Found this in a newsgroup today...very interesting..
-=----------------------------------
>From Empire.Net!ultra.i1.net!news.inlink.com!news.dra.com!feed1.news.erols.com!cpk-news-hub1.bbnplanet.com!news.bbnplanet.com!su-news-hub1.bbnplanet.com!news.sgi.com!uhog.mit.edu!news.media.mit.edu!trims Fri Dec 13 02:58:30 1996
Path: Empire.Net!ultra.i1.net!news.inlink.com!news.dra.com!feed1.news.erols.com!cpk-news-hub1.bbnplanet.com!news.bbnplanet.com!su-news-hub1.bbnplanet.com!news.sgi.com!uhog.mit.edu!news.media.mit.edu!trims
From: trims_at_media.mit.edu (Erik Trimble)
Newsgroups: misc.forsale.computers.workstation
Subject: AXP-based Machines (Was: DEC Alpha 166 For Sale)
Date: 11 Dec 1996 05:15:40 GMT
Organization: Perceptual Computing, M.I.T. Media Lab
Lines: 149
Sender: trims_at_ongar.media.mit.edu (Erik Trimble)
Distribution: world
Message-ID: <58lg1s$r0j_at_hpns1.media.mit.edu>
References: <zayanya-ya023080000312962117460001_at_news.erols.com> <5833o5$nlq_at_portal.gmu.edu> <58fpc9$1ru_at_solaris.cc.vt.edu> <58gl8r$1ge_at_ultranews.duc.auburn.edu> <58hfn8$4ik_at_solaris.cc.vt.edu> <58ho09$q16_at_portal.gmu.edu>
NNTP-Posting-Host: ongar.media.mit.edu
X-newsreader: xrn 7.03
OK. We of course have seen much too much on this subject, so I though it would
be appropriate to cover some very important topics in making an informed
decison about buying an Alpha AXP-based machine vs an Intel-based one.
1. Cache
L2 cache in an AXP-based system is critical. The larger size of most data
structures in a 64-bit design vs. the 32-bit design of the Pentium/PPro requires
considerably more external cache. The on-chip caches of the various AXP chips
vary (with the 21066A having but 16kB, the 21064A having 32kB, and the 21164A
having 112kB (combined). The 21066 is extremely crippled if there is no external
cache, and any cache under 1MB is a drain. The 21064 and 21164 generally must
have 1MB, and really should have at least 2MB of secondary cache in order to avoid
a major bottleneck. While 20ns cache speed works, 15ns or 10ns cache speeds are
preferred. Typical Intel-based cache speeds are 20ns.
Adding 256kB pipeline cache to an Intel CPU generally gives it a 10-15%
performance boost. Adding 256kB to a 21066 gives it about a 15% boost over a
no-cache 21066, while a 1MB cache will result in about 40% better performance.
(Imagine what the cache-less performance is. Yuk.). A 21064 or 21164 with 2MB
instead of 1MB performs about 15% better, growing to about 20-25% better with and
8MB cache.
SECONDARY CACHE SIZE IN AN ALPHA IS EXTREMELY IMPORTANT.
Cache sizes in various AXP-based products
Product CPU Cache
Multia VX40 21066A 256kB (fixed)
Multia VX41/42 21066A 256kB - 1MB (upgradable)
AXPpci33 eval boards 21066A 256kB or 1MB (upgradable)
AlphaStation 200 21066A 512kB
DEC 3000/300 21064 1MB
AXPpci 233XL 21064A 1MB
AlphaStation 400 21064A 512kB
DEC 3000/600 21064 2MB
AXP PCI 64 oem boards 21064A 512kB-4MB (upgradable)
AlphaStation 255 21064A 1MB
AXP PCI 164 oem boards 21164 512kB-4MB (upgradable)
AlphaStation 500 21164 2MB or 8MB
2. Memory bandwidth
In general, this refers to the speed with which data can be moved
back and forth from main memory. This is usually directly related to the
width of the bus (with a couple of other factors added in). In 21066-based
machines, 64-bit wide memory bus is in place. Low-end 21064 machines also have a
64-bit memory bus, while higher-end machines have 128-bit wide buses. 21164-based
Alphas almost always have 128-bit or wider memory architectures. The higher-end
Alphas often have even more specialized circuitry for accessing main memory.
Remember, since the Alpha wants information in 64-bit chunks, high memory
bandwidth is more important than the 32-bit Intel CPUs. For comparison, most Intel
machines have a slow 64-bit memory bus, while some of the most advanced have a
high-speed 64-bit memory bus (virtually no Intel motherboards uses a 128-bit
memory bus). If an Intel and Alpha use the same memory width and equivalent
architecture, the Alpha will fare worse than the Intel.
