Mac Mini Overclock

kickin it into overdrive! way to go....

hod did you overclock it without killing it? sounds like suicide if you dont have a guide or something like that.

John

the mini is really no different than any other G4, and it uses essentially "jumpers" to open and close different traces that set the clock multiplier and such, except that instead of the actual jumpers that you would encounter on say a beige G3, or something like that... the "jumpers" are actually submicromini surface mount resistors (general opinion is that they are just 0 ohm resistors, essentially opening and closing the "switches", but my test with my meter shows that they are 1K ohm resistors.. i also found a data sheet somewhere that says 400-100 ohms is appropriate for reliability.) so, other than the fact that these resistors are just about the size of a human hair, it is only a matter of changing jumper positions. There are several charts online that show which jumpers result in which speeds. in the case of the mini there are 5 jumpers.... only 4 are visible on the bottom of the board R362, R358, R355, and R351. the 5th "jumper" is R52, and that is found next to the processor itself... to get to it you have to remove the heatsink, and thermal gasket... after that you can change R52... but you only need to move that jmper if you want to go above 1.58GHz, and at that point, youd also have to replace the thermal pad on the heatsink with some artic silver or something. after changing to 1.58GHz you also have to patch the frequency tables in open firmware (hint.. nvedit) so it displays correctly... if you DONT, and you do successfully overclock to 1.58GHz, it will show up in "About this Mac" and so forth as a 750MHz G4... not a big deal, because it really is 1.58GHz... the system profiler actually doesnt test to see what the speed is, it just looks up in a table and spits back the text contained in the cell for the selected frequency multiplier... you could just as easily make it say "G4 Pizza Edition" or something. in the case of my mac mini, it was already a 1.42GHz mini from the factory, so to jump up to 1.58GHz, all i had to do was remove R351. Now, for any of you who would like to try overclocking your mini... some things to be aware of... the 1.25GHz minis and the 1.42GHz minis shipped with a different heatsink... while this doesnt matter going up to 1.42GHz (even 1.5 in most cases) the 1.42GHz's heatsink is required to go above 1.5 and be reliable (not POSITIVE... but i think the new ones are all shipping with the same, larger heatsink) Also, you may have better luck OC'ing the 1.42 because the processor might be of a tighter tolerance, so it would be able to handle faster speeds. Heres is the "table" for which speeds you get just changing the 4 (more) easily accesible resistors:

Speed R362 R358 R355 R351
1.25GHz yes yes yes -
1.42GHz - yes - yes
1.50GHz - - - -
1.58GHz - yes - -

Now, again this might set you off... but here is a photo of where they are, and what they look like... now, just to help yo uimagine scale... that black button, is actually the base of the heatsink pad and is actually a smaller diamater than say a motherboard mounting screw. (and the resistors arent red on the board... this is just to show in the pic):

and yes, unless you are VERY confident in your abilities, and unless you check what your doing several times... it COULD very well be suicide. this mod is NOT for the faint of heart. However, if you have strong soldering skills and are not afraid of the possibility of bricking your mini (and of course, invalidating your warranty) it also IS NOT difficult at all. from dissassembly, mod, reassembly, Open Firmware edit, and reboot... it took me an hour.

when my mini comes off warranty. As much as I love to tinker, it's the first brand new mac I've ever had, and while I'm completely confident in my soldering skills, if it ever dies for any reason I'd need to be able to bring it back in for service.

OK, Follow up and an update.

My machine has run PERFECTLY, 24hrs. a day, for more than the last year at 1.58GHz.

.::WOOT!::.

So, last night I decided to press my luck, I removed the processor heatsink, removed the R52 resistor and replaced the heatsink (using same factory thermal pad...) Fliped her back over and changed the order of the PLL resistors.

First I went for 1.83GHz ... I turned the machine on, got the startup chime, heard the drives spin - but got no video or power to keyboard / mouse

Then I stepped down to 1.67GHz, things SEEM to be working. Machine has a crash when running XBench, I'm not entirely sure what thats about. Anyway, right now I'm posting this from my 1.67GHz G4 Mac Mini, which was orig. a 1.42GHz mac mini - an extra 250MHz for about a hlaf hours work sure does seem worth it. Im not convinced of the stability yet, however. I finished upclocking it about five hours ago, and Have only done a little web browsing, iTunes and some World Of Warcraft. Like I said, XBench crashes... I'll investigate when I get home from work, maybe its as simple as replacing the thermal pad with some arctic silver.

Just thought I'd share.

(and, in MUCH less exciting news, I also overclocked my Rev. D 333MHz iMac to 400MHz yesterday - seems to be rock solid.)

/Bill

DEFINITELY replace the thermal pad. Usually when I overclock, I replace or add fans as well. Also, I bet there is a fairly simple way to boost the voltage going to processor. That is another way to get G4s to run faster.

