time to buy Mac Pro - 4GB or 6GB?

[kudukudu]

There have been several good articles around configuring memory on the Mac Pro such as this:

http://www.diglloyd.com/bike/free/MacPro/memory.html

The consensus seems to be that performance is best using 4 sticks of memory of the same size to maximize memory bandwidth and minimize latency (e.g. 4 x 1, 4 x 2, etc.).

I am going to order the new Mac Pro with the default 2 x 1 GB configuration. My question is whether I should order 2 x 1 or 2 x 2 from a third party to bring it to either 4 GB or 6 GB. I will be using this machine for home and will likely have the following applications open on a regular basis:

PS3, lightroom, safari, firefox, mail, MS word, itunes

I will also use the machine for some light video editing and will likely run parallels or something like that for windows XP. I will also run bootcamp with Windows XP for some light gaming.

I am concerned whether I will take a performance hit with mismatched memory (2 x 1, 2 x 2) and my gut sense is that 4 GB should be enough, but I cannot stand page-outs. Should I just bite the bullet and get 6 GB?

[speakerwizard]

i always thought the geeks 'rule of thumb' is a gb per cpu (core)

[kudukudu]

I was thinking of getting the single quad core CPU version of the mac pro so maybe 4 x 1 is the way to go.

[hugodrax]

8GB

4 sticks of two. Silly to buy 6GB.

I been running without a reboot for 30 days(last boot was to play a game in bootcamp), **** load of apps running even my wifes Virtual XP desktop running in her own usersession.

Worth the investment since you will have the snappy even with a ton of apps open and never closing them. I have all 4 spaces allocated with stuff.

[CanadaRAM]

Yes, I agree 4 x 2 Gb is the optimum configuration.
Don't go and buy a bunch of 1 Gb's
Even if you can afford only 4 Gb, get 2 x 2, leaving the door open for another 2 x 2 later.
Avoid installing in the 3 and 4 sockets, they are slower than the 1 and 2 sockets.

[Weepul]

I too was thinking about getting 2x2GB modules to add to Apple's 2x1. 8GB seems like more than I'd use, and 4GB isn't as much of an increase (from my 2.5GB) as I'd like for a new machine. So I'm echoing the OP's question; what's the performance hit like from 4x1 vs. 2x1 and 2x2?

As an aside, what do you do with the 2x1 that comes with the Mac Pro if you go for 4x2?

[Firefly2002]

You don't really do anything with it.. you let it sit on your desk. Maybe you sell it. I don't see any reason not to get "only" 4GB though. Do you really need that much? That way I guess you could buy only 2x1GB instead of a lot more for 4x2. The more memory you have, the slower your computer is due to higher latencies (unless, of course, you need more memory and are hitting the hard drive, then it's the opposite).

Also... as I understand it, quad-channel increases max bandwidth, but actually increases latency. FB-DIMMs are really a bad idea.. I'm not sure why Apple's using them. They're just slow.

[kudukudu]

Thanks for the recommendations on RAM. I ended up going for 8 GB from OCW (4 x 2 GB) and agree that 8 GB is a definite sweetspot for the MP. Allocating 2 GB to Windows XP via Fusion still leaves me enough room to run Lightroom, itunes, firefox, etc. without having to worry about page outs. I haven't installed Photoshop yet, but I can see that 4 GB definitely would not have been enough.

I have the original 2 GB from Apple sitting in a box. I figure that I'll benefit more from lower latencies having the ideal 4 sticks of RAM than with the small amount of incremental benefit I'd get by bumping the system up to 10 GB.

I was thinking of selling my original 2 GB, but if I ever need to return the machine to apple I figure I better have these lying around.