On Wed, Jul 02, 2008 at 02:03:37PM -0500, Matt Garman wrote: > On Wed, Jul 02, 2008 at 12:04:11PM -0500, David Lethe wrote: > > The PCI (and PCI-X) bus is shared bandwidth, and operates at > > lowest common denominator. Put a 33Mhz card in the PCI bus, and > > not only does everything operate at 33Mhz, but all of the cards > > compete. Grossly simplified, if you have a 133Mhz card and a > > 33Mhz card in the same PCI bus, then that card will operate at > > 16Mhz. Your motherboard's embedded Ethernet chip and disk > > controllers are "on" the PCI bus, so even if you have a single PCI > > controller card, and a multiple-bus motherboard, then it does make > > a difference what slot you put the controller in. > > Is that true for all PCI-X implementations? What's the point, then, > of having PCI-X (64 bit/66 MHz or greater) if you have even one PCI > card (32 bit/33 MHz)? My understanding is that this is not true for all PCI-X busses, only for some. > A lot of "server" motherboards offer PCI-X and some simple graphics > chip. If you read the motherboard specs, that simple graphics is > usually attached to the PCI bus [1]. So what's the point of having > PCI-X slots if everything is automatically downgraded to PCI speeds > due to the embedded graphics? I think there are some mobos that have both PCI-X and PCI busses. > I read some of the high-level info on the Intel 6702 PHX PCI-X hub > [2]. If I understand correctly, that controller is actually > attached to the PCI express bus. So to me, it seems possible that > PCI and PCI-X could be independant, and that PCI-X will compete with > PCI-E for bandwidth. Yes, that is possible. > [1] The ASUS M2N-LR has PCI-X (via the Intel 6702PHX) and an > embedded ATI ES1000 video card. The ES1000's specs say it has a PCI > bus interface. > ES1000: http://ati.amd.com/products/server/es1000/index.html > > [2] http://www.intel.com/design/chipsets/datashts/303633.htm best regards keld -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
