Talk:SDS Sigma series

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Instruction format[edit]

I suspect the instruction format was the same for all 32-bit Sigmas, but hesitated to say so without checking the manuals. — Preceding unsigned comment added by Peter Flass (talkcontribs) 06:46, 22 January 2012 (UTC)‎

OK, I checked the Sigma 5/6/7/8/9 manuals at The general format just has a 17-bit address field; the different interpretation depending on the high-order bit of that field is specific to the Sigma 9 in if "real extended addressing", which is a mode that allows non-virtual access to more than 128K words of physical memory, is in effect.
The manuals also describe a different format for immediate instructions, so I left this as just describing memory-reference instructions. Guy Harris (talk) 02:24, 23 January 2012 (UTC)


"At the time the only competition for the Sigma 7 was the IBM 360."

What does this mean? In which space did the Sgma 7 and IMB 360 compete? It seems to me the PDP-6 was also a competitor. Lars Brinkhoff —Preceding undated comment added 06:33, 1 February 2017 (UTC)

Since only 23 PDP-6s were sold, it doesn't seem that they were much of a competitor. But the PDP-6 led to the PDP-10, which could have been a competitor. Gah4 (talk) 07:47, 1 February 2017 (UTC)