Hi,

please, I have question to Mac Mini G4 owners.
Do MorphOS show CPU temperature with Thermal screenbar module?
And Mac OSX ?

Because MPC 7447A and 7447B in Mac Mini had thermal diode.

thanks!

No, MOS does'nt show any temp on Minis. OSX will do, I think.
You can see CPU-temp and FAN-speed in Open Firmware by typing
Code:

many thanks!

it is a pitty, I want to overclock mini a little , and there is no enough space for external measuring.
Maybe I install OSX instead of MorphOS for testing.

.status worked fine, but in OF CPU is practically idle.
Is there a way how read this from MOS?
Or how to utilize CPU to 100% in Open Firmware?

All my minis are overclocked from 1.25 to 1.42 Ghz without problems

I have mini 1.5 GHz with 7447B CPU. And I overclocked it to 1.83 GHz. 7447B is capable of it.
CPU is going fine, no lockups or errors, but I want made some long-term stress test.

When I overclocked something, I often replace cooler for more powerful and measure the temperature. Mini have no space for it.

So I want measure the temperature during testing, from OS or OF.
And of course, during daily use of MorphOS it will be super.

In that case you will do it with OSX, I think.......

Btw: Since MOS 3.14 a new recource (nvram.resource) was added, which can be used to read/write Mac's NVRAM. For example this is used to reduce startup-chime-loudness (which, btw, does'nt work on Mini). So theoretically its possible to read out CPU-Temp. But I doubt that anyone writes a prog to do that.......

> Since MOS 3.14 a new recource (nvram.resource) was added

Wasn't this 3.12 already?

"Resource for reading / writing the NVRAM on Mac computers."
https://www.morphos-team.net/releasenotes/3.12

Maybe......

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No, the Mac mini thermal sensor is not related to the nvram at all, nvram just stores various setup/config values.

The startup-chime on Mac mini can either be turned off completely or turned on. Mac mini has no H/W to control audio volume. At least setting it to 0 or non-zero works fine on my 10,1 mini to disable/enable it.

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Some years back I did some test tool to read the sensor values on Mac mini via MorphOS. The temperature sensor is basically behind some microcontroller which automatically controls the fan once action is required, so I never bothered to integrate it as part of MorphOS sensors. This is opposed to other Apple systems which need active software control to adjust fan speeds.
It also had some impact on system performance if it was repeatly reading the sensor values the way it was implemented back then, so it did not make it into MorphOS directly.

You can give it a try if you like

Mac mini temperature sensor shell tool

Let me know if it works for you ...

Quote:
Thanks, this is very useful information. It means that if fan has not 100% RPM, CPU is not so hot.

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Many thanks! I will let you know for sure. If all will be OK, maybe I write a little article.

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Thank you for clarification.
Startup-chime works, as you discribed, here too....

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@cyfm
Many thanks!!!
It is exact the thing! I tested my overclocked Mini with infinite loop of DhrystoneV2PPC and pmu_max6642-read.

Temperateure rises to 54°C and then fans start to increase RPM and temperature never exceeds 56°C.
Many thanks for this tool!

First iteration:
Code:

Following temperarure results:
Code:

And than temperature of reg00 (what should be core I think) oscilates between 53-56°C.
It looks safe to overclock MPC7447B to 1.83GHz with original cooler.

[ Edited by sailor 23.04.2022 - 11:44 ]

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Ok, great to hear that the tool is of some use for you.
In OpenFirmware, the local sensor is labeled 'CPU bottom site' while the external/remote one is 'CPU on die', so I guess that is where the actual measurements take place ...

I wonder if "on die" means thermal diode inside CPU.
Becouse in this case is I suppose that 'CPU bottom site' <= 'CPU on die'.

But in any case temperatures are low with enough reserve for unsure place of sensor.

Anyway, pmu_max6642-read is super utility.

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Well, "on die" actually means that the external temperature measured is the value directly received from the MPC7447A PPC CPU which has an "on die" temperature diode:
MPC7447A datasheet

Local temperature bottom side is directly measured by the MAX6642 temperature sensor which I don't really know it's location of on the logic board but it most likely measures more of the ambient temperature. As the "northbridge" and GPU are both located on the opposite side of the logic board, it might be somewhere around there.
Why the "core" temperature is somewhat lower than the actual "ambient" temperature is something I don't really know.

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It is a little bit strange, but with temperature around 55°C on CPU thermal diode there is enough reserve for (for example) not exact calibration, etc.

Before overclocking of my Mini I read the forums and there is often opinion that Mini have much bigger problem with cooling of GPU than CPU.

