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Thread: Max % resistor tolerance for OEM apple processor clock registers?

  1. #1
    Join Date
    Feb 2006

    Default Max % resistor tolerance for OEM apple processor clock registers?

    Hey all.

    Im back so quickly due to a couple random crashes ive had after recently overclocking my Mac.

    The computer crashes at random in a fashion similar to if i desolder one of the clock register resistors whilst the system is running. iTunes music hangs and it kind loops the last note over again indefinately. That happens whether the computer crashed "on its own" or if i desolder one of the clock register resistors.

    I am curious to know if my crashes could be caused from using resistors that are too far out of tolerance to be used with apple computers. Im using 1000 ohm resistors for the clock registers. However, theyre 5% tolerance from radioshack and test at around 910 ohms average on the ohm meter. The original, tiny clock register resistors had more like 930-940 ohm on the meter, but they all blew away they were so small so i cant use them again. Theyre in the carpet somewhere.

    Is it possible the clock chip is confused with these resistors due to them not having enough ohms?

    Does anyone know for sure that if thoust dosent have exactly 1000 ohms for these registers that the clock chip will get confused?

    Thanks again.

  2. #2
    Join Date
    Jan 2002
    NW Montana


    Ben welcome to Guru's

    Most of us here don't get into the depth of what you are doing with tweaking the stock processors. Except the ol' ZIF days I am sure there are sites that do. Most here need a plug and play upgrade processor and bigger jump than 10-20 percent they need things to "run solid" as it is their income often.

    I am jealous reading about you playing and tweaking processors. I'd love to know more.... but just no time or nuf smarts.


  3. #3
    Join Date
    Feb 2006

    Default Hi

    messing with this kinda sucks though. It was never meant to be worked on.. ever.. EVER again hehe!

    I, too, would love a new mac, but for the moment im unemployed and stuck with an old powermac G4 866 that my parents got for me some years ago.

    Macs are wonderful computers. They seem to be built quite well (for the most part). Every mac ive had, including my first performa were built so well and lasted indefinately. (I still keep my old performa 405 in working condition). Theres usually good compenents in them (except for the old 5 flavors imacs that had seemingly sabotaged video boards). The thing with me is that Ive never really had a top end mac for the time. Ive always had entry level performas. The last mac i had I got before I went to high school some time around 1996, and would somehow still be using that computer now had I not got this 867 G4.

    The thing is it would be nice to stably boost some speed out of this without spending any $$.

    Im trying to do this because, when you look at computers from a cost point of view, its much cheaper to build, or even buy, yourself a decent PC system and then have better resources on overclocking if indeed you wanted to do this. I can build a decent PC for the cost it takes to but a new processor card for this, and still be stuck with ancient memory and bus speeds.

    Apples have no info on overclocking. The people that do it(stock) are so limited and most info on it is rumor. Like this thing with having to use resistors instead of just jumping the damn registers.. how stupid(from a user's point of view). And if these systems are so picky as to malfunction if you use a resistor thats about 30 or so ohms +/- than the original one then ha.. gees dude. Apple DOSENT want you to overclock anything. .ever! Heh.

    But anyways. I prefer macs because, unlike windows XP (or messenger), they work. I, now, apparently, have made mine to where it seems to work okay for a long time then suprise me the next morning by not starting up. Its ok though. If this one craps out Ill just use my nasty old 466 Mhz P 2 NastyPc that I got for about $25 running out of a mountain dew box. Hehe. But id prefer to get this running so where it wont crash, at least to hold me out till i get enough $$ to get a newer mac, even an iMac. Those look very nice. But ever since even the betas of OSx, OSx has been just next to bulletproof. My computer crashed more in the past 2 days from my own doings than it has in the past 5 years that i had it. These computers are amazing, Im just looking for a little extra speed, as 1Ghz would be a great thing for me to tide me over until the next mac. Certainly, I can live without it, but I have a hard time bringing the speed back after ive just felt the hot speed of 1 Ghz.



    And seriously if anyone knows if you have to have something very, very close to 1000 ohms to jump these clock register contacts please post. Currently I upped the core voltage to 2.05 now to see if the crashes continue, but I still suspect it has something to do with the clock chip, not the volts chip.

  4. #4
    Join Date
    May 2001
    1hr N/W of LA LA Land


    You are in mostly uncharted waters my friend.

    While many of us here like to tinker a bit (my last main Mac was a Beige G3 desktop clocked to 466 running 10.3.9) we usually don't get as deep into it as you are. I don't know that I'd attempt soldering on a CPU daughtercard even though I can solder pretty good, and have a nice iron especially on my main machine without some kind of backup plan. Just the thought of having to use a PC would be enough to keep me from taking the risk.

    You could get some more resistors to see if you can get some that are closer to spec.

  5. #5
    Join Date
    Feb 2001
    on the landline, Mr. Smith


    Hi again,

    I agree with Randy, most around here probably won't be of help - though you never know. Lurkers....

