One's complement - was Re: Rich kids are into COBOL
cclist at sydex.com
Mon Mar 2 01:43:27 CST 2015
On 03/01/2015 03:05 PM, Toby Thain wrote:
> Studying the CDC 6000 instruction set (through the Grishman book) really
> gives me the impression one's complement would be quite a headache to
> use correctly.
It wasn't, trust me. Because the long add unit on the 6600 used a
subtractive algoritm, negative zero was pretty uncommon as a result of
Either value registered as zero for the conditionals--remember, no
condition codes. The big difference is that negative zero registered as
minus. Remember that on X-register tests, you could, with a single
instruction, only branch on zero/nonzero or minus/plus.
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