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2008 mac pro ram config

A

aaronw1986

macrumors 68030
Original poster
Oct 31, 2006
2,622
10
Couldn't find one asking this specifically...

Currently 4X2gb modules. Thinking about adding 2X4gb. This would leave me 2 slots so I could add another 8 gb later and have a total of 24. Seems like 4x2gb and 4x4gb should be fine? Until then I would either have 16 or 18, depending if I filled the 2 slots with my 1x2gb stock ram. Guess I want to know about performance loss with not using powers of 2, and also not an even amount of matching pairs. Thanks.
 
aaronw1986 said:
That helps with installation, but not really actual use. How much is small in a "small speed benefit to installing 4 identical modules across both risers"
Click to expand...

Don't worry about any speed benefit. If you actually need more RAM, you're much, much better off actually installing 6 FB-DIMM's. If even one page is swapped to disc, any speed benefit from running in quad mode is swamped, utterly and completely.

RAM is fast, fast, fast compared to moving stuff onto and from disc. And OS X will take advantage of lots of RAM very nicely. Don't worry about a small theoretical speed gain from such-and-such a RAM configuration! Often times, real world testing in actual use just doesn't show up any difference at all.

However, if you really have no need for the extra RAM, then don't install it and stay in quad mode . . .
 
-js- said:
Don't worry about any speed benefit. If you actually need more RAM, you're much, much better off actually installing 6 FB-DIMM's. If even one page is swapped to disc, any speed benefit from running in quad mode is swamped, utterly and completely.

RAM is fast, fast, fast compared to moving stuff onto and from disc. And OS X will take advantage of lots of RAM very nicely. Don't worry about a small theoretical speed gain from such-and-such a RAM configuration! Often times, real world testing in actual use just doesn't show up any difference at all.

However, if you really have no need for the extra RAM, then don't install it and stay in quad mode . . .
Click to expand...

Thanks, this is the kind of answer I was looking for. I've just been running a program over night (for the Netflix competition) which utilizes all 8 cores, and also uses some ram apprently. After running for about 8 hours,

Swap: 337mb(512mb)
Page ins: 4,927,563
Page outs: 43,515

So I definitely need the ram. I will probably get 8gb and add the stock ram for a total of 18 to have all risers filled. Then later this gives me the option t upgrade to 24.
 
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