>Date: Wed, 9 Oct 2002 09:26:08 +0800 >From: Charlie Reyes <[EMAIL PROTECTED]>
>Jeff Walther wrote: > >>The 9500 has two separate PCI bus controllers. >>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 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. That's a reasonable guess, but it isn't the case. The upper three slots in the 9500 are the slots wired the same as the only three slots in the 8500. The lower three slots are the add-ons. I don't know why moving the video card improved performance. Especially if you had it in A1 to begin with. It could be that the traffic from Grand Central which controls MB IO was slowing it down somehow. In the upper slots it would have been sharing Bandit 1 with Grand Central and Grand Central gets a higher priority on PCI Bus 1 than any of slots 1 - 3. But I really don't know for sure. I know how the things are wired and little bit about the arbitration scheme, so I can shoot down some theories, but I don't know enough to answer most questions about the finer points of operation. Jeff Walther -- 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
