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TonyDuell · 1st May 2020, 12:43 pm

I have an idea that IC4 was a 1K*8 RAM (1K byte) possible a 4118. IC4a and IC4b were 1K*4 RAMs so you needed 2 for the 1K bytes. I think they were 2114 chips, a device that I regard as being 'change it if you get odd symptoms', the 2114 is possibly the most unreliable IC I've ever seen. A given board would have one or the other type of RAM, I think the pair of 2114s is a lot more common.

1st May 2020, 12:43 pm	#307
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,208	Re: Zx81 I have an idea that IC4 was a 1K8 RAM (1K byte) possible a 4118. IC4a and IC4b were 1K4 RAMs so you needed 2 for the 1K bytes. I think they were 2114 chips, a device that I regard as being 'change it if you get odd symptoms', the 2114 is possibly the most unreliable IC I've ever seen. A given board would have one or the other type of RAM, I think the pair of 2114s is a lot more common.