Subject: PowerPC vs. RS/6000 (RIOS1) comparison...

From: [email-masked] (Joe M Leonard)
Date: Wed, 27 Jul 1994 20:26:29 -0400

Recently, Joerg-Ruediger Hill posted...

     The PowerPC (chip) is a single chip microprocessor which was
developed using the existing IBM RS/6000 CPU, but squeezing it onto one chip.
Naturally, this could be done only by leaving out some of the features (the
PowerPC instruction set is only a subset of the RS/6000 CPU ones). So the
PowerPC chip is significant slower than the IBM RS/6000 CPU.

He also included some run-times which idn't seem to include PowerPC times
(the RS/6000 25T workstation)...

I don't think the blanket statement that the PowerPC chip is significantly
slower than the RS/6000 is correct - certainly not against the older
members of the family.  Remember that the PowerPC chip runs at a higher
MHz rating than many/most of the RIOS1 family (i.e. all but the 390/590
recently developed - the RIOS2 chipset).  This has a noticeable effect
on things like graphicx/X and compilations, things which aren't
terribly dependent on pipelined Real*8 operations.

While I don't have the exact numbers to back it up, I expect that the 25T
workstation (with the PowerPC/601 chip in it) is essentially the
same as an R4000 indigo (the older 50/100 chip?).  This would make
it about the x50 or x60 RIOS1 RS/6000 in speed.  Perhaps some of the hardware
folks getting this net would be so kind to publish Linpack 100x100 or 
SPECfp92 numbers for the pertinent IBM machines (like the 550, 370/37T,
25T, etc.).).

Joe Leonard
[email-masked]

Please direct IBM/SGI comparison flames to me, not the net
(or to /dev/null :-)