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Powermac 6100 won't boot with additional memory
Posted by: morrisonmuzk on 2026-08-02 15:56:09
Hi all...thanks in advance for reading!

Ok, so I've got a PowerMac 6100 that I recently recapped...I did the power supply and the logic board. Power supply is stable and meeting voltages.

I can always get it to chime, but I can only get it to get video and boot up if I remove any extra added memory from the 2 slots...it will only boot with the memory soldered on the logic board.

I've tried
  1. booting with and without pram battery
  2. swapping out the existing memory (at least the memory that was in it) and putting in different memory...always paired
Either way, I can only still get it to boot & video if I remove the extra memory (and have pram battery in).

I'm really stumped on this one...any thoughts or ideas? What am I missing?

thanks!
Posted by: killvore on 2026-08-04 06:24:28
Hey! Some quick control questions:
- do you know if adding RAM worked prior to the recap, or was the machine nonfunctional when you got it?
- does the RAM you are using work in other machines? Is it fast enough? (probably, the 6100 is not very demanding)
- how far along does the machine get with RAM installed - does it bong, do you get video, do you get a cursor, etc.
- are the RAM sockets clean? Did a blob of something fall in while you were recapping? Not sure if this would result in OK boot without chips, but failed boot with - but worth a quick check imo

(the PM6100 needs a battery to boot, like the LC475, so this is expected behavior and you can eliminate it as a variable imo)
Posted by: morrisonmuzk on 2026-08-04 09:03:26
It’s a a computer I got recently, so don;t know a ton about its history.
1 - I did get it to boot once prior to recapping. Memory that came with it was installed at that time, but it did take me awhile to get it to start…I don’t remember if I had PRAM battery in it at that time
2 - the ram was all tested before but been stored for years. I haven;t tried it in other machines …good idea!
3 - with ram installed I only get the bong…no video or anything else after that
4 - I’ll check the ram slots when I get home!

Thanks for taking the time!
Posted by: stepleton on 2026-08-05 00:23:29
I don’t remember if I had PRAM battery in it at that time
You must have done, since the 6100 will not boot without a working PRAM battery. It may show signs of life, but a normal boot needs a battery to be fitted.
Posted by: morrisonmuzk on 2026-08-10 10:25:38
Hey! Some quick control questions:
- do you know if adding RAM worked prior to the recap, or was the machine nonfunctional when you got it?
- does the RAM you are using work in other machines? Is it fast enough? (probably, the 6100 is not very demanding)
- how far along does the machine get with RAM installed - does it bong, do you get video, do you get a cursor, etc.
- are the RAM sockets clean? Did a blob of something fall in while you were recapping? Not sure if this would result in OK boot without chips, but failed boot with - but worth a quick check imo

(the PM6100 needs a battery to boot, like the LC475, so this is expected behavior and you can eliminate it as a variable imo)
Sorry for delay in the reply...son came home and had to put things off for awhile. Killvore, you had a great suggestion. I checked the ram slots and sure enough, in one of them, was the tiniest piece of solder. Pulled that out and machine booted right up as it should.

Thanks again for making me think and I'll do better in the future!
Posted by: killvore on 2026-08-10 10:57:25
Fantastic! I am relieved to hear that you got it working again 😄 celebrate with a painfully slow Bryce3D render!
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