Mac Mini Overclock

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Hello!! Not much of a post really, I just was so excited I wanted to tell someone. 2 days ago, I disassembled my VERY reliable Mac Mini, removed all of its internal organs, and braved the feat of working with the sub-micro-mini surface mount components found inside. Now, I just wanted to say that after two days of abusive testing... I have had success in overclocking my Mini from 1.42ghz, up to 1.58ghz. I know its only 160MHz overclock, but it has actually made the whole machine noticebly quicker!!! I've even got it reported correctly in the "about this mac" section, and in XBench as 1.58GHz!!!

I would like to try 1.67GHz, but common sense tells me that i shouldnt try, lest i have to step back down. (and redo my work)

...Bill

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Joined: Jan 20 2005
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kickin it into overdrive! way

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

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OS7.5 to 10.3.9. I LOVE CLASSIC MACS!

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hod did you overclock it with

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

John

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Joined: Sep 23 2005
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multipliers..

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.

Smile

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Joined: Sep 21 2004
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I'll be sure to give that a try...

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.

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Joined: Sep 23 2005
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Well... bringing up a dead horse...

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

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Joined: Apr 18 2006
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Cool it

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

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lol

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.. Smile

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Mac mini g4 1.67, overclocked or rare upgrade?

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!

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Are you sure it's not an inte

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

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re 1.67 mac

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.

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Re: Mac mini g4 1.67, overclocked or rare upgrade?

billykein wrote:

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.

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.

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weren't the very last of the

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

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Close

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 Wink

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Yes, the upgrade was to 1.5GH

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.

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Landed 1.83 tonight on a 1.5 mini g4

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!

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Re: Mac Mini Overclock

evilrobot wrote:

Hello!! Not much of a post really

Mine Mac mini 1.33 works at 1.67 !

Tony

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Paste instead of Pads

Hello -

I've been reading these posts with interest. I don't want to overclock myself but I do want to replace the thermal pads with arctic silver. I have a g4 mini 1.42ghz.

1) Is it correct that there is a thermal pad between the heatsink processor, AND between the bottom of the mini case and the processor? (i.e. below and above?)

2) Is it possible to replace the thermal pad on the bottom of the case with arctic silver paste? The service manual, for some reason, says not to use paste, but to replace the pad with another pad if need be. I don't know why it says this, but I assume it is possible?

3) Can the same be done for the heatsink and the processor?

4) How does one remove the pushpin/clip things that hold the heatsink in place (I read somewhere else that there are no screws fastening the heatsink to the processor)

Basically I want to replace the thermal pad on the bottom and replace any existing thermal paste/pad between processor and heatsink with arctic silver ceramique. I hate fan noise and I think that this will keep the fan from spinning up under load.

Any insights would be appreciated!

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Joined: Sep 23 2005
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well; as I am STILL daily run

well; as I am STILL daily running my OC'ed 1.42 (24hrs a day Smile )

I had moved it into an enclosed cabinet last month and I noticed that the fan was running all of the time; so I took it back apart and RE-applied the AS5

so in response....

1)YES thermal pad on the bottom of the board between the GPU and the base of the case (what it uses as a heatsink) AND a thermal pad under the heatsink.

2) I would say use a new thermal pad for the GPU. as I could not obtian one; i applied a layer of AS5 between the GPU and the thermal pad (the gap is too large to be filled w/ AS5 alone)

3) not sure what you mean? you just thouroughly clean the heatsink and processor (i use acetone) and apply AS5 evenly to the CPU.

4) VERY CAREFULLY and slowly. they are nylon; i push in on them from the top side and then try toi gently squeeze in the tabs - one at a time - until it pops through the board; then I spread them back out again using a papercliup or something and reattach.

my question to you though is why? if you are not overclocking - and your system runs fine now; you will see NO benefit whatsoever by replacing the thermal pad with AS5; and in fact might cause issues by weakening the contact that the GPU has with its thermal pad.

I would personally advise AGAINST doing this if you are not overclocking; as it will not reduce fan usage or anything really; and just poses way more potential pitfalls than it does any tangible benefit...

