Rockchip RK3399 PCIe lanes only 2.5GTb/s?
#1
Okay, I may be wrong, (it's rare, but happens :-). From my reading, it appears that the PCIe lane speed is 2.5GTb/s, (aka PCIe 1.x speed), verses 5GTb/s in 2.x. (That said, the chip seems to support the protocol updates in PCIe 2.1.)

So, anyone else read it that way?

Here is a reference;

http://opensource.rock-chips.com/images/...170420.pdf
Page 89
Quote:Signal data channel data rate maximum up to 2.5GTb/s, with 8b/10b form, the maximum data rate up to 250MB/s

Next line adds the following, (which implies all 4 lanes working together);
Quote:Work in full-duplex mode, maximum data rate up to 10GTb/s, which is 1GB/s

All that means, (if I've read that right), is any NVME drive will be limited by this change. Probably not an issue for 4 lane NVME drives. Though 2 lane NVME drives, (like that nice low power Western Digital Blue), might suffer a little. This will not stop me from using a NVME drive, though I might make more effort to find a 4 lane device that has reasonable power usage.

Also, (my original reason for the research), it appears that the 4 x PCIe lanes can not be bi-furcated into 2 x 2 PCIe lanes. All 4 must work together, as either 1/2/4 lanes. (So it DOES support 2 lane PCIe devices, like the afore mentions WD Blue NVME drive.)
--
Arwen Evenstar
Princess of Rivendale
#2
rk3399 leaked manual, floating in the internet, v1.3 part 2, page 700, says:
Quote:It is compliant with PCI Express Specifications 1.1, 2.1.
...
PCIe supports the following features:
...
Maximum link width is 4, single bi-directional Link interface
...
Support 2.5GT/s and 5.0 GT/s serial data transmission rate per lane per direction
also, tests posted on this forum have shown speeds ~1.5GB/s.
#3
(08-24-2019, 08:11 PM)z4v4l Wrote: rk3399 leaked manual, floating in the internet, v1.3 part 2, page 700, says:
Quote:It is compliant with PCI Express Specifications 1.1, 2.1.
...
PCIe supports the following features:
...
Maximum link width is 4, single bi-directional Link interface
...
Support 2.5GT/s and 5.0 GT/s serial data transmission rate per lane per direction
also, tests posted on this forum have shown speeds ~1.5GB/s.

Thank you. I thought it was a bit strange to support only 2.5GT/s for a newer device.
--
Arwen Evenstar
Princess of Rivendale


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