Searched your serial number @ https://appleserialnumberinfo.com/Desktop/index.php and came up with this:



Then searched same with EveryMac.com and it returned this info:

     

And for more detailed info on your MDD (like RAM specs, basic OS, etc.) check out:
https://everymac.com/systems/apple/powermac_g4/specs/powermac_g4_1.25_dp_mdd.html

And which RAM slot do you have the single 512 mb stick in? If it is not in J20, try also in other slots.
You might even try other RAM sticks in other slots, leaving the J20 slot empty. For more info see:
https://macos9lives.com/smforum/index.php?topic=7637.msg59231#msg59231

Or read that entire topic, beginning here:
https://macos9lives.com/smforum/index.php?topic=7637.msg59178#msg59178

Sure you might have a failing CPU or a damaged mobo but for the machine to only allow one stick of RAM,
well maybe you have the J20 slot problem too? If the single stick works in J21, J22 and J23, leave the J20
slot open and then test (one at a time) two other sticks along with the known working stick to see if it might
work with two or three sticks, total. (With the J20 slot left open.)

And maybe you’ve got mixed & matched RAM? PC2100 DDR and PC2700 DDR?

[I’m now going to bed!]

If you photograph the CPU, do please also photograph the entire open view of the mobo too.

AND I’ve sent you a PM. (In case you have not noticed it). Check “Messages” at top of opening page.

Cheers!

Quote from: aBc on September 20, 2025, 09:25:01 PM

The ONLY thing that I might even remotely question is the “3-4 users” estimate of those “heavily into gaming and or animation”. Thinking that there are far more gamers around here now than we might suspect.

Sorry… I meant the 3 or 4 into heavy animation using an MDD as we're discussing here. There are quite clearly a lot of vintage gamers playing with vintage Macs of all kinds.

My apologies Gary. Was just needling you a bit and I should have included a smiley there.
Actually referring to an excellent post by you, adding so much more insight to the topic.
Thanks!

I think you have arrived at the most likely conclusion.

The lesson here is that BU drives are sacred devices that should be labeled and securely stored unless/until you are absolutely certain you will never need anything they contain. If you reuse one, initialize it first.

I can afford any measures apart from replacing motherboard and daughterboard as in my country i am never finding replacement parts due to low amount of mdd sold there

Also when i replaced gpu with mx 2 400 with dead vram chip it had same symptoms apar from dvi thing

Tommorow i can remove paste and send pic of cpu

Thank you for confirming that the Mac wouldn't do this by itself.

I've been digging and looking at folder dates etc. The conclusion I've reached is I must have backed up some of my folders to this drive at some point and forgotten about it!

 

No idea why, but it's the only thing I can think of.

Congratulations. I've been using Macs literally for decades all the way back to the little Mac Plus and you have managed to come up with a problem I've never heard of!
I too, have a G4 with multiple drives specifically for system/apps and audio/data etc. I cannot imagine how this is happening to you.

Seriously… this would require guessing out of the box. Stuff like:
1) Somehow both drives have the same ID# ?
2) You used a foreign IDE ribbon cable?
3) One or both drives already had System and App files before you installed it/them in the machine and you only just now noticed?

When you "set up" a computer, you normally start with blank drives. AFAIK, there is no way your Mac would write duplicate files in two locations.
So, more info is needed here. What model G4? How did you set it up beyond “sticking in” two drives?

When i do exactly that it shut downs, same thing with of command

Not good.

Too bad you’ve no other MDD mobo to test with the ATX.

And without visual comparison of the two processors — can’t tell if one has been heated more than the other… in which case, one of them has possibly failed or is failing. There’s also the possibility that the daughtercard itself may be warped and not making full, adequate contact(s). [We’ve seen that before.]

*Applying direct, downward pressure on the heatsink (with the palm of your hand) might provide different results?

When you cleaned off the old heatsink paste before repasting, what condition was it in? Totally baked? And you don’t remember if one processor appeared different; as if it had been overheated?

Easier to remove the CPU and visual check. And easier to replace the CPU, rather than to pull and replace the mobo.

So if you go to the… time, trouble and expense of replacing the motherboard and then discover no change, you’d need to then possibly replace the CPU.

In the meantime, you can very closely inspect the mobo (top and bottom) looking for any signs of overheating or other possible damage to the myriad of tiny electronic components and traces.

So, if the ATX PSU is okay and functioning properly, I’d suspect the CPU and / or the motherboard at this point. However, the questionable GPU may be the root of your problem. And maybe after its replacement, conditions might change?

BUT with that processor warning… well, who knows?

Sorry, no quick-fix easy answers for you. Maybe I’m missing something, but as always… not easy to diagnose problems without the advantage of having machines close at hand.

If you’ve already ordered the new GPU, please report back if any change after installation.

Too many variables at this point.

When i do exactly that it shut downs, same thing with of command