EDIT: also wanted to add that doing this did not make my fan run any less; I just ended up moving to mini OUTSIDE of the cabinet - as any solution I attempted still resulted in it running too hot. Smile

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Thanks very much for your res

Thanks very much for your response. It is very informative.

I didn't realize that the thermal pad on the bottom was for the GPU. It is good to know that there is not enough space for thermal paste alone, and that the thermal pad fills that gap.

Another question, now that I have more info: It looks like the service manual says to get at the processor if I wanted to get rid that thermal pad, I would HAVE to remove the internal frame. In doing so, I would automatically mess up the seal between the GPU and the thermal pad... right?

Meaning there is now way of getting to the processor without removing the internal frame...? Isn't the same true though, if I wanted to replace the HDD? I would have to remove the internal frame thereby severing the GPU-thermal pad connection?

The reason I want to do it is to bring down temps so that the fan would not spin up under load. I suppose, by what you are telling me, there would be no benefit in doing so...

Thanks again!!

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to change the HD; etc - you d

to change the HD; etc - you do have to remove the internal frame; this does not break the connection with the thermal pad + the GPU; as to take out the internal frame the logic board still stays in the machine.

To take off the Processor Heat sink you need to remove the motherboard to get out the "push pin" clips; which will separate the GPU contact with the bottom of the case.

Truth be told; if you are very careful; and the GPU hasn't really heated up that much; you may be able to make a "clean break" between the GPU and the thermal pad; without damaging the thermal pad.

but if it has got up to some reasonable temperatures; most likely parts of the thermal pad have bonded to the GPU and it will need to be replaced.

pretty much - short of liquid cooling; or removing the top case and affixing a VERY large passive heatsink; I am reasonably confident that the fan will spin up under heavy load.

I'd suggest not keeping it in a cabinet; not keeping anything within about 6-8 inches of the mini, and not stacking anything on it.

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Joined: Feb 9 2009
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Ok, good to know! I'm not go

Ok, good to know! I'm not going to want to order a new thermal pad if I muck this up, so I'm not going to touch it! If one day I want to switch out the HD, I'm glad that I won't break that thermal pad connection. I'll just live with the noise when it spins up. This g4 is getting old, and sometimes I push it to its limits. But I don't plan on upgrading anytime soon.

Well, thanks again!

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Hello again evilrobot! Wha

Hello again evilrobot!

What about a solution like the following?

http://blogs.vertigosoftware.com/jatwood/archive/2006/05/17/Tracking_down_the_Mac_Mini_fan.aspx

I actually have one of those resistors laying around from when I used to use a PC. If this works, I would be willing to sever the connection between the heatpad and GPU, and perhaps apply a thin layer of thermal paste to it so that the connection is not too bad.

Any idea on which wire is positive? Think that that blogger has it right that it is the first wire? Even though he says he is going to mod an intel mac mini, I am pretty sure that the fan there is from a G4 mac mini. What do you think about this, in your infinite knowledge? I really like *quiet* computers. I'm not worried about overheating, so long as the fan continues to turn.

Thanks!!

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Joined: Sep 23 2005
Posts: 316
although I would be a bit lee

although I would be a bit leery of that solution on a machine as tiny as our Mini's; I assume that it WOULD achieve your desired goal.

you would NOT need to remove the logic board to do that to a Mini (read; dont worry about the thermal pad on the GPU; you wouldn't be messing with it)

If my vertigo that I am currently experiencing passes tonight I will take apart my mini again and post some pics on my Flickr account for you so you know what to work off of.

EDIT: The man who's site that you posted to; Jeff Atwood - that name sounds VERY familiar; like I think I may have worked with him in the past... I wish that I could place it...

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Joined: Feb 9 2009
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Oh - I don't want to put you

Oh - I don't want to put you through any trouble. Please don't worry about it. I have the mac mini service manual that has pictures of doing this kind of thing every step of the way. So again, don't worry about it please.

Instead, I might use my G5 power mac which I have modded with quiet fans and fan controllers, and it is inaudible, and move this mini back down to the living room where I can use it to watch Hulu on my flat panel tv. The only reason I ever switched them was because the G5 was better at handling flash, but, so be it.

Again, thanks for your offer, but I'll manage on my own with the service manual. If I do do this, It will be within the next month or so, and I"ll post back my results.

Thanks again!