From owner-freebsd-hardware Tue Feb 25 17:59:59 1997 Return-Path: Received: (from root@localhost) by freefall.freebsd.org (8.8.5/8.8.5) id RAA04427 for hardware-outgoing; Tue, 25 Feb 1997 17:59:59 -0800 (PST) Received: from mail11.digital.com (mail11.digital.com [192.208.46.10]) by freefall.freebsd.org (8.8.5/8.8.5) with ESMTP id RAA04414 for ; Tue, 25 Feb 1997 17:59:53 -0800 (PST) Received: from muggsy.lkg.dec.com by mail11.digital.com (8.7.5/UNX 1.5/1.0/WV) id UAA30486; Tue, 25 Feb 1997 20:52:25 -0500 (EST) Received: from usr605.zko.dec.com by muggsy.lkg.dec.com (5.65/DEC-Ultrix/4.3) with SMTP id AA26709; Tue, 25 Feb 1997 20:52:22 -0500 Message-Id: <3.0.32.19970225205045.006884cc@netrix.lkg.dec.com> X-Sender: popmatt@netrix.lkg.dec.com X-Mailer: Windows Eudora Pro Version 3.0 Demo (32) Date: Tue, 25 Feb 1997 20:52:37 -0500 To: "Jin Guojun[ITG]" From: Matt Thomas Subject: Re: Memory speed of P6-200 (256k) Cc: freebsd-hardware@freebsd.org Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Sender: owner-hardware@freebsd.org X-Loop: FreeBSD.org Precedence: bulk At 03:53 PM 2/25/97 -0800, Jin Guojun[ITG] wrote: >} At 12:48 PM 2/25/97 -0800, Jin Guojun[ITG] wrote: >} >The PCI is a 64-bit wide bus. The maxmimum memory speed you can get from >} >this bus is 1000000000 * 8 / 60ns = 133333333 Bytes/sec (no inteleave). >} >} That is wrong. The PCI is typically a 32-bit wide bus running @ up to 33Mhz. >} >} 4 bytes * 33Mhz = maximum of 132MB/s assuming almost perfect bursting >} and no wait states. >} >} 64 bit PCI doubles that maximum to 265MB/s. > >That is the PCI bus bandwidth, not the memory bandwidth :-) >PCI != MEOROY, but main memory uses PCI bus. The main memory access may be done through a PCI host bridge, but that does not mean that's it done through the PCI. A system/cpu may have more than one PCI bus (like Alpha's or high-end Pentium Pro's). Memory bandwidth is not directly related to PCI bandwidth. -- Matt Thomas Internet: matt@3am-software.com 3am Software Foundry WWW URL: http://www.3am-software.com/bio/matt.html Westford, MA Disclaimer: I disavow all knowledge of this message