Where is the Clock Crystal?
I used an application
CPUFSB on windows to overclock my athlon PC. It works by changing BIOS settings while in Windows. I tried to do it on my Mac Mini but without results. I wonder if it is possible at all since the mini only emulates a BIOS and it might even emulate a BIOS that has no "System Management Bus connection".
Changing the FSB works by changing the frequency of the clock crystal. You need to know which crystal is in your system. A clock crystal looks like this:
I looked at pictures from disassembled mini's (
1) (
2) (look at download for high res), but could not find one.
So I opened up my mini and indeed found a crystal. I don't have a digital camera, but I attached a schematic of what is underneath the airport card. The chips read:
Crystal: 24. 576H6B
agere L-FW323-06 1394A LINK/PHY 0607S 50284247
B: SST 25vfo 16B 50-4C-S2AF
32 768 KDS0604
+330 e62
+J8 EP
F: KL1 T2
G KL1 T2
the Agere chip seems to be firewire (1394). And also the crystal is attached to the agere chip, so I don't think It's the frequency chip. Under the ram slots there is pretty much nothing. I have not lifted my mainboard completely out, but by looking at the pictures I concluded that there was no clock crystal on the mac mini.
I am now confused how the BUS-speed is controlled on the new intel chips. It might be that they are using onchip crystals. On the internet i found two documents about the PLL bus controller of the 945 chipset (
1# PDF 2.1 MB) (
2# PDF 2.3 MB).
Traditionally you could also solder jumpers on a mainboard to change the CPU-frequency. I don't know if it's possible on the new chipsets. The recent overclocks of
core duo's and
core celeron's (on PC's) were done by increasing the FSB in bios.
arstechnica have looked at the chipset of the
iMac and found:
arstechnica.com said:
Rumor has it that the iMac Core Duo uses a custom chipset designed by Intel. From looking at pictures of the chips, we were able to do some deduction from the chip numbers. The northbridge chip looks to be an 82945GM, which identifies it as the Mobile Intel 945GM Express chipset. According to the S-Spec number (SL8Z2), it's a standard Intel chipset and therefore not an Apple-specific variant. The southbridge appears to be an ICH7-M, which has support for a Trusted Computing module.
Finally: has anyone looked in changing FSB settings from within EFI (extensible firmware interface)?
. I know the chip can half its multiplier if there is little load on the CPU, I'm guessing thats software controlled or driver controlled somewhere.
