Access Disk On Chip?

[goontron]

I have a 64mb Disk on chip that i need to write to.. Im at a loss as how to access it. Does anyone have experiance with these things?

[Spork Schivago]

Re: Access Disk On Chip?

Is this the chip you're talking about?

https://cdn.badcaps-static.com/pdfs/...d4b6dda795.pdf

If so, I know this probably isn't the best solution, but someone on another site had some good ideas.

http://www.electro-tech-online.com/t...module.112240/


They found if you had an old ISA network card that supported a boot ROM, you could insert the DOC into the socket, boot off the card and it'd let you access the data on the chip as a hard drive. Maybe someone else with more knowledge could chime in before you try it though. I'd hate to suggest something that might actually ruin your DiskOnChip.

[goontron]

Re: Access Disk On Chip?

If itll work in a bootrom setup in a sound card, it should work on a NICs boot ROM socket too! Genius! Ill give it a try!

[Spork Schivago]

Re: Access Disk On Chip?

If itll work in a bootrom setup in a sound card, it should work on a NICs boot ROM socket too! Genius! Ill give it a try!

I didn't come up with the idea, I just found it for you. Please let me know if it works. I'm kind of interested what type of stuff might be on that little card there.

I wasn't sure if you just wanted to access it or if you wanted to use it in your own circuit board and access it that way. I hope it works out well for you.

[fzabkar]

Re: Access Disk On Chip?

I'm very interested in the outcome of this thread. I was involved in a data recovery from a DOC with a corrupt NAND chip (inaccessible via DOS), but that involved removing the physical memory chip and dumping its contents in a reader. Hopefully your DOC is fully functional, otherwise I have written a program to restore the file system from a raw NAND dump.

There are some DOC tools which can read and program the DOC, if it is functional.

[Spork Schivago]

Re: Access Disk On Chip?

Did you have any luck Goontron?

[goontron]

Re: Access Disk On Chip?

^ Don't have access to the NIC till saturday...

[TechGeek]

Re: Access Disk On Chip?

And it's Saturday.

[Spork Schivago]

Re: Access Disk On Chip?

Seems like we have a couple people interested in the outcome here Goontron!

[goontron]

Re: Access Disk On Chip?

outcome was: Cant find the blasted card!

[TechGeek]

Re: Access Disk On Chip?

Hahahahahahahahahahahaha!!!!!!!

[goontron]

Re: Access Disk On Chip?

I wonder if I slot it into the BIOS ROM socket of my 386 after it is booted, if it'll work.

[TechGeek]

Re: Access Disk On Chip?

No, the system will probably lockup as soon as you remove the BIOS ROM.

[kaboom]

Re: Access Disk On Chip?

I wonder if I slot it into the BIOS ROM socket of my 386 after it is booted, if it'll work.

Catch-22 with those older systems:

Yes, you can shadow/cache the BIOS rom image to RAM, so calls no longer go to the physical ROM IC, but:

Those older systems commonly used an EPROM, not an EEPROM to hold the BIOS program.

(Erasable programmable ROM vs electrically erasable programmable ROM.)

That means no in-system-programming on most (all?) 386 mobos. Flash (EEPROM) didn't become common til late 486/early Pentium MBs. I would not assume a 386 MB's EPROM socket is even wired for such ISP'ing.

[goontron]

Re: Access Disk On Chip?

Catch-22 with those older systems:

Yes, you can shadow/cache the BIOS rom image to RAM, so calls no longer go to the physical ROM IC, but:

Those older systems commonly used an EPROM, not an EEPROM to hold the BIOS program.

(Erasable programmable ROM vs electrically erasable programmable ROM.)

That means no in-system-programming on most (all?) 386 mobos. Flash (EEPROM) didn't become common til late 486/early Pentium MBs. I would not assume a 386 MB's EPROM socket is even wired for such ISP'ing.

all i need to do is dump it to examine where the corruption is...

[kaboom]

Re: Access Disk On Chip?

all i need to do is dump it to examine where the corruption is...

You can try hotswapping it for the BIOS ROM in the 386, but keep in mind, all the address lines may not be hooked up.

AMIBIOS was somethink like 64-128 kilobytes back then, so if, say, the lower 8 address lines are hooked up, you'll get repeating "modulo" falses each time you attempt to cycle the addresses as you dump.

You'll end up with repeating data blocks, the size of which depends on how many ADDR lines are actually connected.


Say only 19 lines are connected, and you "walk" the address count to a full 20 bit cycle. You'll only get data (falsely) represented by the lower 19 bits, twice, but it won't be correct data. Which will make you think the dump has more bad bits than it actually might. Better still, if the corruption is in valid data (on the device), but represented above that 20th bit, you'll never see it if you don't address it properly.


Here's an example from the LBA "137GB" limit. Say you have a 200GB HDD. You'll wrap back around after "137GB." So you want to zero-fill this HDD from 6GB (above your data) to 200GB. Now, once 137GB is reached, you wrap back around to 0bytes, and proceed to wipe the drive from zero bytes up to 63GB! Your data, from 0B to 6GB is gone.

While your utility took "200GB" of "steps," (137GB+63GB), there weren't enough bits to cover all actual physical bits/bytes/LBAs on the drive.

It can happen with everything from that, to even NES/SNES/etc ROM dumps. Those were fun, not all ROMS were over 1MB- you can read them OK since they don't use the higher-order ADDR bits, but dump a 4MB cart w/o that bit, and you get four false images of the same lower 1MB worth of addressable bits.


If you can trace the ADDR lines on the ROM skt on the 386 MB, and all appear connected-connected-connected, give it a shot. You may need to use DEBUG to "peek around."

BTW, what's the part number of the device you're trying to dump?

Edit- Looked at datasheet, it's a 32pin device. You will not be able to plug this into a 28pin skt without a "transposition adapter."

[goontron]

Re: Access Disk On Chip?

Well, this is a dead project now... My nephew just smashed the display!