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What's going on with this 128GB number? What's the actual limit here? I thought we had 40 bits of physical memory to work with.
by thrownaway2424 11y ago
What's going on with this 128GB number? What's the actual limit here? I thought we had 40 bits of physical memory to work with.
- toast0 11y agoThe board has 4 ram slots, and 32gb is generally available (64gb is still in 'soon' territory, I think). Xeon e5 v3 has four ram channels instead of two for the processors in the article, and can handle three dimms per channel (or at least the board in the article only haa two slots per channel). I assume there's some market segmentation happening here, but it's also a way to reduce board size and pin count.
- thrownaway2424 11y agoThat makes sense. I didn't realize these had so few channels. What I was concerned about was possibly baseless market segmentation engineering, in the same way that they elide ECC from the "Core" line of CPUs.
- ksec 11y agoSamsung has announced they had a 128GB Stacked DRAM ready soon. So 4 DIMM could fit 512GB Memory. So i guess the problem is with address space as mentioned above.
- Sanddancer 11y agoThe Xeon Ds have had a max of 128 gigs, or 37 bits of addressing, since they came out last year. For Skylake, they have bumped up the addressibility to 36 bits from 35 bits, which is where it had been for a number of processor generations. For the E5 Xeons, the amount of physically addressable RAM is at 46 bits, and has been for a couple generations. Intel's used addressible RAM for a while as one of their segmentation methods to push people towards their higher end if their usage is RAM heavy.
- baq 11y agoit's market segmentation, sure, but also every bit of address line that you don't use translates directly into watts wasted.