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Beatrice October 3, 2002 04:56

which processor for fluent6 on a biprocessor
I want to buy a bi-processor for running fluent 6 with 2 Go RAM minimum. I want to know if someone have some ideas on type of processors to use (AMD Athlon 2000+ or intel Pentium 4) and also the motherboard, memory type....


lohen October 3, 2002 05:00

Re: which processor for fluent6 on a biprocessor
Hi, So I get a PC at the beginning of the year 2002, it's Bipro with 2 AMD 1.2 GHZ, Now it's better Athlon 2000+, look on internet, in Surcouf or other salor. c'est clair avec un bipro, ca tourne bcp mieux, 2 Go de ram c'est bien. au niveau des marques de carte mère : MSI, Matsonic, ASUS ... Voila Ciao

Piran October 3, 2002 05:25

Re: which processor for fluent6 on a biprocessor
I have a dual Athlon 1800MP+ and it runs very smoothly. If you choose a dual Pentium it will cost you probably a whole lot more (when I bought it at the beginning of this year a comparable Intel machine costed the double, I don't know what the difference is now). If you only look at the performance an Intel with RIMM memory is the choice, if you look at the price then the AMD wins. If you can wait for a few months you could buy the new AMD Opteron processors: double the amount of L2 cache memory, higher clock-speeds and 64bit! Fluent normally releases a 64bit version for Linux Redhat in November, so the 2 combined should give you impressive performance. And if you want to you can go up to 8 processors! Also pay attention to the data-storage: a RAID array of HD's will also give you a performance boost if you write a lot of data during your simulations (monitor lines, hardcopy's...)

Jonas Larsson October 4, 2002 03:22

Re: which processor for fluent6 on a biprocessor
I would buy a P4 with 1066 RDRAM memory (RDRAM memory still beats the best DDR RAM option and this is very important for most CFD codes)

Scott Whitney October 7, 2002 11:37

Re: which processor for fluent6 on a biprocessor
Look through Fluent's benchmarks at:

Fluent doesn't have quite enough information (such as type of memory used) but those benchmarks still give a general picture of AMD vs Intel speeds. The most easily compared chips would be the AMD 2000+ MP and the Intel 2.0 GHz Xeon both running Linux. From the benchmarks above, the Intel chip won in all of the simulations, but the speed difference was usually under 10%.

The 2000+ MP and 2.0 GHz Xeon are both older chips. The fastest selling AMD dual processor chip is the 2200+ MP, about 10% faster than the 2000+ MP. So according to the benchmarks above, this should be very competitive with the 2.0 GHz Xeon. Pricewise the 2200+ MP and the 2.0 GHz Xeon are both $215 so they give nearly equal performance/price ratios. Note: this is processor price only, I'll discuss the rest of the system below.

Intel's fastest dual processor chip is the 2.8 GHz Xeon. This should be a good 35% to 40% faster than either the 2.0 GHz Xeon or the 2200+ MP.

Unfortunately you have to pay for this speed. Current dual processor Intel motherboards are $300 more than AMD dual processor motherboards (although cheaper ones are rumored to be coming out this fall). Each 2.8 GHz Xeon is $400 more than the 2200+ MP or 2.0 GHz Xeon. Memory prices are also going to be higher - expect to pay $500 more for an Intel system's memory if you truely need 2 GB of memory. So to get the 35% speed boost over the AMD 2200+ MP, you'd have to pay $300 + $500 + 2*$400 = $1600 more for the computer.

Compared to the price for employee time, and price for Fluent license, this $1600 is probably negligible. So if this 35% speed boost will mean you use less employee time or you can do more simulations per Fluent license, I'd go the Intel route. If not, then maybe you don't need a computer that is that fast. Maybe a dual 2.4 GHz Xeon will suffice, saving you $800.

Prices listed here are from, if you buy from an OEM like Dell for example, prices may vary drastically. Note: if you do go the Dell route, buy during a 8X memory for free week and you'll save a bundle.