If you have trouble finding out how to boost your core voltage on a Mini, see if you can find out how its done on a MDD. Id be willing to bet it has the same jumpers labeled the same way.

Anyway, is there a fan in the mini? Or maybe a good place to add one?

-Chris Placzek

No, no fan, no room for one - and I ahve not as of yet found anyway to boost the core voltage. However, I DID get rid of the thermal pad and replaced it with some arctic Silver, and its been running at 1.67 since I made my last post to this thread. It was only rebooted to move things around on my desk..

Hi guys,
some time ago I bought a second hand (but perfect, still the plastic on, not one scratch) mac mini g4 for very few euros.

when I open system profiles it says that this mac mini g4 runs at 1.67 ghz, and so teoretically never be produced! the mac is working well, but sometimes has some "bizzarre" behaviours.

Now, I think it is unlikely that the person that sold me has overclocked it, especially considering its perfect estetics it seems never used, but I would like to have a way to verify without opening it (i am not able in technical things..).

from the number of series, or from somewhere else, you know if is it possible to assess if this is just a rare g4 or a hack?

thanks!

Are you sure it's not an intel? The first gen Intels came in 1.66GHz and 1.83GHz.

yes.. are you sure its not an intel?

what ports are on the back?

if it has (from looking at the rear, left to right):

Power, ethernet, modem, DVI, (2x) USB ports, (1x) Firewire port, and (1x) audio port (out only)

then it is a G4 mac mini and as such never came in 1.67 (although I oc'ed mine to 1.67 and it looks factory new... you cannot tell until you disassemble the entire machine and remove the processor heatsink)

if it has (from looking at the rear, left to right):

power, ethernet, (1x) Firewire port, DVI, (4x) USB ports, and then ABOVE the USB port... (2x) Audio plugs (one line in/optical in, the other line out/ headphone out/ optical out.)

then it is an Intel Mac Mini.

It could be the former owner was just very careful opening the case and left no marks after overclocking.
As noted above, 1.67 GHz is one of the clock speeds attainable on the G4, and its occasional bizarre behaviour may be a related thermal problem.

If the system profiler is claiming a G4, that's your answer.

weren't the very last of the g4 mac minis silently updated? I remember reading of 1.53GHz ones and maybe 1.67 ones.

The silent upgrade was 1.33GHz (formerly 1.25GHz) or 1.5GHz (from the 1.4GHz).

Back to evilrobot's overclock, I'd been looking at one of the G4 Quicksilver overclock sites here, and thought the use of dip switches was a great idea.
I can see them being used in the mini to provide a changeable overclock, with the possible benefit of positioning the switches so they're accessible without having to take the case apart. You're on your own for finding that position, though, unless someone wants to donate a mini to me

Yes, the upgrade was to 1.5GHz. Also, 64MB VRAM and a +R DL capable burner (Matshita DVD-R UJ-845). I don't have the need/heart to try an overclock on my 1.5GHz mini.

Got adventurous this evening with a speed bumped Mini g4. I removed the heat sink and confirmed that the chip was in fact rated for 1.5GHZ and it was. I also found it was a 7447B which was interesting as I had anticipated the 7447A. This was a particularly easy over clock as I had to only unsolder R52. Not that removing R52 is something for the faint of heart, given its size and locale.

The other pads on the underside of the board are empty in the 1.5 ghz config. So I was able to just short the two of them for 1.83. (I figured I could always add the 3rd short if 1.83 wasn't stable...but it was!) I used this little tube of stuff called a 'circuit writer pen'. They sell 'em at radio shack for bread boarding, and it was just the thing to short out the pads. Best part is if you get sloppy you can just wipe it away with rubbing alcohol and try again. I did remove the crappy looking pad from the heat sink, and replaced it with AS5. That may have helped with my efforts, as the original transfer pad was looking pretty well worn.

Anyway, it's run reliably playing Halo for around 4 hours, and so far no problems. Seems a tiny bit louder, and definitely hotter air being exhausted from the rear vent, but otherwise, rock solid. +330 mhz isn't too bad considering no voltage boost and no additional cooling. I guess these chips are quite capable.

It's a shame they had to saddle it with a 9200. At least I was lucky enough to open what I thought was a 1.42ghz with 32mb Mini and find a 1.5ghz with 64mb. I've tried using ATIcceleratorII but I get crazy artifacts with even the slightest over clock. Anyone ever repackage their motherboard and add a real heat sink/fan to the GPU or VRAM? (VRAM is labled as HY5DU573222F-33 which I believe is rated at 300mhz ddr.) It would seem as though if you mounted it on standoffs in a taller, however similarly sized enclosure, you could accommodate such an arrangement.

So, if you have a Mini which shipped at 1.5ghz, and are reasonably good with a soldering iron, or know someone who is, you can potentially unlock a respectable little boost!

Mine Mac mini 1.33 works at 1.67 !

Tony

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