From: filibert@vista (Daniel Filiberti)
Newsgroups: comp.sys.next.advocacy
Subject: Re: processor comparison(longish)
Date: 6 Jan 93 20:13:20 GMT
Article-I.D.: ohsu.1993Jan6.201320.9493
Reply-To: filibert@ohsu.edu
Organization: Oregon Health Sciences University

In article <1993Jan5.220545.22030@murdoch.acc.Virginia.EDU>  
clc5q@hemlock.cs.Virginia.EDU (Clark L. Coleman) writes:
> 
> 1) MIPS are marketing hype.  "400 MIPS" is a worthless number to
> use when evaluating the Alpha.

I wasn't "evaluating", just comparing the Alpha with the
PA-4.  There were MIPS quotes in the article that I was
reading for both processors, and that is where I obtained
the numbers.  If you read my post, I also quoted a passage
from the article that stated the 150 MHz Alpha beat the HP
730 PA-RISC.  There were no formal benchmarks for the
Alpha at the time, but it was estimated to run at 110
SPECmarks.  In the latest IEEE spectrum, the formal
benchmarks are now available. 

> 2) By reasonable benchmarks (SPECint92 and SPECfp92), the 99 MHz PA-7100
> is slightly faster than the 150 MHz Alpha workstations that were just
> announced.

Agreed.  The 99MHz PA is slightly faster than the "first"
release of the Alpha.   Who cares? 

> 3) I want performance on real codes, not MHz. See #2 above.

The point is that the designers of the Alpha determined
that the Alpha would have to achieve a performance boost
by a factor of 1000 to last for over a decade.  They decided
that the performance increases would come from
increased clock speeds, by a factor of 10 before reaching
their upper limit. 

> 4) Don't believe the breathless hype from DEC. They are desperate to
>    sell everyone on the Alpha in order to recover from their recent
>    woes.  Comparing it to previous generations of competitors' machines
>    is par for the course.

Whatever.

> The 99 MHz HP systems have large primary caches (256KB each, instruction
> and data.)  This is implemented on external SRAM (just about the fastest
> available.) No secondary cache is used.  The Alpha has small on-chip caches
> (8KB each) and then accesses secondary cache over an off-chip bus that is
> slower than the CPU clock (e.g. 75 MHz for the 150 MHz systems, I believe.)
> The HP will therefore run at 0 wait states much more often that the Alpha
> machines of today.

The first test versions of the Alpha (codenamed the EV-3)
used CMOS-3 and had an external primary cache similar to
the HP line.  This was scrapped in order to implement the
Alpha in CMOS-4.  Accessing external SRAM isn't faster
than the on-chip caches, is it?  Furthermore, the Alpha
has a Bus Interface Unit that is configurable to the
external cache size and access time, employ either ECL or
TTL, and control the clocking rate of the BIU.  It seems
that having the caches on chip allows the higher clock
rate, and is an advantage to having them external (ie; the
HP requires the external cache, it is a 2 component
processor).  The reason that the Alpha will have "wait
states" is because it is running at about double the clock
rate of the HP processor.  Why is this necessarily bad? 

> Comparing such dissimilar CPU/cache designs strictly by the internal clock
> speed is pointless.  And, as with the MIPS R4x00 family, there are two
> clock speeds that you would have to talk about; likewise with the clock
> doubling chips from Intel.

Not if you believe that increases in clock speed will
account for most of the performance increase in
processors for the next decade or so.  That is the vision
for Alpha, apparently. 

> The 182 MHz Alpha systems are faster than the 99 MHz HP systems, and the
> upcoming 200 MHz systems will be another 10% faster.  But HP is working on
> new systems, as well. I predict that there will not be a time in 1993 in
> which Alpha workstations are as much as 50% faster than HP at the high end,
> yet DEC marketeers continue to befuddle people with that number.

I predict that you are wrong.

> By the way, the 150 MHz Alpha workstations were announced on the same day
> in November as their 99 MHz betters from HP.  This was after a year of
> vaporous marketing from DEC that claimed they had a chip that was twice as
> fast as any chip from the competition (e.g. talking about 200 MHz Alpha chips
> in the labs in January of 1992 and comparing them to actual systems that had
> been shipping in the 1000s for many months.)  This kind of hyperbole is
> associated with desperation in my mind.

They weren't just talking 200MHz, they will deliver in
1993.  The Alpha does run twice as fast, but that doesn't
mean that it performs twice as well.  It remains to be seen
as to what happens with Alpha, but it has a good start, was
designed with its future in mind, and seems to be a good
product.  What else do you want? 

An Alpha-based NeXT computer, perhaps?

> -- 
> --------------------------------------------------------------------------
> "It is seldom that any liberty is lost all at once." David Hume
> |||  clc5q@virginia.edu (Clark L. Coleman)

Daniel Filiberti
---
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Motto for a monitor, "It's better to burn out, than to fade
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Daniel Filiberti
Oregon Health Sciences University
Biomedical Information Communication Center (BICC)
3181 Sam Jackson Park Road
Portland, Oregon  97201-3098
email:  filibert@ohsu.edu
Newsgroups: comp.sys.next.advocacy