10 Feb
2006
10 Feb
'06
12:41 p.m.
On 2/10/2006 at 12:01 PM Don North wrote:
Now you know why RISC architecture is so popular...
this all took 4KW of
96b wide micro code in the CISP and another 512W of 64b wide code in the
base 11/74
CPU.
Interesting--the lower CDC Cybers (72,73 and probably the 172, 173) had an
option for a CMU "Compare/Move Unit", which implemented varioius 6-bit byte
oriented operations. The 74 and 174 didn't implement it.
Interestingly, the 6600/74/174 without the CMU could pretty much bury any
other "commercial instruction set" CPU available running COBOL. There are
some pretty nifty bit-twiddling tricks that a 1's-complement arithmetic
instruction set operating on wide (for the time) words can perform that
pretty much makes a CMU-like box redundant, particularly on a
parallel-issue architecture like the 6600.
Cheers,
Chuck