[ale] OT: AMD Athlon 64

[James P. Kinney III]

True. Unless the CPU is a dual-core multi-GHz monster and the board only
holds 64MB RAM.

RAM is key for multiple tasks as used on most modern environments (word
processors are mostly huge ram hogs). The more you have, the "zippier" the
system "feels".

Up to a point.

CPU speed is still the rate limiter for many operations. It doesn't matter
if you have loads of RAM if the cpu is not fast enough to work with it in
a timely manner. That is where chipset issue show up (except for the
opteron cpu's which do their own memory management) and the mobo become
critical for the operation.

There have been many system built that use a weak chipset compared to the
cpu speed. What happens here is the cpu can request a memory section and
then it has to wait for the chipset to deliver it. CPU makers started
working around this by adding look-aheads (and the linux kernel was among
the first systems to make use of it) which retreive the memory so that it
is available on the next clock tick after the request occurs.

This works great when the mating between CPU speed, chipset and RAM timing
is good. It is disasterous when it isn't. If the fetching process gets too
far out of order, the wrong memory address gets delivered and the system
can lockup (worst case scenario) or the system slows to a crawl while the
out-of-order pipeline gets rearranged to realign the memory hitting the
cache with the requests in the cache.

This was the case up until uber-cool cpu's like the opteron came along.
They have their memory management on the cpu die so it runs at the same
speed as the chip. This makes for a screaming fast memory allocation
process along with a built-in numa ability. But this requires a very close
matching of RAM  clock with CPU clock.

The 8xx series Opteron chips can pass memory info "out-of-band" between up
to 8 cpus at the same rate they can move ram into and out of cache! So
each cpu knows at any time where the needed ram is and can get it just as
fast as if it were in the adjacent RAM bank.

Granted, SGI was doing almost this process 10 years ago and Cray was doing
exactly this process 20 years ago. But's way cool having the equivalent of
a 20 year old Cray is a box that fits under a desk and doesn't take a
20-ton AC unit to cool it! If only I could convince "She who must be
obeyed" that I really, really need on of those 8-way Opteron monsters...

> Here's a quick question: When it comes to owning a computer that won't
> annoy you (as in, taking forever to open/close/switch applications),
> isn't it true that a full bank of RAM is more useful than a hefty
> processor?
>
> Jesse M. Holmes
>
> -----Original Message-----
> From: ale-bounces at ale.org [mailto:ale-bounces at ale.org] On Behalf Of
> Brian Pitts
> Sent: Friday, May 05, 2006 4:00 PM
> To: ale at ale.org
> Subject: Re: [ale] OT: AMD Athlon 64
>
> John Wells <jb at ...> writes:
>>
>> Anyone out there know of a good, easy-to-digest treatise on the
> subject?
>> What would you recommend?
>>
>
> The Athlon 64 3000 (Socket 939, Venice core) is $114 at Newegg; that
> seems like
> a real steal. There also have nForce4-based motherboards from Asus and
> MSI for
> around $80. It's better hardware at not much more cost than the
> processor/motherboard combo Fry's advertised this week for $160.
>
> -Brian
>
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