Linux performance on 21066 (UDB)

Perry Harrington (pedward@sun4.apsoft.com)
Fri, 6 Feb 1998 20:00:35 -0800 (PST)

When I initally tried Linux on a UDB, I was very disappointed. What has lead
me to believe that there is a significant performance increase to be had is
this: The 21066 DEC reference paper says that the low memory bandwidth of
the 21066 is not a big hinderence since it can do tagged queuing of memory
fetches, fetch a 256bit cache load in 4 cycles, and can issue 2 RISC
instructions at once. Now this may seem like nothing next to a Pentium,
consider that a Pentium has microcode, and certain instructions can stall
the dual issue mechanism, from what I understand, the Alpha can essentially
execut ANY 2 instructions at once, even memory operations (I belive that it
can have 4 memory ops out at once?). So the questions are these:

Am I likely to see any performance boost on the 21066 (UDB/Multia) in the
future, due to coding changes and deliberate work to quad-word align Linux
functions/data/etc. Second, is the 21066 really capable of performing well,
or is it a lost cause? The fact that it performs like a 486-75 is upsetting,
it's ONLY feature is that it can push 10Mbs out the 21040, a very respectable
router in my opinion.

Thanks,
Perry

-- 
Perry Harrington       Linux rules all OSes.    APSoft      ()
email: perry@apsoft.com 			Think Blue. /\
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