Scott Whitney October 7, 2002 11:50

Re: which processor for fluent6 on a biprocessor
Some thoughts on Piran's post:

1) The single processor version of the Opteron has been pushed back to Feb/Mar of 2003. The dual processor version of the Opteron hasn't been given a definate date, but likely will be a couple months later. I think half a year is far too long to wait. 2) Opteron prices will be exceedingly high in many people's opinions. Don't expect AMD to keep their $200 prices on this chip. I think the consensus is that it will cost $500-$700 per chip at its release. Intel's Xeons range from $200 to $615. 3) No one knows what the Opteron's clock speed will be. Very likely it will be between 1.8 GHz and 2.0 GHz to start with. By mid 2003 both the AMD MP and the Intel Xeon will be faster in clock speed and faster in overall performance. 4) The 8 processor capability isn't supposed to be here until late 2003. Plus the cost of 8 Fluent licenses must be quite high. I'm not sure that this will be a good fit for Beatrice asking about a dual processor computer.

5) In my experience, most iterations take far longer than saving the data after the iterations. In fact, I've never seen saving data exceed 10% of the time the iteration took. IDE RAID is a complete waste, and I can show benchmarks to back that up. So that means to get decent RAID you need SCSI which will likely add over $1000 to the price of the computer (for the SCSI controller and several SCSI drives). That amount of money for a small speed boost seems funny from someone who is conserned about price.

Piran October 7, 2002 14:54

Re: which processor for fluent6 on a biprocessor
Thanks for your thoughts! You definetly got a point in them. A few remarks though:

1) I already stated that if you want top-performance you'll have to choose Intel (Xeon 2.8GHz). But if you have to look at the price AMD is the winner. As you demonstrated yourself in your other posting an Intel based system (Xeon 2.0GHz) comparable to an AMD based one (MP 2200+)will be $800 more expensive. To have the same performance that is a lot.

2) I only mentioned the Opteron as a possibility. As you stated, we know too little about it right now to pass a verdict. We don't know when it will come out and we don't know how much it will cost. The argument of the lower clock speed does not matter that much. Clock speed isn't everything, architecture is more important (An Intel PIV gives less performance than an Intel PIII or an AMD AthlonXP for the same clock speed; or compare to other cpu's as Alpha). In this case the performance boost will rather come from the 64-bit Fluent code and the larger L2 cache. We will have to see.

3) IDE RAID definetly has its benefits. I have simulations to back it up. As I said it's only important when you have to store a LOT of data. I have run simulations where writing the data took 40% of the overal simulation time!!! Those are exceptional, I admit. But when I run more conventional simulations (still with a lot of monitor lines) on a system with IDE RAID it's up to 10-15% faster than without RAID. But if you don't write a lot of data, of course, you won't see a lot of difference. Most advanced mobo's come with an on-board RAID controller: it only costs you the price of an extra HD, and you get double the amount of storage place. That's not a lot, is it? SCSI: definetly too expensive.

It's often dangerous to have this kind of discussions. They usually end in a pro-AMD vs pro-Intel back-and-forth discussion. Bottom line: your budget decides everything and you have to try to get the best performance for your money.

Jimmy October 9, 2002 08:56

Re: which processor for fluent6 on a biprocessor
Ici on utilise des Bi-P4 xeon 1.8GHz avec 3-4 Go de RDram (800MHz), ça marche pas mal mais ça dépend surtout de ce que tu veux en faire. Typiquement avec cette machine, un calcul LES sur 2.000.000 mailles sans reaction chimique, c'est environ 15 jours de calcul pour faire 1000 pas de temps (ce qui est un peu leger pour faire des statistiques d'ordre élevé).

à titre indicatif : prix de la machine, pas loin de 50.000ff

pour des calculs Rans, un bi p4 classique ou un bi XP peut convenir sans problèmes (entre 10 et 15000 ff). Il faut surtout prendre des disques SCSI sans ça le temps perdu en swap sera insurmontable.

Apres si l'argent n'est pas un problème on peut envisager des Itanium 64 intel,....

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