Discussion Reducing wiring of the 24-pin connector

[Petri Krohn]

@Petri Krohn - have you got any work log or pics of your Mac hacks? Would be interested to see / read more about them

tonymacx86.com was down yesterday. Today it is online, but images do not display. You can however open each linked image in a separate tab.

This post is from 2016 about the PSU mod and Power Good signal. (Many photos) The method I used to de-pin the Mini Fit Jr. connectors is pushing two straightened staples into the connector housing. The part relevant to this discussion is in the end.

G5 power supply mod (help)
Faking Power Good
I tried different ways of faking the PG signal: connection directly to 5 volts or putting a 1 kiloohm resistor in between. All produced equally bad or good results. It turns out that the Intel desktop board did not care about the PG signal. Evidently it generates its own "power good" signal on the motherboard.

My Gigabyte GA-EG41MFT-US2H motherboard produced the opposite result. If I try to fake the PG signal by connecting pin 8 to 5 volts, the motherboard would start power cycling, turning the PSU on and off twice every second. It is however possible to boot the computer by pulling pin 8 to 5 volts at any time after power on with the CPU fan already spinning.

In the end I did not get my motherboard to start without some external start button, so I semi-abandoned the project. Two years later I bought an Intel Desktop board, which I guessed right, did not need PWR_OK. It is still in daily use with a Xeon E3-1230 v2. This post has a photo of the half-finished result. The board I used is the Intel® Desktop Board DQ77MK, which is similar to the Dell OptiPlex motherboard discussed in the thread.

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