OSDev.org

Hi all

I have DMA and floppy drivers in my OS which works in Bochs, QEMU, Parallels, MS VM, plus on a number of desktop computers.

However on a couple of laptops, most significantly an old 486SX Toshiba T2100CT, the FDC fails with a TO error (DMA overrun on read accesses).

The DMA controller is initialised from scratch, with no preconception about how the BIOS left it prior to my OS taking control. The specs on this laptop says FDC uses DMA#2 and IRQ#6 - pretty standard.

I guess what I am asking, is if there is a central repositary somewhere containing 'gotchas' for variations of computer hardware implementations.

The same for the A20 enable control - too many non-standard variations!

Thanks in advance,

Gary

I'm not aware of any such list, typically the hardware interface is standardized..

There is a local article on the floppy controller here, see this.. and perhaps this.

It could possibly be a timing/delay issue, or perhaps a faulty drive.

As for that laptop, I have here a Toshiba T1910 you can use to test with.. it has 486SX as well, haven't had any issues with the floppy drive that weren't BIOS induced (..has to be reset before it'll read anything, hence most loaders fail without modification).

Would that help?

Problem solved - some tim back now!

The DMA controller was not as versatile as I'd like - but I guess many others before myself have found this out...

I was trying to abstract the hardware too much, to handle other DMA controllers and platforms... Doh!