PCIe 3.0 Set at 8 GTps

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The final transfer rate for the PCIe 3.0 standard finally has been nailed down, reports EChannelLine, establishing a blazingly fast 8 Gigatransfers per second (GTps) that's both backward compatible with current PCIe protocols and suitable for established silicon processes.


The speed is double the rate of the PCIe 2.0 architecture, which itself has only recently made its way to the market.


EE Times says the new standard emerged only after a sometimes testy debate at the PCI Special Interest Group over whether the I/O rate should have been set at 8 or 10 GTps. Some argued that the higher rate was necessary to maintain parity with faster processors and advanced networking technologies hitting the enterprise, although that argument apparently lost out to the desire for compatibility with the installed base of PCI equipment.


Still, the higher transfer lobby didn't walk away empty handed, as the group also decided to make a coding change the improves the efficiency of the system without jeopardizing backward compatibility. Current PCIe standards used the 8bit/10bit encoding system, which basically uses 10 bits of encoding to send 8 bits of data, which means they actually transmit about 20 percent less data than their rating -- 2.5 GTps in the case of PCIe 1.1 and 5 GTps for PCIe 2.0. By dumping the 8/10 encoding scheme in favor of a fixed-length packet technique, the 3.0 standard effectively doubles the transfer rate and provides a truer measure of its capabilities, although at the expense of additional processing power.


The full PCIe 3.0 specification isn't expected until late 2009, with any number of protocol extensions governing things like efficiency and power management. Even then, it could take two years before actual products hit the market, with the earliest systems likely to target video, graphics and other high bandwidth areas.