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A comment on GigaByte CXL memory expansion card with up to 512GB DRAM.

Re:GigaByte CXL memory expansion card with up to 512GB DRAM by JonChesterfield on Saturday September 06, 2025 @06:00PM (#45153264)
I don't get it. The point of (ddrN) memory is latency. If its on the far side of pcie latency is much worse than the system memory. In what sense is this better than ssd on the far side of pcie?
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Re:GigaByte CXL memory expansion card with up to 512GB DRAM by wmf on Saturday September 06, 2025 @06:09PM (#45153336)
It's only ~2x worse latency than main memory but 100x lower than SSD.
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Re:GigaByte CXL memory expansion card with up to 512GB DRAM by JonChesterfield on Saturday September 06, 2025 @06:53PM (#45153653)
I'm finding ~50ns best case for pcie, ~10ns for system. Which is a lot closer than I expected.
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Re:GigaByte CXL memory expansion card with up to 512GB DRAM by adgjlsfhk1 on Saturday September 06, 2025 @10:24PM (#45154834)
no system ram is 10ns. That's closer to L2 cache.
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Re:GigaByte CXL memory expansion card with up to 512GB DRAM by Cr8 on Sunday September 07, 2025 @12:03AM (#45155293)
pcie devices can also do direct transfers to each other - if you have one of these and a gpu its relatively quick to move data between them without bouncing through main ram
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