Subject: Re: NetBSD/i386 processor recommendation
To: None <WOFerry+@CMU.EDU, port-i386@NetBSD.ORG>
From: Ross Harvey <ross@teraflop.com>
List: port-i386
Date: 08/05/1997 18:50:27
My recommendations:
Forget P5. Forget MMX. Go P6. NetBSD is exclusively 32-bit
code, and the P6 will give you 3-way integer + 1-way FP
superscalar dispatch _with_ out-of-order execution. This is why
it is so much faster (on 32-bit code) than older chips, even
when compared with higher clock rate alternatives.
Yes, it will more than make up for the 25% MHz difference, and
it will cost a LOT less. Also, the low clock rate gen-U-ine
in-tel CPU's can almost always be overclocked. Your odds of
overclocking a fast chip are somewhat lower.
Despite hype to the contrary, the Pentium II does not really
have a performance advantage over the P6. It is mostly a
repackaged P6, with two additions that won't help you: MMX and
better 16-bit performance, one addition that might: larger
caches, and one that will hurt you: slower secondary cache.
And of course it has a totally difference socket. I think this
chip mostly benefits Intel, they get better yields and can push
more MMX snake oil. (You've gotta have MMX or else, uhh, well, uhh,
you just gotta have it, trust us, we're intel. We would know,
right?)
Buying a 150 MHz P6 is a very smart choice. I got one at Fry's
many months ago for $181, and the next week they were down to
$168. Even less now...they are a great deal. At the time I was
there the P5+MMX chips were going for TWICE the price of a P6
at the same clock rate, and a high clock rate P5 was way more
expensive than a lower clock rate P6. Go figure. I guess people
just look at MHz.
It is true that the newer chips (P5+MMX, P6+MMX==P II) have
larger primary cache sizes, and a given P II has a much bigger
but much slower (1/2 speed of P6) secondary cache. This does
not benefit every application, however. The only thing that
makes PII go faster than P6 is a higher clock rate and bigger
cache.
From other mfrs, the AMD K6 actually appears to be respectable,
unlike the K5 which was kind of a joke.
I'm not sure why you think the bus speed will be better with
the P5. The PCI bus speed just depends on whether the integer
divisor from the CPU speed can hit 33 MHz, or whether you have
to settle for a slightly lower speed like 25 MHz. But who
cares? There is no memory on the PCI bus, PCI at 25 MHz is
still able to do 100 MB/S, which is a lot faster than your
drive. (Drive max: IDE=700KB, EIDE=7MB, SCSI=5-40, but more
likely 5 than 40!) People with wide ultra scsi controllers and
expensive graphics might notice the bus speed difference, but I
doubt if most people would care.
----------------------
Ross Harvey Avalon Computer Systems, Inc. ross@teraflop.com
Santa Barbara http://www.teraflop.com