Re: Disabling PIO / LBA48 on large drives , Blade 150

> Date: Mon, 19 Sep 2011 10:47:30 -0700 (PDT)
> From: Bill Johnstone <[email protected]>
> 
> Hello,
> 
> I'm trying to put a Blade 150 to use.  I installed two 160 GB UDMA
> drives to replace the 40 GB Seagate drive the machine shipped with.
> Unfortunately, the Blade 150 uses the ALI (Acer) M5229 series ATA controller
> chip, which (at least for the revs on these Suns) can't do DMA simultaneously
> with LBA48 addressing.
> 
> In src/sys/dev/pci/pciide.c the acer_dma_init function
> seems to handle this by checking to see if the LBA48 flag is turned on, and if
> so, returning EINVAL , resulting in PIO transfers only for the disk.  I would
> much rather use DMA with some loss of capacity than use PIO, particularly with
> the disks I have (it wouldn't be much capacity lost).

In wd(4), we only actually use the LBA48 flag for requests that
actually need it (see __wdstart()).  So reads and writes from/to the
start of the disk will use the LBA flag and use DMA just fine.

So just make sure you keep the end of your disks empty and things
should just work fine.