Hitachi NV-RAM Incompatability Issue

[Jared]

Ran into a strange event today that doesn't make sense to me. Had a HTS547575A9E384 come in that had a burnt out PCB. I wasn't able to read the NV-RAM through the utility as it wouldn't come ready, so I physically moved the chip. The recovery went perfectly, read every last sector.

Now I just want to make my donor work again. So I tried writing the NV-RAM back to it. It acts like it writes fine, but it just won't work. I checked and both NV-RAM images are the same size. I even had two copies that I made of the donor and I've tried both, but to no avail. It's almost like the NV-RAM image of the donor isn't compatible with the chip (which I know is good, it still works on the patient drive).

Or is there something I'm missing that's preventing it from writing to the chip? Any thoughts.

(Oh and I seem to have lost the original chip from the donor, so that isn't an option at this point)

 

[Jared]

Edit: I actually just realized that it's not even spinning up after I write the original NV-RAM to it. So it must be that I either didn't get a good read (either time) or that the code is somehow not compatible with the NV-RAM chip. How strange.

 

[Jared]

Update: I managed to find the original NV-RAM. Soldered it back on, and it's working like a charm. How strange that the other NV-RAM chip worked to read the original drive with this PCB, but wouldn't even try to spin up with the other NV-RAM code. I guess you can't assume that these chips are always compatible to just write the code and not transfer the actual chip.

I guess I learned something new.

 

[lcoughey]

Perhaps the NVRAM contains info about the head pre-amp that prevents it from spinning if it detects that it isn't compatible?

 

[Jared]

Perhaps. I even tried writing a half dozen other NV-RAM codes from the same model to it, and none would spin up except the one from the original patient drive.

 

[Jono]

On really old Hitachi 3.5 drives, sometimes swapping PCBs would change a flag in EEPROM and the board wouldn't let the motor spin up.

 

[Jared]

It's just strange to me that using the exact same PCB (which works on both drives) the NV-RAM works when physically transferred but not when digitally transferred. The only explanation is the actual NV-RAM chip is somehow different and makes it in-compatible. It's making me think that you can't always trust just digitally writing the NV-RAM to the PCB on these Hitachi but that sometimes you'll need to physically transplant it.

Just something odd I thought I'd share.