Re: Max. HD size Ultra5

From: Casper H.S. Dik (Casper.Dik_at_Sun.COM)
Date: 07/18/04 

Date: 18 Jul 2004 14:13:41 GMT

"Benjamin Gawert" <bgawert@gmx.de> writes:

>DMA ("Direct Memory Access") simply means that the IDE controller can push
>the data direct into the computers' memory instead of having to use the cpu
>for that (Polling, used with the old PIO modes). This indeed is dependent
>from the firmware _and_ from the controller but has absolutely _nothing_ to
>do with the disk size. You can use 300GB disk in PIO mode if You want, it
>will be slow like hell and cause a lot of CPU load but it will work fine.

It's not when you take into account how broken hardware can be;
the specific IDE controller chips in the U10/U5 cannot support 48bits
LBA in DMA mode, only 28 bits LBA (they can do 48 bits LBA but only
when using PIO)

The IDE *driver* on SPARC only does 28 bit LBA; it doesn't know
about 48 bit LBA.

>No, there aren't. As I said before the 128GB disk size limit is only a
>OpenFirmware limitation (28Bit adressing scheme). As soon as the OS is
>loaded a driver takes control over the IDE controller, and from this time
>for a secondary drive You're limited only to the disk size addressable by
>that driver. Sadly, the Solaris drivers take the disk size reports from OFw
>when loeading, but long ago I somehwere found a description how to make the
>driver requesting the disk size from the disk rather from OFw. I just
>followed the description and it worked. The disk now contains two 80Gb /home
>and /home2 directories and a 40GB ftp directory.

Well, the bug report about only support 28 bit LBA is still open
and mentions hardware limitations of the SPARC IDE controller chips.

So I'm very curious why it would work for you.

Casper

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