[The Duke of Alinor]

How is this set?
Where can we install a dip switch to change it, or is it a crystal change?
I am at 1Ghz with the overclock listed at XLR8, but need to play with the front side bus to fine tune things.

If you don't know how, perhaps you know where to find out, or where more people discuss this type of modification.

[TNproud2b]

There may not be any other FSB options. Find the clock-generator chip (PLL IC) and make note of the ID number and vendor. I have a source of info on most common models - although I'm not familiar with which ones are used on Apple motherboards.

Identifying the clock generator is only half the battle - after that, you have to manipulate the settings either thru software (like a MAC version of H-Oda's no-longer-supported 'SoftFSB' www.h-oda.com ) or you have to physically 'adjust' the clock generator (DIP switch or resoldering resistors).

To sum it up, if you've never seen anyone overclock your particular model by raising the FSB speed - then it likely cannot be done. Overclockers are a hardcore bunch of folks...and if it was possible, then it was already done and the results made public immediately thereafter.

[SkiBikeSki]

Sorry I can't help you, The Duke of Alinor, but I would like to ask you somehting. How hard was it overclock your 867 to 1GHz. And how did you check the temperature of your processor or did you just hope it runs cool enough. I thank you for any information you can give me.

I too have an 867 and want to overclock it. Please help.

[The Duke of Alinor]

From the XLR8yourmac forums:

My 867 G4 is overclocked thanks to the Mystic Room site (I can't see anywhere on the site the author's name to give him proper credit...) which shows which resistors control the PLL. http://www.bekkoame.ne.jp/~t-imai/maine.html
I used a small solderless breadboard on which I put DIP switches and 1 kOhms resistors. Then soldered wires to the appropriate positions on the CPU module on one end, and plugged them in the board on the other end. This way I can choose between 867, 933 or 1000 MHz just by modifying 3 DIP switches. It sure beats removing the CPU fan (2 screws), bulky heat sink (4 clips), CPU module (4 screws), then soldering resistors, finally put everything back, every time you want to experiment.

I'll try to take a few pictures of the mod next week. It's not pretty, but it works


Surprise when booting at 1 GHz, I got this message just before extensions load in OS 9.2.1:
"The built-in memory test has detected a problem with cache memory. Please contact a service technician for assistance."

Click OK, the Mac boots normally. Quick trip to Apple System Profiler, greeat, 1000 MHz. Ack, where's the L3 cache? Deactivated it seems... Compare these two screenshots: http://www.ifrance.com/mythical/933-L3.jpg http://www.ifrance.com/mythical/1000-noL3.jpg

Same thing with OSX, except there's no message on boot.

From time to time it will boot without complaining and the L3 is present. Also from time to time OS 9 will freeze or OSX will panic... Obviously the Mac isn't perfectly stable at 1 GHz, although I've been able to use it for hours without incidents.


I checked the cache chips. They're Samsung K7D803671B-HC25, which according to the manufacturer are rated at 250 MHz, exactly the speed of the cache when the CPU is at 1 GHz. It *should* be ok, right? Maybe it's just the 7450 which is flaky at this frequency...

So I configured the switches for 933 MHz. So far it seems stable, but I've yet to use the machine much at this frequency. Anyways I'd rather "lose" 67 MHz and get back the 2MB L3 than reach the mythical gigahertz


I did not use the dip switch setup, but soldered a wire across the pads mentioned in the Mystic article. Go for 933, it is more soldering but will work, 1Ghz is for hardcore problem lovers. As for cooling, replace both fans the one on the cpu and the big exhaust fan. Just go up 25% on the amps and plug them in. It will be louder, but that is the price of the speed boost.

Temp monitoring sucks on these units, I drilled my heatsink and ran a bunch of tests so I had a pretty good idea for calibration. I really cannot monitor my CPU temp, but my relative readings are pretty good, and I know when it will start acting up.

This is not for the amature, as the soldering is pretty small. If you have good soldering skills, go for it. I take a fine stranded wire and pare it back to two strands, tin them, and use the rest of the wire for a handle. This makes it east to position the jumper. Solder the jumper and clip it off close to the second solder point.

[SkiBikeSki]

Thank you far all that info, The Duke of Alinor. I'll need to give it some more thought. I won't go for 1GHz if it means losing the L3 chache. And maybe 933MHz isn't worth losing my warranty. I'll need to think it over. Thanks again.

Also, does anyone think there could be any harm in unplugging the PCI slot fan in my QuickSilver. I'd leave the CPU at 867, and I have no PCI cards, and the GeForce3 has it's own fan, and is currently cool to the touch. And if it is a bad idea and I do it anyway, what oddities could I expect. Could I leave the machine running 24/7 in an air conditioned room.

Any help would be appreciated. I need to make this computer quieter!

[ 09-10-2001: Message edited by: SkiBikeSki ]

[The Duke of Alinor]

Do NOT unplug the fan.
You can install a pot (rheostat) in the 0-500 ohm range. Use this to tune the speed, and quiet things down. BUT do not go below about 7 volts, the fan may not start the next time you boot. Might as well put the other fan on it too, take it in small steps, and watch the room temperature.

Or better yet, do some work and put together a temperature controlled system. Pretty simple, but I have not had the time - YET.
Searching Google should turn up a few installs you can emulate, so I will not go into it here.

BTW 933Mhz is a noticable change, but not worth it if noise is your main concern. When I do Photoshop I listen to the radio, when I play games I crank it up pretty hard, fan noise? What fan noise? Oh yes, I do notice it on startup, and shutdown, but I am usually off doing something else like coffee or lunch while it does that.

[iSilver]

Hey DOA

does this make your cable modem go any faster!!! or make you any better at Diabolo!!

iSilver

see you round!!

[ 09-10-2001: Message edited by: iSilver ]

[TNproud2b]

1GHz seems to be on the ragged edge for your G4. That doesn't mean other G4s won't do it without breaking a sweat. Don't want others to lose hope

Can you raise the core voltage on the processor? How about on the L3 cache? Can you fit a larger CPU heatsink or add a fan to the existing heatsink?

You're really close to a stable 1GHz - and probably stable right now when the L3 is disabled. A drop of a few degrees in teperature might be enough to stabilize the L3 - but a voltage bump would be more effective.

The L3 RAM chips are rated to 250MHz at the pin grid - things get ugly after you solder the chips to a circuit board.... So, 250MHz is a bit 'iffy' in the realworld. Speaking of L3, you aren't suffering very much of a performance penalty with it disabled. It's only running at 250MHz, which is ungodly slow for cache RAM. Very few apps are benefitting from it. You'd be better off with the extra 100MHz of core speed instead of 2MB of 250MHz cache - in most cases.


See if it's possible to increase the latency of the L3 cache. That would allow it to operate at 250MHz - although it would be slightly less efficient.

Yeah I'd give up the L3 in order to run at 1GHz - but only after I tried tweaking some other stuff first.

[The Duke of Alinor]

Sounds like all the old Athlon tricks.
I am not sure what I can do.
I will try to figure out the chip setup and post again.