IBM 6160 wont boot with memory expansion installed.

[darrylo]

I have a 5160 I'm busy restoring with a strange issue.

It works 100% fine with its on-board 256k ram. If I install any of my 3 known good memory expansion cards it gives me a non system disk error on the A and C drives.
It counts up the extra ram fine with no errors.
I have no idea where to start with this.

 

[sergioag]

It works 100% fine with its on-board 256k ram. If I install any of my 3 known good memory expansion cards it gives me a non system disk error on the A and C drives.
It counts up the extra ram fine with no errors.
I have no idea where to start with this.

Can you provide these details:
- Which card are in the system?
- In which slots are they?

 

[darrylo]

Can you provide these details:
- Which card are in the system?
- In which slots are they?

Six pak plus
Ibm 256k card (dip packaged)
Ibm 256k card (old square silver packages)

I just tried the 3 cards in my 5155 and they work. It's also the same 5160 256k motherboard

 

[darrylo]

Six pak plus
Ibm 256k card (dip packaged)
Ibm 256k card (old square silver packages)

I just tried the 3 cards in my 5155 and they work. It's also the same 5160 256k motherboard

The board I have is the one with the bodge wires like this one. https://minuszerodegrees.net/patch_wires/5160_motherboard_with_patch_wires_1.jpg

 

[sergioag]

Six pak plus
Ibm 256k card (dip packaged)
Ibm 256k card (old square silver packages)

I just tried the 3 cards in my 5155 and they work. It's also the same 5160 256k motherboard

In which slot are they inserted? Also, which other cards are you using? Specially the FDC and, if you're using one, any hard disk controller.
Remember that slot 8 is special and shouldn't be used unless the card specifically supports it and it's jumpered as it should be for slot 8.

 

[darrylo]

In which slot are they inserted? Also, which other cards are you using? Specially the FDC and, if you're using one, any hard disk controller.
Remember that slot 8 is special and shouldn't be used unless the card specifically supports it and it's jumpered as it should be for slot 8.

I am aware of the slot 8 issue. I am using the standard IBM FD controller (later version) and IBM MFM controller with type 13 drive.
What I did notice, if I insert a floppy it tries to boot but makes a terrible sound.
DMA or IRQ conflict ? cant imaginer how as my 5155 is so similar.

 

[modem7]

It counts up the extra ram fine with no errors.

Confidence that 'RAM overlapping', like the example shown in the diagram at [here], is not happening.

Six pak plus
Ibm 256k card (dip packaged)
Ibm 256k card (old square silver packages)

"Ibm 256k card (dip packaged)" --> IBM 64/256KB Memory Expansion Option
"Ibm 256k card (old square silver packages)" -->IBM 256KB Memory Expansion Option

DMA or IRQ conflict ? cant imaginer how as my 5155 is so similar.

If we look at the case of the 'IBM 64/256KB Memory Expansion Option' as an example, that card contains only RAM functionality, and therefore, cannot create a DMA or IRQ conflict, because such a card (RAM functionality only) does not use DMA nor any IRQ's. The DMA/IRQ related fingers on the ISA edge connector either don't exist, or if they exist, are not connected to any circuitry on the card.

I just tried the 3 cards in my 5155 and they work. It's also the same 5160 256k motherboard

Suggesting something wrong with the subject 5160 motherboard.

This might be a RAM addressing fault in the motherboard. The POST in the IBM BIOS ROM will detect some cases of RAM addressing faults, but not all. Do you have the ability to create a Ruud's Diagnostic ROM (RDR)? RDR will detect a lot more cases of a RAM addressing fault.

 

[darrylo]

Confidence that 'RAM overlapping', like the example shown in the diagram at [here], is not happening.

The motherboard switches are set for the 256k onboard. The starting address of the Six Pak is 256k. Same setup in the other system works.

"Ibm 256k card (dip packaged)" --> IBM 64/256KB Memory Expansion Option
"Ibm 256k card (old square silver packages)" -->IBM 256KB Memory Expansion Option

That is the correct cards.

If we look at the case of the 'IBM 64/256KB Memory Expansion Option' as an example, that card contains only RAM functionality, and therefore, cannot create a DMA or IRQ conflict, because such a card (RAM functionality only) does not use DMA nor any IRQ's. The DMA/IRQ related fingers on the ISA edge connector either don't exist, or if they exist, are not connected to any circuitry on the card.

The motherboard switches are set for the 256k onboard. The starting address of the Six Pak is 256k. Same setup in the other system works.

x

Suggesting something wrong with the subject 5160 motherboard.

This might be a RAM addressing fault in the motherboard. The POST in the IBM BIOS ROM will detect some cases of RAM addressing faults, but not all. Do you have the ability to create a Ruud's Diagnostic ROM (RDR)? RDR will detect a lot more cases of a RAM addressing fault.

I suspect this is the case, I unfortunately don't have the setup to burn roms. will have to look to purchase.

A new development is that I get it to boot the IBM Diagnostic disk from floppy. It even runs all tests.

 

[darrylo]

I went back to basics. Did a thorough visual inspection. I did notice that the previous owner replace the 12v tantalum caps.

What I didn't notice is he forgot to replace 5 of them. The 3 of the 4 that run between the ram chips and 2 between the isa slots.

If the ram uses 5v and -5v the missing caps shod have no effect on the on-board ram. Maybe it's enough to interfere with the cards ?

 

[modem7]

What I didn't notice is he forgot to replace 5 of them. The 3 of the 4 that run between the ram chips and 2 between the isa slots.

Per the photo at [here], those capacitors are all on the +5V line.

If the ram uses 5v and -5v the missing caps shod have no effect on the on-board ram. Maybe it's enough to interfere with the cards ?

The RAM chips on the 5160's motherboard only use a +5V power source.

There is inadequate filtering of the +5V line on the motherboard. Plugging in a power-hungry ISA card makes the filtering situation worse. You need to replace the missing capacitors.