Re: matching RAM in both slots
- From: dempson@xxxxxxxxxxxxx (David Empson)
- Date: Wed, 14 Mar 2007 12:25:45 +1300
Paul Fuchs <paulfuchs@porkain'tkosher.oink> wrote:
Regarding both Intel dual and G5 iMacs ( I am looking into RAM upgrades
for both models) just how big a deal is it in terms of performance to
match and balance the chips? Is it minimal, moderate, or major? For
example, what kind of performance difference could one expect if you had
two 512 MB chips versus one 1 GB chip?
It depends on exactly which model you are talking about.
For an iMac G5, it isn't an issue.
For an iMac with Intel processor, it is only an issue for one model: the
current entry level (1.83 GHz) one with Intel Integrated Graphics. This
model uses main memory for its video buffer and the extra performance
gain by matching pairs does make a noticeable difference to the
computer's performance (a few percent).
All other iMacs with Intel processors have a dedicated graphics
processor with its own RAM and they don't gain any noticeable
performance benefit from having matched RAM. There might be a fractional
improvement if they are doing a lot of I/O (e.g. lots of Firewire,
Ethernet, disk I/O, CPU and video DMA accesses at the same time) but for
normal use it wouldn't be measurable.
For the one iMac where it matters (and other Intel Mac models with
integrated graphics), there are two other issues to consider:
The benefit of having more RAM greatly outweighs the benefit of having
less RAM in a matching pair. You will get better performance by having
512M+1G rather than 512M+512M, or 256M+1G rather than 512M+512M.
For future upgrades, having 512M+512M means that you will have to
replace one or both of the 512M with a 1G to get more memory. Having 1G
now and adding 1G later will save money in the long term, if the extra
memory is required.
It is worth noting that doing a "half now, half later" pattern (1G now,
1G+1G later) might not end up with a matched pair - the two memory
modules must have identical characteristics to be able to get the few
percent speed increase from having a matched pair. The best way to
ensure this is to buy them at the same time. Even if they didn't match
you would still gain the performance benefits of having more RAM. You
might be able to sell the old 1G and buy two new 1Gs to get the most
benefit out of them.
--
David Empson
dempson@xxxxxxxxxxxxx
.
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