From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760974AbZJNVeb (ORCPT ); Wed, 14 Oct 2009 17:34:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760305AbZJNVe3 (ORCPT ); Wed, 14 Oct 2009 17:34:29 -0400 Received: from khc.piap.pl ([195.187.100.11]:33596 "EHLO khc.piap.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756549AbZJNVe3 (ORCPT ); Wed, 14 Oct 2009 17:34:29 -0400 From: Krzysztof Halasa To: ddutile@redhat.com Cc: Stefan Assmann , Linux Kernel Mailing List , Jesse Barnes , kaneshige.kenji@jp.fujitsu.com, matthew@wil.cx Subject: Re: GT/s vs Gbps for PCIe bus speed References: <4AD58EEE.4070405@redhat.com> <4AD62B52.9060200@redhat.com> Date: Wed, 14 Oct 2009 23:33:50 +0200 In-Reply-To: <4AD62B52.9060200@redhat.com> (Don Dutile's message of "Wed, 14 Oct 2009 15:49:38 -0400") Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Don Dutile 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