News PCIe at the Speed of Light: PCI-SIG Forms Optical Workgroup

[Admin]

PCI-SIG Optical Workgroup will prepare PCIe for using optical interconnects.

PCIe at the Speed of Light: PCI-SIG Forms Optical Workgroup : Read more

 

[bit_user]

This part bears repeating:

"PCI-SIG welcomes input from the industry and invites all PCI-SIG members to join the Optical Workgroup, share their expertise and help set specific workgroup goals and requirements."

No goals, requirements, or timeline. Whatever they come up with most likely won't land before PCIe 7.0. It's even more uncertain if or when it could reach desktop or laptop PCs.

 

[Kamen Rider Blade]

We still don't have "External OCuLink" yet.

 

[InvalidError]

No goals, requirements, or timeline. Whatever they come up with most likely won't land before PCIe 7.0. It's even more uncertain if or when it could reach desktop or laptop PCs.

We've reached the point where pushing more bandwidth over PCBs may no longer be economically viable. I doubt laptops will bother with faster PCIe or optical since everything is so tightly integrated and power-conscious for the most part.

For desktops though, I could imagine optical connections being handy to break systems into 2-4 major components: 1- a fully self-contained CPU module 2) a front IO module 3) a rear IO module and 4) a motherboard (optional) for desktop-style internal expansion. If you don't need internal expansion, you get the CPU, front/back IO and stop there. Want to upgrade the CPU or switch from x86 to RISC-V? Only need to swap out the CPU module.

We still don't have "External OCuLink" yet.

If copper is no longer deemed good enough for internal connections, you can stick a fork in anything external.

 

[Eximo]

400Gbps ethernet is out there. You got $300 for five meters of fiber and $1800 for two transceivers? Couldn't find any 400Gbps NICs for sale, but 200GBps ones are only $4,000!

Still, possible that optical setups will allow for PCIe 1x at 7.0 speeds at some point that isn't cost prohibitive. Got to have that 16K VR experience after all.

 

[bit_user]

We've reached the point where pushing more bandwidth over PCBs may no longer be economically viable. I doubt laptops will bother with faster PCIe or optical since everything is so tightly integrated and power-conscious for the most part.

I was going to say that the only way I see laptops using it would be for power-savings. That would depend on silicon photonics being markedly more power-efficient, though I don't know if that's feasible.

 

[InvalidError]

400Gbps ethernet is out there. You got $300 for five meters of fiber and $1800 for two transceivers? Couldn't find any 400Gbps NICs for sale, but 200GBps ones are only $4,000!

The main reason specialty fiber cables cost so much is low volume. The cable itself would likely come down to $15-20 if everyone needed some for everything. For Tbps-scale optical PCIe, we'd likely be talking on-package photonics to eliminate in-between interfaces. No NIC, no PCIe between the CPU and NIC, no transceiver to plug into the NIC, the SoC talks whatever the on-package bus might be straight to the optical MAC-PHY stack. How cheap the interface may get would be entirely dependent on how expensive the PHY might be.

I was going to say that the only way I see laptops using it would be for power-savings. That would depend on silicon photonics being markedly more power-efficient, though I don't know if that's feasible.

How much stuff in a laptop or even a desktop genuinely requires more bandwidth than 4.0x16? Not really anything at the moment for a remotely normal person, the GPUs that might gain the most from it only have an x8 or worse interface. As an SI, would you shoulder all of the risks and additional manufacturing considerations that would come with handling CPU, GPU and IO chips that have glass fiber pigtails attached while assembling a laptop and having to splice those together afterward to save maybe 2W vs 5.0x4 on copper? I know I'd rather have a plug-in SSD which I can easily move elsewhere for data recovery, backup or replacement if necessary and no amount of power savings would make me give up on that. You could slap connectors on those pigtails, though I'd be worried about optical connectors slim enough to go in slim form factors that may require special tools to disconnect without breaking something.

On desktop, at least you have plenty of room to package major components in such a way as to give them SC/LC/whatever connectors with loops of slack inside for strain relief or repair.