[rescue] Sun Ultra 5 video

Meelis Roos mroos at linux.ee
Sat Dec 20 18:07:53 CST 2003

> > (1) Does the U10's IDE controller have a limitation on the size and/or
> > speed of drives it can talk to?

I tried to determine whether it has the 128GiB/137GB limit or not. LBA48
support is needed to use more than 128GiB. Mostly, the driver and the
disk need to support LBA48 but some IDE controllers have quirks that
prevent LBA48 from working. Or raher, prevent LBA48 from working in DMA
mode - so far, no controllers have been found where LBA48 would not work
in PIO mode. In DMA mode, some register needs to be read twice and this
confuses some IDE controller chips.

Well, since the cmd64x driver in Linux (for 643, 646, 648 and 649 chips)
does not set no_lba48 flag, I suppose the Linux driver supports the
>137GB disks too. Haven't treid though. No idea about Solaris.

> I don't know and I don't care. The IDE chip in the U5 / U10 is the CMD
> 646. The Linux Kernel has a special option only to work around bugs in
> that chip. I read on NetBSD/port-alpha that this chip has a somewhat
> broken DMA, thus giving abyssal performance. => Don't use it.

The workaround was for CMD640, a completely different chip with a
special driver.

CMD646 works fine, it's also present in some Alphas and works fine there
too. It's nothing special, a normal pre-UDMA IDE controller, normal DMA

Meelis Roos (mroos at linux.ee)

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