Memory bandwidth still critical.


macrumors 6502a
Original poster
Jul 15, 2007
Will the new chipsets increase the memory bandwidth? Right now the Mac Pro will do 21Gb/s but more cores will need more GB/s maybe 42Gb/s To really take advantage of large workloads you need more bandwidth to your memory once you increase the core counts. 21Gb/s is fine for 4 cores but at some point
Intel will need to work on the memory side of the house.

This is one of the things that made Crays so much powerful compared to PCs back then with measly memory bandwidth. I would laugh when people would say wow look my PII does 300mflops. And I would run the equivilant cray job on that PII and it would choke on the workload compared to the Cray EL.

I would have to say just recently last 1 1/2 years have PC's finally caught up to the memory performance of the supers of the mid 1980s and 90s.

ie: Mac Pro could do Cray C90 series workloads for example


macrumors regular
Jan 29, 2004
There are memory improvements with the next chipset, I'll leave it up to you to google the specifics.

However, current and the next round of Xeon systems will still be bottlenecked by the FBDIMM memory, which is inherently more latent then other options. This is due to the serialization step that must be performed.

FBDIMM's are a dying tech, I've spoken to apple engineers on this issue and they are aware of it...but of course, the ball is in intel's court.


macrumors member
Aug 10, 2007
I'd love to have more than 3 gigs in this MBP, but the 2.33's topped out at 3. When I buy my MP in few weeks (fingers crossed), we'll be talking about a bit more than 3 gigs. BTW, based on current speculation as to mobo/chipset, what memory chips will the next gen MP's use? Just wondering if I should start stocking up now or wait until I get the box.
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