Reproducing old machines with newer technology (Re: PDP-12 at the RICM)
cclist at sydex.com
Wed Jul 15 16:54:51 CDT 2015
On 07/15/2015 01:30 PM, ben wrote:
> Quick look on the web ... ARG! Max segment length 64K something.
Well, even in the late 70s, 64KB was still a goodly chunk of memory in
the microprocessor world. Which reminds me...
To bore you with another STAR tale--the machine had two page sizes--the
"small" page, which was 512K 64-bit words and the "large page", which
was 64K words. What some smart-alec discovered was that in a 512Kw
system, it was possible (easily) to write an instruction that could
never get started. You could have up to 6 addresses in a vector
instruction (3 operands+3 control vectors). Storage was managed in 512
bit "super words". Start your large-page job, put two of the operands
near the end of a page and bingo--you get 8 page references just to get
the instruction started. Of course, the solution was to sell the
customer more memory...
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