo 3)	Tandy	30th July 1986
Tandy 1000 EX Personal Computer	Tandy	December 1986
Tandy 1400 Professional Computer LT	Tandy	1987
Tandy 1000 HX Personal Computer	Tandy	1987
Tandy 1100FD Laptop Computer	Tandy Radio Shack	November 1989