>Date: Tue, 17 Dec 2002 16:29:27 -0800 >From: E McCann <[EMAIL PROTECTED]>
>At 01:14 PM 12/17/2002, victoria.duggan typed thusly: > >>Forgive me for sounding dump, but is the bus speed of a 7300 controlled from >>mother board or cpu, and if i have installed a 233mhz 9600 card will i >>have increased my bus speed? or will it still be the same. > >Mainboard. No, CPU card. All of the PowerSurge family (x500, x600, 7300, PowerTower Pro, PowerWave, S900/J700) have their bus speed set by the CPU card installed. The CPU card has an oscillator on board which goes directly to a clock buffer on the CPU card. The clock buffer splits the oscillator signal into several in-phase clock signals. One of these clock signals goes to the CPU chip on the CPU card. The other six go to pins 9 through 14 of the CPU card connector and from there to the motherboard. There are certainly limits on how high a bus speed the motherboard can run at, depending on the motherboard. But the actual clock signals that set the bus speed come from the CPU card. My experiments with adjustable CPU cards seem to indicate that the top bus speed may be more often limited by what the CPU card can tolerate rather than the motherboard, but I have not tested a statistically significant sampling. I have simply observed that a given CPU card which will run at 60 MHz bus speed in one machine seems to do fine at 60 MHz in every other machine in which I install it. A CPU card which will not go above 49 MHz in one machine, also seems to be limited to 49 MHz in the other machines as well. So your limiting factor for bus speed can be the tolerance of your CPU card as well as your motherboard. From the reports I've read, it does appear that motherboards with built-in video seem more limited in the bus speeds that they can tolerate. One final note. Some folks set store by the fact that a given (e.g.) 8500 shipped with a 150 MHz CPU vs. a 132 MHz CPU meaning that it shipped with a 50 MHz bus speed vs. a 44 MHz bus speed. That doesn't matter at all. Apple put the exact same motherboard under the 132 MHz CPU card as they did under the 150 MHz CPU card. It's a simple accident of assembly, which CPU card the motherboard was paired with before shipping. Actually, it could matter in a small number of cases. There are a few reports of 7500 and 8500 machines not tolerating bus speeds higher than 45 MHz, and knowing that a working machine shipped with a 50 MHz bus CPU card would tell you that you're not getting one of the rare wimpy ones. 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