3. Megahertz (RISC vs CISC)
The RISC vs CISC argument is increasingly irrellevant, as modern Intel
chips include a wide variety of RISC techniques to speed things up. However, it
is useful to look at the design philosophies of the two chips: the Alpha
architecture was designed as a "pure" RISC, with a very small instruction set
(about 5 dozen very small instructions). Consequently, it uses a large number of
short pipelines and extremely high clock rate to achieve performance. While it is
generally possible to do a few items simultaneously on an Alpha, each instrcution
does fairly little. However, the high clock rate compensates for this.
The Intel Pentium and Pentium Pro, however, evolved out of a CISC design.
They are exceedingly complex chips with a large instruction set (over 15 dozen),
and only a few pipelines, of which only 3 or so can execute simultaneously.
However, each instruction can "do" quite a bit, resulting in a larger amount of
work done at each step, but fewer steps than an Alpha.
Thus, the two architectures can't really be compared on megahertz.
The above all said, here are some good general rules of thumb that I have observed
from running Linux and WindowsNT on both the Alpha and Intel platforms:
(when Intel equivalent are given, the system is assumed to be:
all Pentiums are assumed to have 32MB of RAM, 256kB pipeline burst cache,
Pentium Pros are assumed to have 64MB RAM, 256kb cache module)
( - means about 10% slower than, + means about 10% faster than)
Equivalent
Product CPU Cache Memory Int FP
Multia VX40 21066A-166 256kB 24MB P75- P75
Multia VX41 21066A-166 512kB 24MB P75 P90-
Multia VX41 21066A-233 512kB 24MB P90+ P100
Multia VX42 21066A-233 1MB 24MB P100+ P120
AXPpci33 eval boards 21066A-233 1MB 32MB P120- P120+
AlphaStation 200 21066A-233 512kB 32MB P100+ P120
DEC 3000/300 21064-175 1MB 32MB P100+ P150+
AXPpci 233XL 21064A-233 1MB 32MB P166 P200+
AlphaStation 400 21064A-233 512kB 64MB P166- PP150-
DEC 3000/600 21064-175 2MB 64MB P133 P166+
AXP PCI 64 oem boards 21064A-275 1MB 96MB P200- PP150+
AlphaStation 255 21064A-233 1MB 96MB P166 PP180-
AlphaStation 255 21064A-300 1MB 96MB P200 P180+
AXP PCI 164 oem boards 21164-266 2MB 128MB PP200 2xPP150
AXP PCI 164 oem boards 21164-300 4MB 128MB PP200+ 2xPP166
AlphaStation 500 21164-333 2MB 128MB 2xP166 2xPP180
AlphaStation 500 21164-400 2MB 128MB 2xPP150 2xPP200+
AlphaStation 500 21164-500 8MB 128MB 2xPP180+ 3xPP200
In general, having less than 32MB in a 21066, 64MB in a 21064/21064A, and 96MB in
a 21164 is detrimental; 48MB/96MB/128MB is the optimal memory for general use of a
21066/21064/21164.
Note that the above are not based solely on SPECint/SPECfp, but also the "feel" of
various WinNT apps, comparison compiles under Linux, and various other "fuzzy"
benchmarking. Your Mileage May vary.
The Multia is appealling in its different incarnations because you can make a 1GB
disk/32MB RAM/ethernet/sound/graphics Linux box for about $1000, tops. It's not
particularly fast, and doesn't run Win95 (though many x86 apps will run at
reasonable speed using WinNT AXP and FX32!), so a $1500 P-166 is probably a better
choice for a personal machine. However, the Multia makes a wonderful router,
terminal server, FTP or Web server.
Just hoping to clear up some confusion.
-Erik
Sponsored Research Technical Staff
MIT Media Lab
trims_at_media.mit.edu
--
"On two occasions I have been asked [by members of Parliament], 'Pray,
Mr. Babbage, if you put into the machine wrong figures, will the right
answers come out?' I am not able rightly to apprehend the kind of
confusion of ideas that could provoke such a question."
--from the writings of Charles Babbage
--
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
-= Dave Nye http://www.empire.net/ Internet Access Provider =-
-= President - Empire.Net Inc. for New Hampshire & Mass. =-
-= For information on our services send E-mail to info_at_empire.net =-
-= or call us _at_ (603) 889-1220, or FAX us _at_ (603) 889-0366 =-
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Received on Fri Dec 13 1996 - 09:32:20 NZDT