    For really geeky hardware nuts, at the component level, you might try the forums at Mainly video card flashing, but some guys are soldiering ROM chips, parting out power supplies and the like. You might also ckeck over at too..... Several threads about overclocking minis which sound very similar to what you describe, so maybe one of the members can help with specs and sources. That's about the extent of Mac specific OCing forums that I am aware of.
    "Imagine if every Thursday your shoes exploded if you tied them the usual way. This happens to us all the time with computers, and nobody thinks of complaining." -- Jef Raskin

  6. #6
    Join Date
    Jan 2001
    Mobius Strip


    iTunes seems to be a good test of a system's RAM for one thing. Not all RAM is happy, but it helps to know what you are running. Every new update to OS X also seems to push thruput further. There is a program "DIMM First Aid" that runs in OS 9 that will tell what the RAM you have is as far as CAS latency, MHz and nanoseconds. A mix or wrong DIMM can lead to problems, especially if you try to boost a system.

    Tweaking the front side bus doesn't really work (the Beige had variable bus of 66-83MHz) but otherwise, no.

    The cpu upgrade database and over-clocking articles on is a good start. maybe just find a compatible cpu someone is selling that has upgraded theirs to faster Giga.

    you might enjoy and find some information in this thread: v2.1 7455 vs. v3.2 7455A - observations

    I would think you would have to dip into Freescales papers and articles, but tweaking an extra 50MHz, while it use to make sense, when systems were 400-450-500MHz and big cost difference, has marginal return.

    If you factor in software, the MacMini comes in as a nice little G4 1.6GHz system for $400 (plus $100 for memory). And your current G4 will still fetch $300 easily, depending on what you have.

    Caring for OS X does take some work and maintenance, like when you do crash, don't just let the journal replay, but run fsck first. And yes, 1GHz really helps, along with 1-1.5GB RAM. 7450's were not perfect, but you might find 933MHz or 1GHz cpu from Giga specials page, trade-ins resold by OWC and Small Dog.

  7. #7
    Join Date
    Aug 2000
    Concord, CA


    The original resistors, the tolerance band, do you recall the color? Good explanation here showing that it is possible to purchase 1 or 2%. Important tho to match physical size of the originals or slightly larger for heat dissipation watts or else they could fry.

    Where to buy 1 or 2%? Google search examples:

  8. #8
    Join Date
    Feb 2006


    Woa, cool. So many posts.

    I have a small belief that if the resistors used are close to 1000 (The original ones were more like 940 anyways) then it should trigger the clock chip to establish that register as closed, even though the resistor may be a lot closer to 900 ohm than 1000 ohm.... but.... then again im not sure about that.

    Plus, it could be my ohm guage too.. it might say 940 for 1000, wheras the original register resistors are very very close to 1000.

    I dunno, its all test and run. I wouldnt be bothered except for the random crashes.

    Granted, when I did the overclock, i went straight to 1Ghz and left the core voltage alone. Then, there were crashes and troubles relating to the L3 cache. a .05v boost took away half of the problems plus I saw the L3 cache all the time again in the About this mac window. Boosting another .05v seemed to take away the rest of the problems, except for some random crashes here and there. I just yesterday had a crash whilst chatting online and so i openned it up and boosted the core volts another .05 volts, so thats a grand total in theory of 2.05 volts, original being 1.90.

    So, perhaps the random crashes i had are eliminated with the last .05v boost. It hasnt crashed since i upped it the last .05v so ill see how this works.

    I would feel better with better resistors. The ones im using are HUGE compared to what I need. Theyre 5% tolerance with a gold resistance indication band, and theyre from radio shack. Theyre about half an inch long and maybe an 1/8 of an inch in diameter. The ones i had to painstakingly remove from the board were about 1x1.5x3mm. Haha. Very tiny.

    But if this last voltage uppage took care of the rest of the crashes then it can be assumed that 5% tolerance resistors are okay in that anything close to 1000 ohms will count as a closed register. Or, the lack of perfect resistors might be requiring the voltage to be higher to be stable.. I just dont know.

    Hm, i wonder what would happen if i just jumped it and didnt use resistors but i dunno if i want to do that. it definately would be easier though.

    The voltage chip seemed to be using resistors as jumpers too, but after trying to modify that thing I wasnt going to add resistors to that too to close the voltage registers. That was too tedious, and the resistors were maybe around 400 ohms.. so i dunno. Maybe theres a reason why ~400-500 ohm resistors were used for the volts registors instead of flat out jumpers.

    Its all trial and error for me at this point (well, it never really was anything definate ) but I hope that this last voltage thing fixed my problems because ive already taken out the processor card like 10 times and i dont think its good for it to be comming out and going in on a daily basis.

    Thanks for the replies! Ill check out some of those articles and forums. I didnt visit those before in my sparse-resulting search for mac Oc help. If anything happens new Ill post a message! Thanks again !

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