MDD 866 Mods

[supernova777]

Seeing G4 kicking the ass of intel proc. is fun

well enjoy - because u will never see it again lol

[coachla]

This is an easy mod. 1.0ghz/167mhz is a huge benefit in OS9. I've done it on two 867's. Regarding fans... Scrap and kiss good-bye to that power connector to the MOBO, as it's that which causes the awful RF in the builtin audio and the whole wind-tunnel problem. I run just one fan atop the heatsink at 7 volts directly from the drive source (+5 & +12 = 7 volts), and the power supply has one of the fans removed for better air flow. No other fans. No need to use a soldering iron. You can snip the resisters off, which pulverizes the resisters, but who cares? The resisters for the 133 and 167 busses are reversed on Macbidule's translated page. You need to remove, not add, one to get a 167 bus. This was a French > English translation mistake. To go from 867/133 to 1000/167 you need only remove resistors.

[geforceg4]

interesting. i had an 867 that i got rid of. i wish i hadnt now!
is there any place where this is more clearly documented?
it seems like a very careful modification only for the expert + brave people

[Image.Material]

I can see this topic hasn't been updated for ages, but if anyone ever seeks this info:

I can confirm that the 1.0ghz single-processor PowerMac 3,6 (FW800) also supports the r676 removal to overclock the FSB from 133 to 166Mhz mod. You should just be even more careful for the fact that the resistor layout differs slightly from the 2002 MDD.

I have done it with my FW800 MDD and as soon as you put a multiprocessor daughtercard, the FSB is recognized as a 166Mhz one.

[Jakl]

Yes very true - I installed a dual 1.42ghz dual CPU daughter card onto this board and is what I am using to write this message here. Runs beautifully all the time.

One thing I do use for cooling this machine now that I never did earlier was the altering of the info plist file of the AppleFan.kext to alter when the main MDD fan is to kick in - this keeps the CPU temp around the 49ºC mark under heavy loads. I understand that by doing this it may cut fan life down but the machine never gets beyond the 50ºC mark ever. This seems to only work for TIGER - macOSX10.4.11 PPC.

[MacOS Plus]

  I presume the same bus speed mod is also possible on the Xserve Rev.1 motherboard - anyone have details for that?

[Image.Material]

I'm not convinced the Xserve can have its FSB overclocked.

As far as i know, the original Xserve was introduced a couple months before the 2002 MDD, and the OEM hardware configurations ( SP and MP ) all had 133Mhz FSB.

[MacTron]

I'm not convinced the Xserve can have its FSB overclocked.

It's not an overclocked bus.
There is two models of DDR xServe G4:

A) A 133 Mhz System bus and ATA 100 Hard disk Interfaces and FW400.
B) A 166 Mhz System bus and ATA 133 Hard disk Interfaces and FW800.

But the FSB can be overclocked from 166Mhz to 172 Mhz.
Probably both procedures are similar to the ones performed in MDDs

[Image.Material]

I'm not convinced the Xserve can have its FSB overclocked.

It's not an overclocked bus.

I meant overclocked as in "Overclocked from Apple's stock config", not pushing beyond the 7455's specs.

To be honest, I never saw an Xserve G4 (or even a RackMac) in front of me; even though I know they use the same board design as the MDD's, I'm completely unfamiliar with these.

I just noticed that there were machines that had onboard ATA-7 

[Protools5LEGuy]

Last sunday I went 30 Km away from my city to pick a broken MDD. It was a Uni 1.25 GHz MDD with SAMSUNG PSU (broken I guess) and a Radeon 9000 and a Sonnet Allegro FW400 ( probably with onboard broken firewire ).

I went to everymac and compared geekbench 2 results of 867 Dual Vs Uni 1.25 and were the same! For Mac OS X there is no advantage one machine vs the other. But on Mac OS 9 M.A.R.L. and other cultist would choose the 1.25.

So I decided to put the 166 and 1.25 on the 867 dual box that has a working AcBel PSU.

Notice the colour greener on 133 and bluer on 166

[Protools5LEGuy]

The boards are different. So I decided to take use on my new phone and take some pictures of the R676 on the back side of the motherboard to kill the subject at last.

[Protools5LEGuy]

On the CPU Daughtherboard side:

I could find R22, R26 and R27 on the front of the Dual 867, and I couldnt find R22 on the front or back of the Uni 1.25.

I could find R26 and R27 on the back side of the Uni 1.25

[Protools5LEGuy]

Just in case someone want to find R22 (maybe is not needed)

[Gaz]

Question : I have a working 866 DP , and a broken 1.2 DP, may I swap the Cpu? Can it cause problems with the bus speed? In theory the cpu will be underclocked due to the slower bus clock, other downsides?

[Gaz]

Ok the CPU swap worked! Now I have a dual processor @ 1ghz . The slower bus resulted in a underclocked CPU (1Ghz vs 1.25) but for me is now enough, not in the mood to risk damaging the hw overclocking!