gigabit ethernet w/ 32bit PCI

"Paul Gunson" <paulg DeleteThis @spammenot.com> wrote in message
news:bufno0$h1p$1@lust.ihug.co.nz...
 > weird question: what would be the max transfer rate (roughly) of a 64bit
 > PCI-X gbe card, that was installed on an older UDMA33 motherboard (with
 > pentiumIII) with 32bit PCI slots and ATA100 hard drive...? how would
 > this compare to more modern UDMA100 motherboard (still only 32bit
 > PCI)...? and then what is the actuall max transfer rate if that gbe card
 > was in a PCI-X slot...? cheers.

Well, there are two things to clarify here. First, whether the motherboard
supports UDMA33 or 100, has no bearing on the PCI spec of that motherboard;
they are just separate features. Second, the PCI-X card will operate like a
regular PCI card if plugged into a regular PCI slot; so none of its 64-bit
features is enabled.

So the transfer rates of various PCI buses:
32-bit, 33Mhz PCI: 32 * 33 / 8 = 133 MB/s
64-bit, 33Mhz PCI: 64 * 33 / 8 = 266 MB/s
64-bit, 66Mhz PCI: 64 * 66 / 8 = 533 MB/s


So a Gigabit Ethernet card by definition has a maximum transferal rate of
125 MB/s (1000 Mb/s / . So the GBE card will pretty much saturate the
whole 32-bit 33Mhz PCI bus, if it goes at its maximum speed.

Yousuf Khan<!-- ~MESSAGE_AFTER~ -->