Hi all,

Can some one please tell me the memory limit for a Pentium 4 processor. Example, if I buy a COMPAQ PC or equivalent with 40++ GB HHD, can I just "stuff" in RAM. But.. up to what limit??. The supposedly experts (computer vendors) are giving me conflicting answers??

Robin said that we can get some information in the CFX Community forum, I have gone there but it is a nightmare to get information from that site. The SEARCH could NOT help me either.

Thanks, Eldoret

The max memory limit for P4 is 2 gigabyte using unbuffered memory and 4 gigabyte (3.5 gigabyte effectively) using registered memory.

Current AMD Opteron processor based PCs can have up to 16 gigabyte using registered memory, an this is far better than Xeon with its kludgy pages of only 4 gigabyte.

Thanks J.P.

What is the difference b/w buffered and registered memory ?

Hi Eldoret,

There is a separate seach function for the Forum. If you search for memory, you will find a posting under the CFX-5 Solver forum titled "Choosing a new Platform".

Regards, Robin

If you want to know the difference between unbuffered and registered memory, then I suggest you read this: http://www.lostcircuits.com/memory/reg_ddr/2.shtml

hi eldoret

The "supposedly" experts may very well be giving conflicting answers - but they may also be right. The max amount of RAM depends on which motherboard you buy - often this is is simply determined by the number of DIMM slots on the board. However, these days you can buy 1Gb DIMMs, and some of the older boards may give trouble if you stick 4 Gb into them.

You should look to your budget to determine what to buy. If you are going to use only one PC, buy a dual AMD box with 2Gb of RAM. (much as was suggested in the earlier posts). You can very well stick 4Gb on a motherboard, but might have to wait a VERY long time for a single CPU to solve such a big case. (if money is no object, buy a dual Opteron, or dual Xeon box with max RAM, and SCSI harddrives)

good luck

Hi mystic, Thanks for the useful information. After considering all variables (economics, numerics etc), I have now settled for 2 GB RAM for a single PC.

Regards Eldoret

Personal Experience:

Dell Precision 650 Dual P4 system with 4Gb of memory (installed). The machine, only recognized about 3.8Gb. 200 Mb were "lost" from the addressible RAM. Dell claims this is a known phenomena.

Running 2000 Pro: Processes are limited to 2Gb. This means a serial run can't access the full 4Gb (or 3.8Gb as the case may be). However, with a dual P4 you can run the problem in parallel and access ALL the memory.

Linux: Switched over to Red Hat 7.3 and now a single process can access the full memory (still only 3.8Gb available). Guess what? The same identical problem ran about 5% faster on W2K than on Linux.

My $0.02.

Jeff