1U P4 Systems

Bari Ari Bari at onelabs.com
Mon May 21 18:23:32 PDT 2001

alvin at Mail.Linux-Consulting.com wrote:

> hi josip..
> you are right in your concerns...
> teh itty-bitty 40mm fans are barely enough to keep the 
> 1U chassis cool....even for a P3....amd and p4 requires
> lots more cooling capacity...
> amd athlon/duran require 250W power supply ??...
> Intel P3 system can get away with 150W power supply...
> larger cases ( deeper ) does NOT provide any cooling
> improvements... you have to move the air around... and
> the problem is the atx connectors in the back prevents
> air flow.... front to back...or side to side is okay too
> all of this is in 1U cases...
> we have lateral/squirl cage fans that we are considering
> for our next generation P4 based 1U chassis ... 
For one P4 on an off the shelf ATX motherboard in a 1U why not just 
replace the top of the enclosure with an aluminum extrusion with a nice 
profile for convection cooling tied to the CPU case? There is easily 
enough area in a 19" rack foorprint to cool off the 86W/per cpu for a 
few P4s.

> On Mon, 21 May 2001, Josip Loncaric wrote:
>> Steve Gaudet wrote:
>>> Based on the current P4 die won't see the P4 in anything smaller than a 2u.
>> Except for the P4/1.4 1U RackSaver link posted by Tim...  However,
>> cooling a 1U case concerns me.  The RackSaver RS-1100 claims to have 6
>> small case fans (> 40 cfm total), and a 250W ATX12V power supply.  I
>> understand the need to be space efficient, but I'd feel more confident
>> about cooling with larger cases..

We're designing very dense 8-16 CPUs per 1U clusters now. You can't do 
this with off the shelf ATX motherboards and low profile ATX power 
supplies and rely on a few weenie 1" fans for forced air cooling. There 
are a few small footprint ATX dual Socket 370 boards that will get you 4 
CPUs per 1U but they aren't cooled well since they are designed for a 
typical desktop enclosure with high profile heatsink/fan combinations 
and not a low profile 1U enclosure.

If you look at some of the latest dense servers like the Crusoe based 
systems with 24 CPUs per 3U announced recently, they use convection and 
forced air cooling since they have relatively low powered (heat & 

For dense clusters with high wattage/high performance CPUs like the P4 
you need to move the heat from the surface of the hottest components 
like the CPUs, chipsets and power supply mosfets by conduction out of 
the enclosure and then rely on forced air and convection cooling for the 
remainder of the components. If you need to get things cooler (in case 
you're cluster is going into a very warm climate) you can also add 
forced AC since the cost of a small AC unit and some sheet metal is less 
than the cost of 1 CPU. Mainboard and power supply design for cramming 
multiple CPUs and chipsets in a 1U board is pretty cut and dry. IMHO 
you're better off building your own boards and power supplies than 
trying to kludge up dense systems with components designed for the 
desktop market.

Does P4 with Rambus really make sense for clustering since SMP with 
Athlon4 or ULV PIII with DDR is lower priced and produce far less heat 
along with the high MFLOPS? SMP with IA-64 will also be available soon 
to add to the choices.

Bari Ari                 email: bari at onelabs.com

O.N.E. Technologies
1505 Old Deerfield Road        tel: 773-252-9607
Highland Park, IL 60035        fax: 773-252-9604


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