Re: PCI bus speed on OldWorld PCI macs
On Thu, 01 Aug 2002 13:50:07 -0500
Chris <firstname.lastname@example.org> wrote:
> Pardon my ignorance but in a conversation a while ago someone asked
> this listserve if upgrading to 100mbs ethernet on an older PCI
> powermac lab would be worth it to improve terminal performance.
> Most people seemed to say 'NO' because of the limits of the PCI bus.
100Mbps Ethernet = approx. 10-12 MB/s. PCI bandwidth is 132 MB/s (or
80-90 MB/s in practice, I've read here recently). Plenty of headroom. I
doubt such a card would even get much in the way of other PCI traffic.
In short, the answer is 'YES', a faster Ethernet interface will improve
> -what is the speed of the PCI bus on an older powermac? (is is 50%
> bus speed?)
As Ben said, it is 33 MHz. It has no relation to the system bus speed,
and remains the same even if you overclock the system bus.
> -What about the onboard video and ethernet? Is that effected
> performance wise by the increased bus speed?
Video possibly, but keep in mind that on-board Ethernet is only 10Mbps,
which is only about 1 MB/s throughput at the best of times, hardly a
significant load on the system bus.
> -Should I worry about old PCI cards not working at "overclocked" PCI
> bus settings on the PPC-MAC side?
No, because you can't change the PCI clock.