MPC7447A HW spec I read before overclocking. But I cannot find anywhere MPC7447B
So for simplification I assumed, that only difference was higher Maximum Rated
Core Frequency - maybe 1.5 - 1.67 GHz

This overclocking was the most risky I did. Without exact CPU documentation and without possibility of better cooling. Not to say the PLL config pins and rezistors on Mac Mini are really microscopic.
Only thing that calmed me down was your temperature utility.

I've read on the internet ( believe everything you read! :) ) - that the iMac G5 can also be "overclocked" by moving a transistor from one place to another and making the bus speed run at 1/2 instead of the normal 1/3.

Edit : Found it - https://www.reddit.com/r/overclocking/comments/28t1gl/overclock_imac_g5_bus_speed/

Has anyone tried this?

[ Edited by MoerBoer 25.04.2022 - 12:54 ]

@MoerBoer

I am not sure that things here are so simple.

Normally (and with G5 too) you set the CPU speed by known System Bus speed and proper PLL setting (i.e. multiplier)
Then CPU speed = Bus speed x multiplier

Note: G5 have a little different PLL tables nomenclature, instead of "multiplier" uses "Ratio". But it is generally the same number. Ratio 3:1 = multiplier x3.

In case of iMac G5 (I assumed here 2.1 GHz, model is not mentioned in your link) we have 700 MHz Bus, and CPU 2.1 GHz, i.e. multiplier x3 (Ratio 3:1)

If you want change Bus speed to 1.05 GHz, you have to: Change Bus speed to 1.05 GHz somehow and change multiplier to x2 (ratio to 2:1).
I wonder if this should be done by change of two resistors. But who knows.

Not to say, that from System bus speed are often derived other speeds (RAM) and Northbridge also have his own frequency limit.

I never overclocked G5, because the overclocking scale is very rough.
Is OK with G4 change multiplier from x9 to x10.5 with System bus 133 or 166 MHz, but the G5 case is x3 or x2, it is 50% difference in frequency! And Bus speed increase in your case from 700 MHz to 1.05 GHz is also 50% step up.

In any case, if somebody want to try it, I recommend at first check iMac G5 Northbridge max frequency, probably change RAM stick to higher speed (but here is also RAM onboard and it can be showstop).
And first of all proof from other sources what exactly are R3012 and R3028 rezistors and how the frequency logic works in iMac G5.





[ Edited by sailor 25.04.2022 - 13:37 ]

@sailor

Thank you for the very informative post and yes, I have the 2.1GHz model.

I won't be doing any soldering on my baby, just thought it was an interesting post, but your information makes sense that this is not as straight forward as it looks.

In G5 models BUS-speed is bound to CPUSpeed (ratio), which is coded into CPU-module.
On a PowerMacG5 1,8GHz you have Bus-speed of half (900MHz). Changeing the CPU-Modules to a 2,3GHz-version, rises up BUS-Speed to 1150MHz automaticaly (Northbridge can do that - working on such a G5 at moment).

So its more a issue of the CPU than of Northbridge.

In iMac there are no CPU module. But of course, it can be done similar way.

But with quick search on web I found, that Front Side Bus (Processor Interface Bus) frequency on block diagrams is 667 MHz for iMac iSight and 600 MHz for older iMacs.

I don't think it will works with 1.05 GHz, but everything is possible. Only me will not do it with my iMac.

But if somebody want to try search for bus overclocking, good start are Northbridges:
Powermac G5 PCI-X have U3
Powermac G5 PCIe U4 (= IBM CPC945)
iMac AGP U3 Lite
iMac iSight some other

Isn't it 700MHz bus as it's running at 1/3 for 2.1GHz?

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Can you provide benches (numbers and subjective experience to decide wether this overclocking is worthwhile for everday usage or just for the geek factor (which of course is a pretty strong and valid point!).

Most interesting (for me): you also have an iMac G5 (as have I), how does the overclocked Mini compete with the iMac (I myself wonder how close the iMac G5 and the 1.5 Mini are, some parts - for example jpg decoding is faster on the Mini compared to the iMac, but Wayfarer is a good share faster on the iMac).

> MPC7447A HW spec I read before overclocking. But I cannot find anywhere
> MPC7447B ;-) So for simplification I assumed, that only difference was
> higher Maximum Rated Core Frequency - maybe 1.5 - 1.67 GHz ;-)

I don't know what the specific difference is between 7447A and 7447B/C, but it's not the maximum rated core frequency as there have been 7447A chips rated at 1.7 GHz, like the MC7447AHX1700PC (see Freescale/NXP PDF linked there).