Thread: Zx81
View Single Post
Old 1st May 2020, 12:19 pm   #308
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 8,623
Default Re: Zx81

A quick shufty at the diagram linked to in #286 shows that the RAM can either be a single 8-bit wide IC (IC4) or two 4-bit wide ICs (IC4a and IC4b).

It so happens that both of my ZX81s originally had a single 4118 fitted, although both have now been replaced with 62256 SRAMs to give the machines 16K of internally fitted RAM. (The 'spare' 16K in the other half of the 32K IC is not utilised).

Apart from making it usable while still retaining Rick Dickinson's classic design looks - the basic ZX81 is not a bad looking machine at all - doing it that way spells an end to the horrors of RAM pack wobble.
SiriusHardware is online now