Re: 4-way Opteron vs. Xeon-IBM X3 architecture

• From: Rob Stow <rob.stow@xxxxxxxxxxx>
• Date: Tue, 03 Jan 2006 14:16:27 -0600

George Macdonald <fammacd=!SPAM^nothanks@xxxxxxxxxxxxx> wrote:

On Mon, 2 Jan 2006 18:00:53 +0000 (UTC), David Wang <foo@xxxxxxxxxxx>
wrote:

I've already defined what I meant by "full capacity". 4 ranks of DRAM devices, 18 devices per rank, 72 devices per channel running at 400 Mb/s.

As to the reference, the message header points right back in this thread,
and there's nothing in that post that shows 72 devices per channel @ 400 Mb/s.

What is this - myopia?... denial?  Rob has 2x Crucial 2GB RDIMMs on each
channel.  I'd have thought you'd be able to figure it out.  Are you even
reading what I've said?... that the reference was to a post in this
thread... or are you just shooting from the hip?

Rob has 2 2-GB RDIMMs per channel. This gets him 4 GB per channel and
8 GB per CPU.

This is the same configuration as the 32 GB per 4P Opteron box @ 400 Mb/s configuration that you believed to be limited.

I had thought that Rob's difficulty in configuring even this setup with mixed RDIMMs would go some ways in convincing you that you don't just
throw 8 GB of DDR(1) memory per channel into an Opteron box and expect it to work @ 400 Mb/s - apparently I was incorrect in expecting you see that the two configurations are equivalent.

You need them to make PC3200 4 GB RDIMMs with 36 devices and work in the 2 slot boards to get to 8 GB per channel and 16 GB per CPU. Once you have
that, then you can raise the memory capacity of the 4P Opteron box to 64 GB. Until then, the limit for the 4P Opteron box remains as 32 GB of DDR(1) @ 400 Mb/s.

Ah, it's denial.

It's simple mathematics. You stated that more DDR(1) memory can be crammed into the 4P Opteron server @ 400 Mb/s. You need 2 4-GB DIMMs with 36 1 Gb DRAM devices per DIMM to get that done.

No one running a 4P server and using it commercially will run the box with
memory system configuration that exceeds spec.

If the spec is 3-years old and the devices and assemblies have improved,
there's no reason not to.  To deliberately igniore technology progress is
perverse.

Reliability considerations trumps everything in the traditional medium/
heavy duty server segment. You don't throw parts that have not gone through
many device-years of qualification into the nearest server box.

That claim is supported by the specification of a validated, shipping system. Your argument that the server folks can run with more memory
in the memory system by pushing the configuration beyond the validated spec - does not hold water.

No pushing, or water, is required.  If mfrs want to derate AMD's specs
that's up to them.

Which means 32 GB in the 4P Opteron box is as good as it gets (for now,
until DDR2 parts arrive), and your previous assertions in regards to HP Opteron's memory capacity @ 400 Mb/s is not valid.

Every DIMM mfr is selling unbuffered boutique parts rated at PC4000/DDR500
(2.8V seems the norm) - where they get the chips from matters not...
whether it violates some enshrined, 3-year-old JEDEC document is of no
importance to the people selling or buying.

No one buys these parts to put in a 4P Opteron/Xeon server, and the
sentiment does not apply.

There you go again trying to suggest that I said something I didn't.  I
thought it seemed perfectly obvious here and in my previous mention of
those PC4000 DIMMs that the fact that such devices are available, means
that higher performing devices can be used for servers.  I'm getting tired
of repeating myself here.

The over spec'ed parts are never going to end up in a server. Power increases proportional to square of the voltage. In big servers packed with DRAM devices, you're not going to want to increase memory capacity by cranking up the voltage to get the performance, even assuming you can get such a memory system to qualify.

You derided FBD's for the power consumption of the AMB, yet somehow power increase to shoehorn overspec'ed memory into a server box is acceptable?

It's not going to happen, and your repeated reference in bringing
the overspec'ed parts into a discussion about server memory is distracting to say the least.

Heatpipes? From what I've seen, it's just a small heatsink. I think it's about ~4W per fully-on AMB, and you can selectively turn off parts of it to save power.

This
http://www.tecchannel.de/_misc/img/detailoriginal.cfm?pk=346982&fk=432957&id=il-74145445969594731
is what I'd call a heatpipe heatsink and it is *not* small in relation to
the part.  Other sources have commented on the heat problem and people
don't normally put fans over devices which are not hot - you'll need to do
more than think... like maybe burn your finger on the thing.

"Heatpipe" has specific connectation, and it does not apply here. That is a small clip on heatsink.

The reason that fan is there is because the MB is sitting out in the open,
and there's no airflow over the AMB. In a real system, air would flow over
the FBD's. You can see in the picture that the FBD's are aligned with the
direction of the heatsink fins on the CPU.

.

• Follow-Ups:
  • Re: 4-way Opteron vs. Xeon-IBM X3 architecture
    • From: David Wang

• References:
  • Re: 4-way Opteron vs. Xeon-IBM X3 architecture
    • From: George Macdonald
  • Re: 4-way Opteron vs. Xeon-IBM X3 architecture
    • From: David Wang
  • Re: 4-way Opteron vs. Xeon-IBM X3 architecture
    • From: George Macdonald
  • Re: 4-way Opteron vs. Xeon-IBM X3 architecture
    • From: David Wang

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