Windi
2019-06-19, 15:40:17
Ich wollte damit jetzt nicht wieder die anderen Themen voll spamen.
Bei den ganzen News über PCIe6 bin ich zufälig über einen etwas älteren Artikel gestolpert.
https://www.eetasia.com/news/article/18061502-pcie-45-higher-bandwidth-but-at-what-cost
The big tradeoff of the higher speeds is that signals won’t travel as far on existing designs. In the days of PCIe 1.0, the spec sent signals as much as 20 inches over traces in mainstream FR4 boards, even passing through two connectors. The fast 4.0 signals will peter out before they travel a foot without going over any connectors.
Anscheinend werden die Probleme mit der Signalqualität durch die Leitungslängen und den Steckverbindungen immer größer.
Arnaud Schleich thinks that the situation is even worse. PCIe 4.0 signals are only travelling three to five inches, said the CEO of PLDA Inc., a designer of PCIe controller cores that came out with 4.0 products three years ago.
Die möglichen Leitungslängen haben sich mehr als halbiert.
Retimer chips for a full 16-lane full PCIe 4.0 could cost $15 to $25 — if you can find them. Upgrading an adapter card from Megtron-2 to Megtron-4 materials might only add a dollar or so. However, the cost of a similar upgrade for a motherboard is about $100, and if the upgrade is to even higher quality Megtron-6 it would cost about $300.
“The data center will go to Megtron-4 for PCIe 4.0 and that will add maybe $10 cost — and you may still need retimers,” said Krause. “For version 5.0, people will weigh even higher-cost PCB materials and retimers or move to cables.”
Man kann viele Probleme ja mit Geld erschlagen, Consumer-Boards können aber nicht einfach beliebig teuer werden. Bei PCIe4 sollte es gerade noch reichen da GPU-Slot, erster M.2-Slot und der Chipsatz recht nah an der CPU liegen. Wer mehr will braucht dann teurere Mainboards mit Retimern. Ab PCIe5 könnte es aber extrem brenzlich werden.
“What we have been using for 4.0 and expect to use for 5.0 is twinax cables and firefly connectors,” he added. “The cost is very low compared to retimers, you can get whatever you want in distance, and the latency is really good.”
Indeed, Krause noted that “there’s been a lot of interest in using cables … for every inch on a board, you can go 10 inches on cables for the same power and loss budget, but cables have costs in being routed and connected.”
Vieleicht binden wir in Zukunft unsere Karten per Kabel an?
An even bigger shift that engineers are discussing is to new mechanical designs. The industry has thrived for nearly 18 years on the PCIe mechanicals, but some say that it’s time for a change.
A shift would be slow and painful given the market of hundreds of PCIe cards and millions of sockets. The GenZ interconnect group is already exploring new designs that put a connector 60 mm closer to a processor.
“You can recover 4-dB loss at 16 GT/s and 8 dB at 32 GT/s — that can make the difference,” said Krause.
“We’re just starting education on new form factors and new connectors. I would expect a lot of people to stick with what they know and pay the cost of new PCB materials and retimers. I don’t think anyone will change mechanicals quickly, but PCIe Gen 4 or Gen 5 could be the intercept point for some designs.”
Oder es wird doch weiterhin auf den Erweiterungsslot gesetzt. Dann aber mechanisch überarbeitet und nicht mehr mit den alten Karten kompatibel.
PCI Express 4.0 wird ja jetzt von AMD flächenddeckend eingeführt. Das geht anscheinend noch, ohne das die Kosten zu sehr explodieren.
Mit PCIe5/6 müsste etwas neues kommen. Ansonsten werden die Probleme viel zu groß.
Bei den ganzen News über PCIe6 bin ich zufälig über einen etwas älteren Artikel gestolpert.
https://www.eetasia.com/news/article/18061502-pcie-45-higher-bandwidth-but-at-what-cost
The big tradeoff of the higher speeds is that signals won’t travel as far on existing designs. In the days of PCIe 1.0, the spec sent signals as much as 20 inches over traces in mainstream FR4 boards, even passing through two connectors. The fast 4.0 signals will peter out before they travel a foot without going over any connectors.
Anscheinend werden die Probleme mit der Signalqualität durch die Leitungslängen und den Steckverbindungen immer größer.
Arnaud Schleich thinks that the situation is even worse. PCIe 4.0 signals are only travelling three to five inches, said the CEO of PLDA Inc., a designer of PCIe controller cores that came out with 4.0 products three years ago.
Die möglichen Leitungslängen haben sich mehr als halbiert.
Retimer chips for a full 16-lane full PCIe 4.0 could cost $15 to $25 — if you can find them. Upgrading an adapter card from Megtron-2 to Megtron-4 materials might only add a dollar or so. However, the cost of a similar upgrade for a motherboard is about $100, and if the upgrade is to even higher quality Megtron-6 it would cost about $300.
“The data center will go to Megtron-4 for PCIe 4.0 and that will add maybe $10 cost — and you may still need retimers,” said Krause. “For version 5.0, people will weigh even higher-cost PCB materials and retimers or move to cables.”
Man kann viele Probleme ja mit Geld erschlagen, Consumer-Boards können aber nicht einfach beliebig teuer werden. Bei PCIe4 sollte es gerade noch reichen da GPU-Slot, erster M.2-Slot und der Chipsatz recht nah an der CPU liegen. Wer mehr will braucht dann teurere Mainboards mit Retimern. Ab PCIe5 könnte es aber extrem brenzlich werden.
“What we have been using for 4.0 and expect to use for 5.0 is twinax cables and firefly connectors,” he added. “The cost is very low compared to retimers, you can get whatever you want in distance, and the latency is really good.”
Indeed, Krause noted that “there’s been a lot of interest in using cables … for every inch on a board, you can go 10 inches on cables for the same power and loss budget, but cables have costs in being routed and connected.”
Vieleicht binden wir in Zukunft unsere Karten per Kabel an?
An even bigger shift that engineers are discussing is to new mechanical designs. The industry has thrived for nearly 18 years on the PCIe mechanicals, but some say that it’s time for a change.
A shift would be slow and painful given the market of hundreds of PCIe cards and millions of sockets. The GenZ interconnect group is already exploring new designs that put a connector 60 mm closer to a processor.
“You can recover 4-dB loss at 16 GT/s and 8 dB at 32 GT/s — that can make the difference,” said Krause.
“We’re just starting education on new form factors and new connectors. I would expect a lot of people to stick with what they know and pay the cost of new PCB materials and retimers. I don’t think anyone will change mechanicals quickly, but PCIe Gen 4 or Gen 5 could be the intercept point for some designs.”
Oder es wird doch weiterhin auf den Erweiterungsslot gesetzt. Dann aber mechanisch überarbeitet und nicht mehr mit den alten Karten kompatibel.
PCI Express 4.0 wird ja jetzt von AMD flächenddeckend eingeführt. Das geht anscheinend noch, ohne das die Kosten zu sehr explodieren.
Mit PCIe5/6 müsste etwas neues kommen. Ansonsten werden die Probleme viel zu groß.