Date: Sun, 14 Dec 1997 17:06:17 -0600 From: Allan Alford <aa@jump.net> To: Tom <tom@sdf.com> Cc: Marc Rassbach <marc@tandem.milestonerdl.com>, freebsd-hardware@freebsd.org Subject: Re: Speed of the cards? was Re: SCSI card to choose Message-ID: <34946669.73A4@jump.net> References: <Pine.BSF.3.95q.971214135812.2658A-100000@misery.sdf.com>
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Tom wrote: > > On Sun, 14 Dec 1997, Marc Rassbach wrote: > > > As I am looking at overclocking my bus speed, which cards (SCSI and network) > > out there are known to work at faster bus rates? (75 and 83 mhz bus) > > It seems that you are talking about CPU memory bus speeds, that is the > base rate of the CPU. > > PCI gives you 132MB/s bandwidth. Anything different is not PCI. > > Tom The way I understand it is this: PCI bus speed = 1/2 motherboard bus speed. Motherboard bus speed is the same as 'CPU speed' without the clock multiplier. The newest motherboards that are breaking the 66MHz speed barrier have increased the PCI bus from 33 to either 37.5 (half of 75) or 41.5 (half of 83). The official PCI standard was designed to accomodate up to 66MHz, but only specifically calls for 33MHz in its current iteration. Thus, with the newest motherboards, many PCI cards of older and/or less reliable manufacture do not work properly. To my knowledge, Cyrix is the only CPU manufacturer currently active who can support the 83MHz standard anyway. Because of their new chip, a handful of motherboard manufacturers are now claiming support for that speed. What the individual PCI card manufacturers are officially stating, I do not know. This is very new and very cutting edge technology. Research well. - Allan
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