6100 missing ROM

[mitchW]

My firend picked up a lot of old Macs that were sitting in a basement for last 10 years. Mostly from the 1991-98 era, including two Power Macs 6100.

I fired them up... and nothing! Then I realised that the ROM chips are missing in both, such a bummer.

Is there a way of getting them? On eBay, there are none. Can I use for example, a 7100 or 8100 ROM in a 6100?

Perhaps is there someone that makes new SIMM modules with ROM chips?

 

[Macdrone]

6100's have a rom slot but now card is required.

Do a power button "double tap" and if that does not work then try recapping.

Open it up also. If you have not pulled the pram batteries it may be too late.

 

[beachycove]

I have at least a couple spare, with 256k cache cards as well. Send me a PM if interested.

 

[Macdrone]

I meant no card is required sorry

 

[trag]

PM6100 definitely needs a ROM DIMM.  There were no models with soldered down ROM.   The ROMs used to be pretty common.

I recommend that you take BeachyCove up on his offer.  Failing that, Rob Spivey, Macmetex on Ebay, had some.  I don't if he still does.  I think their Apple part number is something like 341S0757 or maybe 343S0741.  

The 7100, 8100 and 9150 also require a ROM DIMM.

The machines will power up without a ROM(that's controlled by the ADB/CUDA controller) but they won't make any boot sounds or perform any functions.

Actually, these machines will power up with the CPU completely desoldered from the logic board. 

 

[mitchW]

Thanks. Yes, I will probably take the ROM from BeacyCove.

Now a question, is the ROM for 6100/66 any different from 6100/60AV? In that pile of old Macs we found working 6100/66 and I took it for testing purposes. I found out that 6100/66 boots and works, but the other one, a 6100/66AV model does not even chime with the ROM installed. Could the problem be in different ROM? Or perhaps the logic board is toast...

 

[trag]

There were a few variations on the ROM versions for that family of machines, but putting in the wrong ROM won't cause a failure to boot.  At most, you might get an unstable machine.  The revisions were pretty tiny and I don't think the 6100 ever got a revision.

It was the 8100 and 9150 that had slightly different ROMs supporting the variations in NuBus controllers and such. 

 

[trag]

Sorry for the repeat.  Apparaently I clicked repy instead of edit   New material a couple of paragraphs down.

There were a few variations on the ROM versions for that family of machines, but putting in the wrong ROM won't cause a failure to boot.  At most, you might get an unstable machine.  The revisions were pretty tiny and I don't think the 6100 ever got a revision.

It was the 8100 and 9150 that had slightly different ROMs supporting the variations in NuBus controllers and such. 

Is it possible you're moving the cache between machines, instead of the ROM?  Try booting the AV while you have the "ROM" out of it.

You can't rely on the slot labels.  The ROM and the cache DIMMs can go in either slot.  So you could have the ROM in the cache slot and vice versa.

 

[mitchW]

I know about the differences between the Cache DIMM and the ROM DIMM. The ROM DIMM has the Apple 341-0741 PN, cache does not, also the cache has 8 chips on DIMM, the ROM has only 4. So I know which is which

Yes, I changed both modules, also tried booting without Cache and with ROM in different slots, but I guess that the AV has bad logic board, since the CPU only gets slightly warm in 5 minutes, whilst the other one gets quite (normal) hot.

Also, the working one has a 820-0556-B revision logic board, the dead one has 820-0539-B, possibly any differences?

 

[trag]

I know about the differences between the Cache DIMM and the ROM DIMM. The ROM DIMM has the Apple 341-0741 PN, cache does not, also the cache has 8 chips on DIMM, the ROM has only 4. So I know which is which

Yes, I changed both modules, also tried booting without Cache and with ROM in different slots, but I guess that the AV has bad logic board, since the CPU only gets slightly warm in 5 minutes, whilst the other one gets quite (normal) hot.

Also, the working one has a 820-0556-B revision logic board, the dead one has 820-0539-B, possibly any differences?

Yep, it definitely sounds like something is amiss with the AV board.   My understanding is that you have two complete machines, except for the ROM.  Have you tried swapping the power supplies?   The problem could lie with the PS instead of the logic board, especially if the CPU is not getting warm.   Those PPC601s seemed to get warm no matter what.

Do you have something in the PDS slot of both logic boards?  If there is no video card or expansion board in the PDS slot, then there needs to be a PDS terminator board in the PDS slot. 

If neither of the above yields fruit, try (carefully) removing the heat sink from the problem-6100.   Examine the CPU to see if it is cracked.  I've seen a lot of 6100, 7100 and some 8100s with cracked CPUs...

While you have the heat sink off, clean the old heat sink grease (may be more of a powder by now) with alcohol, being careful not to rub the grease onto the CPU pins.   Add a dab (a tiny dab) of fresh heat sink grease and replace the heat sink.  A "tiny dab" because you don't want to put so much on there that it runs off the center of the die and out onto the pins of the CPU.   I killed a Power Computing Power 120 (8100 clone) that way once.

Oh, while testing, remove all RAM from the machine.  There's 8MB on the logic board.  That's enough to get a startup bong.

An old memory also says that the 6100 won't generate video at start-up without a good PRAM battery, but I'm not sure whether I'm confusing it with other pizza box models.

 

[mitchW]

I actually put the two machines in the same state, removed all of the RAM, ROMs and Cache modules and floppy drives and turned them both on. The AV one CPU didn't get warm. Swapping the PSUs did nothing.

Actually the PDS slot is empty in the both machines, but that doesn't stop the 66 one to work, perhaps the AV needs the terminator?

I'll check the CPU if it's cracked. You are right about the PRAM battery, as without it, it won't output the picture.

 

[trag]

You have good testing methodology.  Not everyone does so it's usually worth suggesting if it has not already been specified.

I suspect that the PDS terminator requirement could vary from machine to machine, even within the exact same model.   Apple's specifications say that something must be there to terminate the bus.   In reality, the lack of a card may not cause enough ringing on the bus to cause a problem, in some cases.   But in other cases it probably does, because if it did not, it seems unlikely that Apple would have gone to the trouble to fabricate and include PDS terminator cards.   Power Computing included the terminators with their 8100 clones as well.

So, yes, I'd try terminating the PDS slot with some kind of compatible card and see if that makes a difference.   It that doesn't work, then check the CPU for cracks and try replacing the heat sink grease if the CPU isn't cracked.