Messages in this thread | | | From | Krzysztof Halasa <> | Subject | Re: GT/s vs Gbps for PCIe bus speed | Date | Wed, 14 Oct 2009 23:33:50 +0200 |
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Don Dutile <ddutile@redhat.com> writes:
> so, maybe the right terms are > 2.5 GHz PCI-E > 5.0 GHz PCI-E
I don't thinks so. It would be fine for PCI/PCI-X, as there is a clock signal with a given frequency. PCI-E doesn't use a clock signal. Really, the meaningful value is a cycle time (or number of cycles per second).
Of course one could calculate or measure a frequency (or spectrum) for a given code sequence on PCI-E. For example, for something like 01010101010101 (raw code) the (base) frequency would be 1.25 or 2.5 GHz for 2.0. For other patterns it would be lower.
> No matter how many lanes, or how the data is sent (long or short bursts), > the frequency rate is a constant.
Actually, this is not the case.
> So, the data rate is not stated, just the cycle rate.
Cycle rate, sure. Frequency, no.
> This would follow the PCIX syntax as well, which is > void of bandwidth illusions.
Bandwidth, actually it may make some sense. But it would have to take #lanes into account, I'm not sure we want to do it. And it would create another confusion - raw vs effective bandwidth (like 125 vs 100 Mbps with Ethernet). -- Krzysztof Halasa
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