The Mac Pro computer has two memory riser cards with a total of 8 memory slots. On each
card, the slots are arranged as two banks of two slots each...Additional DIMMs can be installed in the open DIMM slots, as illustrated below.
DIMMs must be installed in pairs of equal size from the same vendor. In the illustration below,
DIMMs in one colored pair do not need to match DIMMs in a different colored pair.
I'd think they'd mention if installing the RAM wrong loses you half of the advertised memory bandwidth.
EDIT: I read some in the Apple Mac Pro discussions, and one of the smarter (and higher-posting) users said this:
Quote:
Yes you get a 256-bit memory bandwith with this configuration although only for the first 2GB (1GB from Riser A and 1GB from Riser of memory usage/saturation. When you go past 2GB memory usage/saturation the additional memory is only available from Riser A and hence, is only available to you at 128-bit. This ONLY affects memory saturation above 2GB to your maximum 3GB.
While that's not official, it makes sense, and there are a good number of people who believe the same thing, and no Apple guy has corrected him.
But when you get back to 8 balanced DIMMs you get your full bandwidth back over all the DIMMs.
Huh? You only need four DIMMs to max out the memory performance of the system. And ideally you want that anyway because the upper pair of slots on each riser card have higher latency than the lower pair because the slots are chained. If this time around you buy 4x 1GB DIMMs and next time you buy 4x 2GB DIMMs, then you want to put the 2GB DIMMs in the lower slots.
Quote:
To the OP's question - go for the 4 1GB DIMMs. Then if you want more in the future you won't have to waste the 512's you are replacing.
Reselling computer components is virtually invariably a loss of money.
Especially with something like this. Most FB-DIMMs are in high-end Intel servers, and most people with high-end Intel servers don't want 512 MB sticks (since they want higher density 1 or 2 GB sticks) or wouldn't want to buy their RAM on eBay.
Especially with something like this. Most FB-DIMMs are in high-end Intel servers, and most people with high-end Intel servers don't want 512 MB sticks (since they want higher density 1 or 2 GB sticks) or wouldn't want to buy their RAM on eBay.
A likely buyer would be another Mac Pro owner, due to the heat sinks. I think there will be plenty of Mac Pros that will have empty slots that can be filled.
I've sold workstation memory on eBay just fine, pairs of 512MB ECC sticks.
That's still a slim market. It's not like selling PC RAM, where there are a lot of people looking to buy. And if I'm buying uninsured RAM, I want it cheap.
Not to mention that most Mac Pros will be owned by production houses that'll want only high quality, insured stuff. They'd rather throw away an extra $100 on the upgrade than risk it failing and having no one to turn to.
That's still a slim market. It's not like selling PC RAM, where there are a lot of people looking to buy. And if I'm buying uninsured RAM, I want it cheap.
Not to mention that most Mac Pros will be owned by production houses that'll want only high quality, insured stuff. They'd rather throw away an extra $100 on the upgrade than risk it failing and having no one to turn to.
My experience suggests otherwise. Last December, I removed excess memory from a workstation and in two separate instances, got $200 per GB of ECC RAMBUS RAM on eBay. It's not a common type of memory, and it only works in servers and workstations. I would even expect that more individuals would be using Mac Pros, heck, if this forum says anything, apparently even a few students are buying them, that's not something I would expect from the Windows workstation market.
Huh? You only need four DIMMs to max out the memory performance of the system.
4 DIMMs don't give all slots the full 256-bit bandwidth, if you have more RAM in the other unmatched slots those particular paired-DIMMs are serviced at a 128-bit channel width. The memory controller works statically via paired paired slots, not dynamically determining which physical location to place data to overcome physical address range mismatches.
Comments
Anybody know whether having different-sized sticks has much influence on it?
Yeah, if the sticks don't match exactly, quad-channel cannot work.
The Mac Pro computer has two memory riser cards with a total of 8 memory slots. On each
card, the slots are arranged as two banks of two slots each...Additional DIMMs can be installed in the open DIMM slots, as illustrated below.
DIMMs must be installed in pairs of equal size from the same vendor. In the illustration below,
DIMMs in one colored pair do not need to match DIMMs in a different colored pair.
I'd think they'd mention if installing the RAM wrong loses you half of the advertised memory bandwidth.
EDIT: I read some in the Apple Mac Pro discussions, and one of the smarter (and higher-posting) users said this:
Yes you get a 256-bit memory bandwith with this configuration although only for the first 2GB (1GB from Riser A and 1GB from Riser
While that's not official, it makes sense, and there are a good number of people who believe the same thing, and no Apple guy has corrected him.
To the OP's question - go for the 4 1GB DIMMs. Then if you want more in the future you won't have to waste the 512's you are replacing.
But when you get back to 8 balanced DIMMs you get your full bandwidth back over all the DIMMs.
Huh? You only need four DIMMs to max out the memory performance of the system. And ideally you want that anyway because the upper pair of slots on each riser card have higher latency than the lower pair because the slots are chained. If this time around you buy 4x 1GB DIMMs and next time you buy 4x 2GB DIMMs, then you want to put the 2GB DIMMs in the lower slots.
To the OP's question - go for the 4 1GB DIMMs. Then if you want more in the future you won't have to waste the 512's you are replacing.
You don't waste them, you resell them.
You don't waste them, you resell them.
Reselling computer components is virtually invariably a loss of money.
Reselling computer components is virtually invariably a loss of money.
I've done pretty well, but maybe that depends on the perspective and the component.
Reselling computer components is virtually invariably a loss of money.
Especially with something like this. Most FB-DIMMs are in high-end Intel servers, and most people with high-end Intel servers don't want 512 MB sticks (since they want higher density 1 or 2 GB sticks) or wouldn't want to buy their RAM on eBay.
Especially with something like this. Most FB-DIMMs are in high-end Intel servers, and most people with high-end Intel servers don't want 512 MB sticks (since they want higher density 1 or 2 GB sticks) or wouldn't want to buy their RAM on eBay.
A likely buyer would be another Mac Pro owner, due to the heat sinks. I think there will be plenty of Mac Pros that will have empty slots that can be filled.
I've sold workstation memory on eBay just fine, pairs of 512MB ECC sticks.
Not to mention that most Mac Pros will be owned by production houses that'll want only high quality, insured stuff. They'd rather throw away an extra $100 on the upgrade than risk it failing and having no one to turn to.
That's still a slim market. It's not like selling PC RAM, where there are a lot of people looking to buy. And if I'm buying uninsured RAM, I want it cheap.
Not to mention that most Mac Pros will be owned by production houses that'll want only high quality, insured stuff. They'd rather throw away an extra $100 on the upgrade than risk it failing and having no one to turn to.
My experience suggests otherwise. Last December, I removed excess memory from a workstation and in two separate instances, got $200 per GB of ECC RAMBUS RAM on eBay. It's not a common type of memory, and it only works in servers and workstations. I would even expect that more individuals would be using Mac Pros, heck, if this forum says anything, apparently even a few students are buying them, that's not something I would expect from the Windows workstation market.
Huh? You only need four DIMMs to max out the memory performance of the system.
4 DIMMs don't give all slots the full 256-bit bandwidth, if you have more RAM in the other unmatched slots those particular paired-DIMMs are serviced at a 128-bit channel width. The memory controller works statically via paired paired slots, not dynamically determining which physical location to place data to overcome physical address range mismatches.