PCIe 3.0 is barely here and rumblings of PCIe 4.0 is coming through the cracks of the Internet tubes. PCI-SIG, who are responsible for developing the PCI Express spec, have listed some preliminary details about PCIe 4.0.
PCI-SIG says that they've decided on a transfer rate of 16GT/sec for the next-generation PCIe technology, with a study showing that 16GT/sec can be achieved over copper wires, at roughly the same power levels of PCIe 3.0, using chips fabbed with "mainstream silicon process technology".
PCIe 4.0 will be backward compatible with older PCIe devices, and vica versa. PCI-SIG haven't mentioned which encoding scheme the new standard will use, so assuming it uses the same 128b/130b system as PCIe 3.0, a 16GT/sec peak transfer rate would translate into per-late, per-direction bandwitch of just under 2GB/sec, a two-fold increase over the PCIe 3.0 standard, and nearly four times as fast as PCIe 2.0. We'd be looking at 31.5GB/sec per direction for a PCIe 4.0 x16 slot.
PCI-SIG have also hinted at reducing power consumption and keeping costs down. They say they plan to "investigate advancements in active and idle power optimizations" with PCIe 4.0. PCI-SIG also expect PCIe 4.0 to "address the many applications pushing for increased bandwidth at a low cost," including desktops, notebooks, and tablets.
We won't see PCIe 4.0 until 2014-2015, but how will high-end GPUs be by then? Will games have caught up? Will we require 31.5GB/sec of PCIe 4.0 bandwidth? Time will tell.