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I am upgrading the memory on a Dell PowerEdge 1800 Server running Windows Server 2000 (32 bit). My Computer -> Properties currently reports 2,096,432 KB RAM (4 modules @ 512MB each).

Crucial.com scan reports:
"Each memory slot can hold DDR2 PC2-5300 with a maximum of 2GB per slot.

Maximum Memory Capacity:  12288MB
Currently Installed Memory:  2GB
Available Memory Slots:  2
Total Memory Slots:  6
Dual Channel Support:   No
CPU Manufacturer:  GenuineIntel
CPU Family:  Intel(R) Xeon(TM) CPU 2.80GHz Model 4, Stepping 1
CPU Speed:  2793 MHz
Installed in pairs of modules."

We will be completely replacing the old 512 MB modules.
Will there be any performance difference between installing 4 modules @ 1GB vs. 2 modules @ 2GB?

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2 Answers

up vote 2 down vote accepted

There shouldn't be any measurable performance difference.

The reason that 2x2GB costs more than 4x1GB is that there is an implied value in buying bigger DIMMs, in that you are less likely to have to throw the bigger DIMMs away if/when you go to increase memory again.

If you are using Windows 2000 Server Standard, the maximum addressable memory is 4GB, and there's no way to go beyond that and you might as well just buy the 2x1GB -- leaving the 4x512MB in the server (unless there is a compelling reason to throw it away, in which case you'd buy 4x1GB).

If you have Advanced Server or Enterprise Server, the addressable memory is higher (8GB and 32GB respectively). If you think it possible that you will want to add memory again, then buying the 2x2GB is good value -- especially since you can leave 4x512MB in the board and have 6GB in the server initially.

(PS: Memory limits for 32-bit Windows 2000 versions)

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Thanks! Crucial reports that the maximum per slot is 2GB. So I'll go with the 2x2GB. (I'd upvote but I don't have the rep). –  David Murdoch May 21 '10 at 16:01
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@David: It also costs more to make denser DIMMS and you have higher reject rates at the manufacture level. –  Zypher May 21 '10 at 18:25
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Whilst there may not be an easily measured performance difference there will be some difference between options. The reason is that if you put 4x1 in then you have to use slots very slightly further away from the CPU/s and this can reduce memory speed and increase the chance of memory bus contention when compared to the 2x2 option. This effect is very clear in newer QPI-equipped servers where the whole memory bus slows down as you fill out the slots away from the CPU (from 1333 to 1066 down to 800 in some systems in fact). This issue can be confused if you're mixing ranks but all these parts (from Crucial anyway) are single rank, so that's not a worry for you today. Oh and by using the 4x1 option you also double the likelihood of contact-derived errors.

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