In a message dated 11/2/02 10:30:58 AM, [EMAIL PROTECTED] writes: << I have an 8500 case that I will be building a computer in. I have two logic
boards. One is from a 7600/132, the other is a 8500/120. In the specs it says that the bus speed is 45 MHz on the 7600/132 and 40 MHz on the 8500/120. However, it says the bus is controlled by the CPU card. I will be putting in a Sonnet PCI G3 450 CPU card in this computer. Both logic boards have the number 820-0752-A listed under Apple Computer on the side but the 8500/120 has two extra chips on the board between the PCI slots and the VRAM slots. Which one of these boards will be faster? Is there a way to tell the specs of a logic board just by looking at it, if you don't know what kind of Mac it came from? >> The processor card controls the CPU speed by use of an integral or fractional multiplier (the PLL chip) from an on-card oscillator which is set to the bus speed. If you change the processor card, you may in the process actually be changing the bus speed. IIRC, 50 MHz is the max for the 7500/7600/8500/9500 series of machines. 120 / 40 (the 8500 case you mentioned) is 3.0, so in this case the clock multiplier is 3. 132 / 45 (the 7600 case) is 2.93... , so in this case the clock multiplier is also 3, and the true bus speed is really 44.0. Were you to install a 200 MHz processor card, I'd bet that a clock multiplier of 4 would be used, and your bus speed would be the full 50 MHz. Were you to install a 233 MHz processor card, I'd bet that a clock multiplier of 5 would be used, and your bus speed would be 46.6 MHz. 4.5 wouldn't be used as a multiplier as that would cause the bus speed to be 51.8 MHz, which is over specification. Clock multipliers up to 7 (Beige G3), 8 (B&W G3), and even 10 (third party processor cards) are possible. But, only integral (3, 4, ... , 9, 10, e.g.) and certain fractional (3.5, 4.5, ... , 8.5, 9.5, e.g.) multipliers are possible. Use the 8500 mobo as it has full A-V, and the fastest 604e processor card you have available. -- 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:pci-powermacs@;mail.maclaunch.com> To unsubscribe, email: <mailto:pci-powermacs-off@;mail.maclaunch.com> For digest mode, email: <mailto:pci-powermacs-digest@;mail.maclaunch.com> Subscription questions: <mailto:listmom@;lowendmac.com> Archive:<http://www.mail-archive.com/pci-powermacs%40mail.maclaunch.com/> --------------------------------------------------------------- >The Think Different Store http://www.ThinkDifferentStore.com ---------------------------------------------------------------
