14-06-2024, 01:24 PM
(This post was last modified: 14-06-2024, 01:25 PM by ppppenguin.)
The PM5544 circle memory moved from core to some kind of ROM in early 1970s. That was for about 2k bits. The 1702, the first EPROM, was 256x8. It was introduced in 1971. I think the later PM5544 used a National mask programmable 256x8 ROM (the scanned manual posted online isn't clear enough to be certain) with a number like MM5210. Though this data book says it's only 256x4: https://www.retrotechnology.com/dri/NatS...77_300.pdf
Having crawled all over it for many hours, I'm getting less and less impressed by some of the design. I know it was done before even MSI logic such as four bit counters were available, let alone synchronous counters like the '161, but there is any amount of bad practice. Leaving aside all the RC differentiators and suchlike, the worst offence is that the circle width and position are determined by analogue adjustments. Even back then in 1971, I don't think it would been much harder or more complex to make the circle digitally correct by design.
Having crawled all over it for many hours, I'm getting less and less impressed by some of the design. I know it was done before even MSI logic such as four bit counters were available, let alone synchronous counters like the '161, but there is any amount of bad practice. Leaving aside all the RC differentiators and suchlike, the worst offence is that the circle width and position are determined by analogue adjustments. Even back then in 1971, I don't think it would been much harder or more complex to make the circle digitally correct by design.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
