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Charles Crosby June 26, 2000 14:52

Speccing a super PC
Thanks to everyone who responded to my previous request for workstation suggestions. It would appear that at the moment PC-based workstations are a very good alternative to the "real" 64-bit machines like HP, Sun, SGI and DEC, in the sense that you can probably get two dual-processor PC's to do the same amount of work as a single 64-bit machine, for about half the cost. Now, such a super PC is obviously not a cheap device (typically getting towards US$ 10 000).

What I am looking for is anybody's experience of putting together such a machine (ie. it's not a web server, or file server, or 3D games monster or any of the typical applications).

First: Is there such an animal as a dual-processor 1 GHz AMD Athlon?

Second: Who markets it, or the motherboard for it?

Thirdly: What kind of RAM chip does it need?

Any advice appreciated.

PS: The ultimate would probably be something like a 16 processor Beowulf-type cluster, but I don't think I can justify the setting up time in a production environment, also licensing of a commercial CFD-code for it appears to be a bit of a problem (like buying 16 licenses!)

John C. Chien June 27, 2000 01:18

Re: Speccing a super PC
(1). A computer with 500MHZ AMD-K-6-2 is selling for 550 US dollars. Additional 128MB RAM is 110 dollars. So, for 1000 dollars you can get a 512MB RAM machine. (2). That's all you need. The speed ratio between 1GHZ and 500MHZ is at most a factor of two. I think it is fast enough. (3). The speed can only increase the "garbage production rate". As I said before, 99% of time, I am getting the wrong answers. (4). If you sit down and think, a 500MHZ machine is more than 2000 times faster than a Radio Shack computer of early 80's. It is always cheaper for those who writes his own codes.

Jonas Larsson June 28, 2000 06:32

Re: Speccing a super PC
The current Athlon is not available in multi-CPU configurations - there is no motherboard/chip-set yet which supports this as far as I know. This is one of the reasons why PC-workstation manufacturers have avoided Athlon so far. A dual-CPU motherboard is on the way though. Today you will have to buy separate machines and connect them with a fast-ethernet.

Another interesting low-budget solution now is the Duron processor just released by AMD - it has similar floating-point performance and is cheaper. The new Athlon, aka "Thunderbird", that AMD also just released has a better cache - make sure that you don't buy the "old" Athlon.

Athlon uses standard unbuffered PC-100 DIMM memory (cheap!). Make sure you get ECC memory! There is no Athlon that supports RDRAM - but that isn't a big deal since RDRAM is too expensive and not much faster.

There is more info on and

Jonas Larsson June 28, 2000 06:36

Re: Speccing a super PC
Don't buy a K-6 machine - this processor has a very bad floating-point-unit compared to PIII/Celeron/Athlon/Duron! For "office" applications it doesn't matter that much but for CFD it makes a big difference!

John C. Chien June 28, 2000 21:28

Re: Speccing a super PC
(1). I think so. (2). It is probably easier to rent the best available PC for three months, then, rent the new one again. (3). The old question is when is the best time to buy? Wait for the new one, or buy the cheaper one. (buy the best, affordable one, PC is always relatively cheap though.)

Jens Bennetsen June 29, 2000 08:27

Re: Speccing a super PC

If you should build or buy a PC computer for CFD, the Athlon processor is the one to focus on. Regardless if it is the new or old Athlon, sine at 1 GHz the different is only within 3-6%.

Comparing with some older machines like a Pentium II Xeon @ 450 MHz the (old) Ahtlon @ 1 GHz is between 2.0 - 2.6 times faster on different commercial code like: CFX, CFD2000, and Star-CD.

About the memory, it is not always better/cheaper to buy ECC Ram compared to quality sd-ram. BUT the SD-RAM should run at 133 MHz bus speed and not just 100 MHz. And the motherboard is also very important, when it comes to overall performance. (The Asus K7V with Via chipset is nice).

Hope this help.


Jens Chr. DIAS

I. Dotsikas June 29, 2000 09:40

Re: Speccing a super PC
Buy now an Athlon computer and start working. After some months, when you have difficulties with your computationaltime sell the old one (donīt wait a long time) and buy a new onw (a state of the art-computer). If you work in a company give your old computer to a beginner or a secretary. Computer is only a tool. Nothing more. Donīt waste your time with such thoughts.


John C. Chien June 29, 2000 20:12

Re: Speccing a super PC
(1). ASUSTek Computer Inc, I think, is one of the world largest PC mother board manufacture in Taiwan. (2).

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