News for hackers. Stuff that matters.
Re:Details on AMD's Quirky Chipset Solutions for AM5 by wmf on Sunday May 22, 2022 @06:12PM (#31473326)
Won’t the timing of each chipset on each board need to be painstakingly individually configured to avoid latency from a “default” profile used in all chips (which inherently vary between every batch)?

No, because PCIe works completely differently from RAM. PCIe is a packet-based protocol that's very latency-tolerant. (Multi-lane PCIe links may require deskew but that's a standard feature that has existed all along.) I think it was Marcan who tunneled PCIe over RS-232 and the chips didn't even notice.

Re:Details on AMD's Quirky Chipset Solutions for AM5 by zamalek on Sunday May 22, 2022 @07:41PM (#31473926)
This isn't really true for PCIe 4 and beyond. For example, if you use a competently manufactured PCIe 3 riser in a PCIe 4 GPU configuration then VGA will fail to POST more times than it succeeds (on the order of successfully booting 1/10), if it POSTs at all. Given how expensive PCIe 4 risers are most people choose to downgrade to PCIe 3 in the firmware settings.
Re:Details on AMD's Quirky Chipset Solutions for AM5 by AlphaSite on Sunday May 22, 2022 @08:50PM (#31474305)
Are you sure this isn’t because of the tightened electrical tolerances for PCIe’s physical layer, not the protocol it’s self?
Re:Details on AMD's Quirky Chipset Solutions for AM5 by wmf on Sunday May 22, 2022 @08:34PM (#31474221)
That's signal integrity not latency though.
Re:Details on AMD's Quirky Chipset Solutions for AM5 by cududa on Sunday May 22, 2022 @06:46PM (#31473553)
Well the chipset also handles shuttling RAM channels..
Re:Details on AMD's Quirky Chipset Solutions for AM5 by NinjaKitten on Sunday May 22, 2022 @07:18PM (#31473778)
No. You appear to have a fundamentally flawed understanding of the system at hand.
Re:Details on AMD's Quirky Chipset Solutions for AM5 by cududa on Sunday May 22, 2022 @07:26PM (#31473836)
Perhaps. 16 years out from AMD ram/ cpu channel optimization. If the chipset isn’t handling RAM channels what component is?
Re:Details on AMD's Quirky Chipset Solutions for AM5 by wtallis on Sunday May 22, 2022 @07:31PM (#31473858)
The DRAM controller has been on the CPU socket since AMD's Opteron/Athlon 64 (2003) and Intel's Nehalem first-gen Core i5/i7 products (2008). AMD's recent migration toward multiple chiplets on the CPU package has not changed the direct connection between DRAM and the CPU socket.
Re:Details on AMD's Quirky Chipset Solutions for AM5 by Laforet on Sunday May 22, 2022 @07:54PM (#31474019)
>AMD's recent migration toward multiple chiplets on the CPU package has not changed the direct connection between DRAM and the CPU socket

This is true. However with the MCH off-chip and worst case inter core latency comparable a DRAM refresh cycle, AMD could in theory move the MCH away from the socket and see no major performance penalty.

Not to mention the Zen 2 IO die is just a cut-down version of X570, or maybe it is the other way around heh?