4 ms·
PCIe 7 = 128 GT/s = 64 Gbaud × PAM-4 = 32 "GHz" (if you alternate extremes on each symbol) for gen6, halve all numbers
by eqvinox 1y ago
PCIe 7 = 128 GT/s = 64 Gbaud × PAM-4 = 32 "GHz" (if you alternate extremes on each symbol)
for gen6, halve all numbers
- Dylan16807 1y agoIs it me or are they using the term GigaTransfers wrong? They're counting a single PAM4 pulse as two "transfers".
- eqvinox 1y agoThey kinda are and kinda aren't, they're just using their own definition… (I'm accepting it because "Transfers"/"T" as unit is quite rare outside of PCIe)
- zamalek 1y agoGT/s is also gaining ground for system RAM in order to clear up the ambiguity that DDR causes for end-consumers.
- Dylan16807 1y agoAnd it's a good way to remove the ambiguity of things like DDR, but ugh "transfers" is not the best word here. Looking at some documents from Micron I don't see them using GT/s anywhere. And in particular if I go look at their GDDR6X resources because those chips use PAM4, it's all about gigabits per second [per pin]. So for example 6GHz data clock, 12Gbaud, 24Gb/s/pin.
- mjevans 1y agoWould you rather go back to the modem days and call a 'Transfer' a 'Baud'? PAM encoding is already analog, and also correspondingly more expensive (power, silicon size, etc) for the increase in speed. It really wouldn't surprise me if even on workstation platforms only a subset of core lanes were Gen6+ and the common slots were redriven Gen5 or less off of a router / switch chip.
- Dylan16807 1y ago> Would you rather go back to the modem days and call a 'Transfer' a 'Baud'? We don't have to go back, baud is still in use. I would expect transfers per second to be a synonym for baud though, and for bits per second per pin to use a different word.
- wtallis 1y agoAside from GDDR for GPUs, DRAM is still mostly specified with MT/s rather than GT/s, probably because marketing prefers bigger numbers. It'll probably fall off once 5-digit numbers become commonplace.