PC-3000 Forum

Yesterday I was working with a drive that had a PCB electrical fault (Shorted 5v diode and blown fuses). After a rom swap to a known good pcb I was getting boot code CRC errors on the terminal. Only a partial rom read was possible.

I was able to read roughly 1/4 of the rom's contents. The rom size is 0x080000 (4mbit) and the read region is 0x020000 - 0x040000.
From what I can tell, IAP is at 0x000250, RAP is at 0x01B0C8, CAP is at 0x0244D8 and SAP is at 0x0246E8.
I can obtain CAP and SAP in full but the start of the RAP is cut off and the IAP is entirely missing.

Are the CAP and SAP adaptives enough for data access? I think the RAP is pretty important for data access too right?

CAP and IAP are usually not important
SAP and RAP are
The beginning of RAP contains serpentine formula for each head, so you can't just get it from any drive

I'm curious now. Would it be possible to work out the correct serpentine formula? Would that be the only need mandatory in the RAP?

I believe the ROM received too much voltage as the original PCB is showing 2.8v at the pads. The rom ( Winbond 25Q40BW ) is rated at 1.95v max supply voltage. Are there any tricks I could try to get the rest of the rom to read?

I am missing the first 20280 bytes of the RAP and have the last 4098 bytes by the looks of it.

It is actually possible to rebuild a damaged RAP file. It is tricky but it is indeed possible to do it. A coworker and I are in the process of testing and documenting a process for doing this. When we have a bit more testing completed we plan on sharing our research with the DR community.

Stay tuned....

Fraser

Fraser Corrance wrote:Source of the post It is actually possible to rebuild a damaged RAP file. It is tricky but it is indeed possible to do it. A coworker and I are in the process of testing and documenting a process for doing this. When we have a bit more testing completed we plan on sharing our research with the DR community.

Stay tuned....

Fraser

WOW ! This will be quite cool !

Looking forward to read more about this research !