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3x1GB RAM outperforms 4x1GB on Win XP 32-bit?
We have a Dell T3500 user that must use Windows XP, 32-bit, to run a specialized, resource hungry application, E-Prime. Periodically the computer locks up. It has 3GB of RAM so we looked into adding another 1GB. I understand 4GB of RAM is the limit for a 32-bit operating system, and at least part of it would be used to map video card memory, 256MB in this case. However local IT resources have stated the T3500 “… uses triple-channel memory, in which a 3x1GB RAM configuration will outperform a 4x1GB one.”
This seems odd since adding RAM usually enhances performance. Is the drop in performance for 4GB RAM system vs. a 3GB RAM system significant? Even without the use of the full 4 GB of RAM could we see some greater stability and fewer lock-ups?
theflash1932
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February 6th, 2012 11:00
It's not so odd, considering that XP 32-bit on that machine probably won't have much more than 3.25GB of usable RAM (due to hardware management), meaning that upgrading from 3GB to 4GB would only give you 250MB of extra RAM as an upgrade. In triple channel memory configurations, the processor can communicate corresponding and complimentary data to all three memory channels at once. In a dual channel configuration (4x1GB), only two channels (each with two DIMM's) are used for data flow. The extra bandwidth in a triple channel configuration, in my opinion, would be far more valuable than a .25GB increase in available RAM. Run some benchmarks to compare.
jackshack
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February 6th, 2012 11:00
I can't speak directly to the T3500 since I know little about it, but the difficulty with the fourth GB of memory on a 32 bit OS of any type is that it will not use that extra memory. Four Gigabytes is the maximum address space of a 32 bit system, and that fourth GB is occupied by I/O ports, video RAM, and other special things needed by the computer in order to work. The maximum memory normally seen by a 32 bit OS is about 3.25 GB. Any RAM installed above that address will not be used.
info_Please
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February 21st, 2012 10:00
A benchmark is what I am looking for. Since Microsoft's recommends 128 MB of RAM for XP, my thinking is that the 250 MB gained by taking the total RAM up to 4GB might be just the advantage needed to keep the computer from looking up while using resource hungry applications. Given the confidence of those who stated 3GB of RAM outperforms 4GB of RAM I thought a benchmark must already exist. So far I have been unable to find one. Ideally before I throw hardware at the problem I want to fully understand the trade-offs.
jackshack
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February 21st, 2012 13:00
So far as I know, it is more a matter of economics than performance. I don't know about other operating systems, but Windows XP 32 bit divides its 4 GB of address space into 2 GB for applications and 2 GB for operating system, I/O, and video memory use. There is a switch as I recall that one can place in one of the start-up files that tells Windows to allow sharing the third GB with applications. Unfortunately, when this switch is used, Windows gets slowed down as it needs to parcel out what part of the third GB gets handed to one or more applications and how much it uses for itself. If that setting is not used it really makes no difference if you install 4 GB or 3 GB; the first 2 GB go to the applications and Windows does whatever it needs to do with the the 3rd GB. If you can get a deal on a pair of 2 GB memory modules, by all means do so. Windows won't use most of the 4th GB, but other than being bothersome to one's sense of efficiency, the computer will work just fine.