Mac Mini overclocking

wow he took a really nice picture of the motherboard

Yeah I have seen that. ASP only reported 750MHz when it was set to 1.58GHz because 9.5x isnt a supported PLL. Any half increment multipliers that are over 5.5x do not show up correctly, and either read 0MHz, or right around half the actual speed.

EDIT: after talking with the guy a bit, it seems it may be a rom based thing. as 7.5x and 8.5x are the multipliers used to get 1.25 and 1.42GHz with as 1267MHz bus. But 9.5x and up doesnt report right.

that apple doesnt even make 2 different CPU's, they just make one that will take the added speed...

You would be wrong then. It's a trivial matter to solder on the speed grade of CPU that they want. Apple has never done as you suggested except in very rare cases where the lower speed grade just plain wasn't available and they had to have some parts right this very moment.

Apple doesnt make CPU's period. The G4 in the Mini is made by freescale (7447A). And the chips are rated for either 1.25 or 1.42GHz. Its etched right onto the top of the die. As bob said, the only time apple has not used the correctly rated CPU was in a few cases like the 867 QS which had a 933 rated CPU in it (RX933 etched into the top of the cpu die). They have never used an under rated cpu. Even the ever popular rumor that the dual 1.42GHz G4 towers were over clocked is quite false.

No, I've never seen a deliberately underclocked machine come out of Apple. There have been machines stupidly hampered by idiotic bus design (*cough*LC series*cough*) but not underclocked.

Some good info on how to open the case and
upgrade the memory.

http://www.macworld.com/weblogs/editors/2005/01/macminiinside/index.php

Read my above post, these were quite common towards the end of the 867 QS's life.

Actually on that product specifically, the CPU was available in 2 speed grades for every die, a bit slower and A LOT lower power, or faster and hot as hell. Sometimes they actually stamped both speed on the die, other times they just stamped the high speed.

Now this is VERY important. Just because som 866 is stamped 933 doesn't mean it can actually run at 933. When they decide which category it falls into, it's still being made, and a different chemical is used during one of hte doping phases, so you can't actually expect it to run at the high speed grade realiably.

While all the previous comments regarding official CPU duty ratings are certainly valid . . .

While Apple may use CPUs rated only at their nominal clock, those ratings are usually pretty conservative. I've only once failed overclocking an Apple CPU, a Sawtooth 400 which refused to run at anything higher than its rated speed. My "exceptional" Sawtooth was made at a time when Mot was having some difficulty delivering fast CPUs and is clearly rated right at its actual speed limit.

Realworld overclocking headroom varies depending on the actual CPU part on hand. I've gotten quite used to seeing 15-25% upclockability and occasionally even more. I'm quite disappointed when I can only get a 10% or less speed boost.

dan k

After Motorola got stuck at 500 MHz for over a year, they GREATLY reduced the tolerances of the processors in order to acheive higher speed grades. I've seen many G4's that can only be overclocked 3%.

The idea of underclocked CPU's comes, mainly, from the PC world. It's not uncommon for a PC manufacturer to substitute a higher spec CPU into a machine which reports a lower spec. The way it's been explained to me is that if chips become scarce, it's cheaper for the PC manufacturer to buy higher spec chips, which are in higher supply, than the lower supply lower spec chips.

Why don't the PC makers just increase the clock speed and sell the machine for more money? The answer is that most PC makers can't be stuffed to do the testing required to see if a computer will operate at a higher spec than it's rated for. Depending on what needs to be done, it can end up being more costly to retool the machine to run at the higher clockspeed than just "giving away" the extra capability unnoticed.

But, we don't mind when PC makers do that, now do we? ;-)

Cheers,

The Czar

Are you refering to the 7445 and the 7455? (7445 having no L3, 7455 having an L3) I know the first 867 had an L3, the later 867 did not. The latter is the one I am refering too. When the 867 was the low end. I know lots of people who OC'ed their 867's with chips that had 933 etched into them to 933 and they ran perfectly. Now this may just be luck of the draw of course. I know what you are refering too when they set the speed of a certain chip (although I am by no means an expert in any way in this process, I just know some of the general info).

Both of those CPU's have that feature.

Now, just because you were able to run OK at 933 doesn't mean it is a 933 part, it just means there is some headroom on yours. Your mileage may vary with overclocking.

An easy way to tell them apart is the low power version has a greenish yellow tint to it, and the high speed version is usually blue or purple.

Yes, and my Mac mini 1.33 is now running at 1.67 ... Great

Tony

Cognitive AB, Stelvio Bokföring Lön Ekonomi för Macintosh
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