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Tandy Radio Shack

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 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 (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.

Please consider donating your old computer / videogame system to or one of our partners from anywhere in the world (Europe, America, Asia, etc.).

Special thanks to Charles Harris who donated us this computer !


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

Tuesday 22nd September 2020
Jay (Washington State USA)

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.

Friday 11th September 2015
David Coffey (Florida, United States)

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.

Friday 11th September 2015
David Coffey (Florida, United States)


MANUFACTURER  Tandy Radio Shack
TYPE  Professional Computer
YEAR  1983
KEYBOARD  Typewriter style 83 keys with numeric keypad
CPU  Zilog Z80
RAM  64 KB (up to 128 KB)
ROM  14 KB
TEXT MODES  64 x 16 / 32 x 16 / 64 x 40 / 80 x 24
COLORS  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)
BUILT IN MEDIA  One or Two 5.25'' disk-drives
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

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