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?
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)? Yes, yes they would.
Unless you had an automated solution. And if you have an automated way you could optimize CPU and DDR timing instead of using “buffered”/ “safe” latency settings to accommodate any manufacturing variance.
Well turns out AMD has a method for that. And given the necessity for a tech like this to make daisy chained chipsets work, it would seem this isn’t an idle patent. AM5 systems are basically going to get a 10-20% performance bump due to that optimization. Which is wild.
https://www.tomshardware.com/news/amd-patents-automatic-memo...