[Cipher13]

I was just thinking about overclocking my Sawtooth G4 400...
Anyone got any ideas how far I should overclock my rev. 2.9 G4?
From 400 to 450 seem safe? Obviously I can't go over 500 because of errata...
I searched the forums and doesn't seem to be much about G4 overclocking, and can't find instructions on how to do it either...
TIA

Cipher13

[MacNZ]

Ain't it fast enough already Cipher??
Well you've already limited yourself to 500mhz so it's pretty much trial and error for your chip between those speeds. I have heard of a G4 clocked to 450 as you said with no worries. i would be tempted to go to 466 if the chip held up.........good luck ey.

[Cipher13]

heh, a computer can never be too fast . I would take it to 466, but the instructions I found only show how to make 350, 400, 450 or 500...
If anyone knows of any decent instruction, please post the URL.
TIA

Cipher13

I've clocked my sawtooth 350 to 450. Below is a link with the procedure I used.
http://webusers.warwick.net/~u1034376/web/

-corwin

[Cipher13]

Thanks - was it hard to do, soldering and all? I have experience with soldering surface mount chips, which are damn small - will that suffice for this job?

Cipher13

[P]

To get to 466 you would have to change the data bus to either 66 or 133, and that is likely more work than just changing the processor multiplier. Has anyone changed the data bus speed? Any got it to run in 133 (it should be possible, with the right DIMMs).

[MacNZ]

Thanks for that 'P'. I don't have a G4 so I wouldn't know............money for the poor??!

[Evangellydonut]

I think you can actually OC the G4s to beyond 500Mhz...as someone pees did on their Yikes and had no problems with it. The HD bug was somewhat obscure, but had to be addressed nonetheless...Also, OC the CPU to 500+ Mhz and have it actually run/rate at 500Mhz is different.

Xlr8yourmac have some good instructions as to how to OC it, and it sounds kinda challenging. Keep in mind that it's probably better if you increase the core voltage of your CPU, and while you are at it, OC your Mobo too, that is if you have PC133 RAM to feed that thing. I've had some experience with surface mounts too, and the only thing I can think of is to use some tape to tape down the resistor while soldering, also, I think those resistors will blow if too hot...goodluck and let me know how it turns out.

This was the toughest mod I've done yet. You might blow the resisters by overheating them. I resolved that problem by using wire wrap soldered onto the resistor pads and then using 1/4 watt resistor from the leads.

Clocking the bus to 133 is possible but only with some firm ware changes. I guess apple programmed blockes to prevent that sort of thing. M. Isobe is wrking on a utility to remove? the block.

It would be nice to clock the bus but I actually think that is riskier than clocking the cpu.
Corwin

[olePigeon]

What about overclocked a G4 500 to 550?

I took a look at the motherboard and the processor isn't even ZIF anymore. Really bumbed me out.

[Evangellydonut]

Some managed to successfully OC their sawtooth to 550.

The G4 CPU is on its own daughtercard, and is rumored that the pin-out for the daughtercard connectors of the single and the dual G4s are identical, which means with a bit of firmware hack, you can upgrade your single CPU G4 to dual (along with the proper heat sink...)

[micha schraven]

I once had a powerbook g3 300 boosted to 450mhz in my hands. It might seem extremely fast, but in fact is wasn't. the cache was too slow to keep up. The result were multiple crashes.

I always wondered about speeding up my powerbook 500mhz. As far as I know the keyfactor in succesfully overclocking is cooling. And that's what I am worried about.

Industrial processors like the Cray all have some sort of cryo-cooling. as long as you can cool the processor you have theoretically infinite speed. Am I right?

[micha schraven]

oh yeah, the limit of an ibook 300mhz is 666 mhz

so wait. Question. I have a copper G3 running at 333mhz. Im going to O/C it, but should I go to 400, or 433? If I went to 433 would my 512 k of cache not be fast enough, and I'd crash a lot? What do you think?

Ca$h

[Misha]

The cache speed is relative to the clock speed... the cache speed is defined by a ratio, not a specific figure, so if you have a 400 MHz Mac with a cache running at 200 MHz, and overclock the chip to 500 MHz, the cache will automatically adjust to 250 MHz since the ratio is 2:1.

As for crashing, with overclocking nothing is certain... trial and error.

I know that part Misha, but Micha (misha, micha, whatever hehe) said that the cache was too slow to keep up with the chip, which CAN happen. Thats what makes some athlons so easy to O/C, the L2 Cache is ON the chip, like in the die.... so it is pretty speedy.

Ca$h

[Evangellydonut]

you can always underclock your cache to less than 2:1 speed if necessary to achieve stability...

Are you sure you can underclock the backside cache all the time? I mean, what about durring startup when the rom is loaded and before any SCRI extentions? I thought that the cache was set by the rom to 2:1? If that was the case then you could never disable the cache before the proccesor ran it at 2:1 and that would cause a freeze! Justa thought.
Mr. Corwin

[Evangellydonut]

Good point...I was just thinking 'bout Xlr8's utility to OC your cache and SP...which I guess could be altered after ROM loading...but then, there's that debate 'bout how ROM is loaded into RAM (the startup sound thread), and if you can change that, all's well...

If all fails, there's always firmware tweaking. (since its the Mac Bios 'n all...)

Hi!

I've just tried to overclock my G4-400 (AGP, non-GB) to 500 MHz. At first it seemed stable, but trying to run a filter in Photoshop on a 60MB image finally made the machine crash (after about 30 seconds).

Now I've soldered everything back to the original configuration and the machine works just as before.

Before I try 450 MHz, did anyone ever get a stable configuration with this? And: Would stronger cooling help to run reliably at 500MHz?

Sebastian