Jeff Walther wrote: >The 9500 has two separate PCI bus controllers. The PCI bus >controller (Bandit chip) cannot give different priorities to the >lower slots than the upper slots, because the upper slot controller >has no influence over the priorities on the lower slots and vice >versa. > >The 9500 has two completely separated PCI busses. The place they >meet is on the CPU bus because the two Bandit chips also live on the >CPU bus. It is possible that the Hammerhead chip which arbitrates >the CPU bus, gives one Bandit priority over the other, but I have >never heard that it does. If it did, I would expect Bandit 1 (upper >slots) to have higher priority because Bandit 1 controls Grand >Central as well as the upper three slots. Grand Central handles all >the motherboard IO as well as the PCI slot interrupts. > >It is also possible that Grand Central gives interrupts from some >slots higher priority than interrupts from other slots, but again, I >have not read that it does. >
So why would moving PCI cards that don't do too well from the upper three slots to the lower ones give better performance, as in this case the SCSI card? The video card seems to be destined to on one of the lower three. I am just guessing that the 9500's design must have come from the 8500 with three existing PCI slots and those slots/bandit chip were moved lower to give room for another 3 extra PCI/bandit chip set. The cpu then recognizes the lower ones being native than the upper ones. Charlie -- PCI-PowerMacs is sponsored by <http://lowendmac.com/> and... Small Dog Electronics http://www.smalldog.com | Refurbished Drives | -- Sonnet & PowerLogix Upgrades - start at $169 | & CDRWs on Sale! | Support Low End Mac <http://lowendmac.com/lists/support.html> PCI-PowerMacs list info: <http://lowendmac.com/lists/pci-powermacs.shtml> --> AOL users, remove "mailto:"; Send list messages to: <mailto:[EMAIL PROTECTED]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive:<http://www.mail-archive.com/pci-powermacs%40mail.maclaunch.com/> Using a Mac? Free email & more at Applelinks! http://www.applelinks.com
