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TRS-80 Model IV

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Early Intel and Zilog CPU

based portable personal



TRS-80 Model I

TRS-80 Model III

TRS-80 Model IV

Color Computer

Color Computer 2

Color Computer 3



Early ultra-light personal

computers based on Intel

and Zilog CPU's.  These

units are all unique in

their class.

TRS-80 Model II

Tandy Model 12

Tandy Model 16, 16b



Once again systems

caught between CPU


TRS-80, Tandy 2000

Tandy 1200

MC 10



Simply the best personal

computers built. 

Operated under MS-DOS

2.11 to 6.22.  Based on

the IBM PC. Jr.

Tandy 1000, 1000a

Tandy 1000SX ,1000TX

Tandy 1000 SL,TL & TL2

Tandy 1000EX, 1000 HX

Tandy 1000 RL, RLX

Introduced: 1983
CPU: Zilog Z-80A, 4.0 MHz
RAM: 64K (expandable to 128 K)
Ports: Tape (500 or 1500 bauds), Parallel & RS232

Display: 12" Green Phospher 

64 x 16 / 32 x 16 / 64 x 40 /

 80 x 24
Storage: Two internal 178K

floppy drives,

External hard drive
Operating System:


I promised myself that I would not

get personal about a computer,

after all it's rather unhealthy, but here is where I make an exception.  The Model 4 is a

great machine.  So much so, that although I work in the IT field, usually preach to get the

latest and greatest, I still use a Model 4 today.


The model 4 is to computers as soccer (football) is to sports.   Like the Canada's AVRO

Arrow fighter jet,  the fate of the Model 4 is as frustrating.  The first Model 4 came out with

64K RAM, with two single sided 5.25" floppy drives, a serial port and external floppy drive

connectors.  Tandy, like the Model 3, put an I/O edge card into it that you could literally

be used to interface with anything your mind could think of.  Today you are still able to

buy an IDE interface that connects to this port and allows you to run IDE hard Drives, with

7 MB.  to 12 MB. partitions.


The second release of the Model 4

was the gate-array unit.  Notable

differences were the serial port

reconfigured to cable out the back

instead of straight down, and a new

improved keyboard.  This included

arrow keys positioned to the lower

right of the QWERTY layout.  The

circuitry was integrated better and

one were a few trace wires

prevalent in the early models.


The display of the Model 4 was

also superior over the Model 1 and

3's.  With a 80 x 24 character

display, one could also add a

graphics adaptor which the Model 4

display hi-resolution.  An interesting feature was  that the graphics board stored the

graphics layer into memory which could be brought forward easily when programming



Tandy produced a portable version of the Model 4 dubbed the Model 4p.  This unit had a

smaller display and unlike its desktop version (tongue in cheek) could not boot up into a

Model 3 mode.  This unit had a detached keyboard, and internal expansion for an internal

modem.  A great unit for the business person on the go!


The final release of the Model 4

was the 4D.  This is were Tandy

shone.  Few were sold and they are

very collectable.  This unit cleaned

up the gate-array main board

completely and added double

sided 5.25" floppy drives.


Overall the Model 4 lives on because of the vast amount of

software available.  One just has to look for it.  Today I have a "fully' expanded Model 4

gate-array unit running 128 K RAM, graphics board, 3.5" double sided floppy and a 5.25"

double sided floppy,  A 40 MB. IDE hard Drive, 9600 baud modem and a two button

Microsoft Mouse.  The operating system of choice is the LS-DOS 6.2.  This system allows

for the formatting of the drives configured, and very flexible utilities.  Running 4.0 Mhz, no

one can catch me! :-)


One other note, it is possible to log into the internet using Mel Patrick's Fasterm emulating

a VT-100 terminal.  Just ensure that you dial up to a Xenix server.  (More about this later)

Images from top to bottom:  TRS-80 Model 4 (Gate Array), TRS-80 Model 4p and the

Tandy Model 4D




(c) 2004, 2005 Brian K. Hahn

 All Rights Reserved.