The Ultimate Acorn Archimedes talk

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qwertyface
Posts: 14
Joined: 16 Jul 2019, 09:19

The Ultimate Acorn Archimedes talk

Post by qwertyface » 12 Mar 2020, 11:16

I just watched this talk from 36C3 on the design of the Acorn Archimedes computer, and I really enjoyed it. I thought it might be of interest to people on here.

In particular I was fascinated by some of the details of how how the chipset was designed to fit within constraints of pin-count on packages; why the ARM used 26-bit addressing; why it has the load and store multiple instructions; the effect of memory bandwidth on system performance and most of all the emphasis on a "balanced design" of a whole system. As I learn about the Gigatron in more and more detail, I can see that "balance" and designing the whole system not just components is the only thing that makes it work. The computers are very different systems in many respects, but I think they have something in common.

On the CCC website
On YouTube

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marcelk
Posts: 472
Joined: 13 May 2018, 08:26

Re: The Ultimate Acorn Archimedes talk

Post by marcelk » 12 Mar 2020, 22:28

Nice find! My cookies told me I already watched it, but I half forgot about this talk. Indeed there are similar lines of thought popping up in several places. And it is always a bit hard to see things that were avoided unless somebody points them out. For me the best is that, after watching again, putting data on the address bus doesn't feel as dirty any longer.

It's also interesting to see unintended consequences of chasing some specific goals:

In the case of the ARM CPU, originally it was about simplicity (because of inexperience in IC design) in combination with low power usage (to avoid expensive ceramic packages). Later this led to application in Nokia cell phones: tiny cheap low-power processors.

In our case it originally was mostly about staying well below 40 TTL chips (because the tongue-in-the-cheek Break Out comparison) in combination with avoiding esoteric instruction sets (so we wouldn't be left with yet another home brew that doesn't have real software). The result turns out to be quite "kit-able": easy to build, somewhat entertaining and not costing so much that it hurts.

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