Wednesday, July 20th 2011
Intel Mulls Propagating PCI-Express 2.0 x2 Interface
PCI-Express x1 met its match with the recent flood of devices such as 2-port SATA 6 Gbps and USB 3.0 controller chips that maintain their tiny package sizes thanks to a single-lane PCI-Express bus connection. The single-lane connection is already saturated with these kinds of devices: SATA 6 Gbps is moot with 250 MB/s per direction bandwidth of PCI-E 1.1, and could face bottlenecks with 500 MB/s of PCI-E 2.0, it is a similar case with USB 3.0 controllers. Use of PCI-Expresss x4, the bigger PCI-E bus standard, is a bad option as it increases PCI-E data pins by four times (significantly impacting chip package sizes), while eating into the limited lane budget of today's desktop chipsets.
The next best thing is PCI-Express 2.0 x2. While 2-lane PCI-Express is hypothetically possible, it has never been implemented by motherboard manufactures, neither on client, nor enterprise platforms. PCI-Express' parent organisation PCI-SIG doesn't have a slot or port specification for PCI-E x2, either. Intel seems to be of the idea that PCI-Express 2.0 x2 will provide immediate relief to manufacturers of small-footprint devices such as inexpensive third-party USB 3.0 and SATA 6 Gbps controllers, it provides a total of 2 GB/s bandwidth, 1 GB/s per direction, which greatly alleviates bandwidth bottlenecks, while not significanly increasing chip pin-counts. PCI-Express 3.0 is still in its infancy, while implementing PCI-Express 2.0 x2 is the easier, short-term solution. It will cause minimal R&D overhead on manufacturers to implement it. PCI-E 2.0 x2 will fit nicely into the limited lane budget of today's desktop chipsets.
Source:
VR-Zone
The next best thing is PCI-Express 2.0 x2. While 2-lane PCI-Express is hypothetically possible, it has never been implemented by motherboard manufactures, neither on client, nor enterprise platforms. PCI-Express' parent organisation PCI-SIG doesn't have a slot or port specification for PCI-E x2, either. Intel seems to be of the idea that PCI-Express 2.0 x2 will provide immediate relief to manufacturers of small-footprint devices such as inexpensive third-party USB 3.0 and SATA 6 Gbps controllers, it provides a total of 2 GB/s bandwidth, 1 GB/s per direction, which greatly alleviates bandwidth bottlenecks, while not significanly increasing chip pin-counts. PCI-Express 3.0 is still in its infancy, while implementing PCI-Express 2.0 x2 is the easier, short-term solution. It will cause minimal R&D overhead on manufacturers to implement it. PCI-E 2.0 x2 will fit nicely into the limited lane budget of today's desktop chipsets.
29 Comments on Intel Mulls Propagating PCI-Express 2.0 x2 Interface
We are against it because there's a high likelihood that if you buy a 2x card, either the system BIOS is going to reject it or you're only going to end up with 1x performance. In both cases, it defeats the purpose (just buy a 4x card and a non-POS motherboard and be done with it).
It's pretty obvious PCI-SIG felt that increments smaller than 4x were unnecssary; there's no reason for that to change today. We're talking like 3/4 inch longer on the slot and 4 times the performance. The difference in size is moot because virtually all motherboards are designed for at least one 16x slot.
If they were getting rid of everything larger than 4x, for example, then I could see justification for a 2x card. That simply isn't going to happen though (at least not any time soon).
Sorry, but you don't have a valid argument against. Adding a 2x specification will not harm anyone, but could help at least a fringe market. Nothing you have stated has suggested otherwise.