# What is the maximum run length in PCIe gen 3 serial stream? [closed]

PCIe gen 2 uses 8b/10b and the run length is 5. What is it for Gen 3? Thank you for help.

## closed as too broad by Bence Kaulics, Daniel Grillo, Sparky256, Voltage Spike, Dave Tweed♦Jul 23 '16 at 16:05

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• 128/130b encoding. Don't know what the run length is. – Tom Carpenter Jul 18 '16 at 23:36
• Yes! Thx. But what is the worst case run length? I suspect some sort of scrambling is also done on the data. – shparekh Jul 18 '16 at 23:43
• Scrambling is done, yes, using the polynomial $G(X) = X^{23} + X^{21} + X^{16} + X^8 + X^5 + X^2 + 1$. If you can find a copy of the PCIe Base Spec Rev 3.0, the scrambler is described on page 213 onwards. – Tom Carpenter Jul 18 '16 at 23:47
• This might also be useful reading. – Tom Carpenter Jul 18 '16 at 23:48