Subject: Re: pciide performance on alpha
To: Matt Thomas <>
From: Manuel Bouyer <>
List: port-alpha
Date: 08/24/1999 16:02:03
On Wed, Aug 18, 1999 at 06:31:37PM -0700, Matt Thomas wrote:
> Well, I finally figured what PCIIDE DMA wasn't working.  The V5.1 SRM on
> my 164SX sets the bus_master_dma basereg to an address over 0xffff.  The
> problem is that the Cypress only looks at the bottom 16 bits.  It brokenly
> reports the upper 16bits as what was written instead of 0.  But masking
> off the upper 16 bits, I can get PCIIDE DMA to work.
> But I only get 3.4MB/s (but at < 1% cpu utilization).  However using a 
> IDE->SCSI converter connected to a ncr53c810a with the identical drive, 
> I can get > 6MB/s.  Off a 875 I get > 7MB/s (since the 875 still negotiates
> at 10MB/s).  Digital UNIX gets > 8MB/s off the same drive (using IDE) 
> because it modifies the timing of the drives.

Do you know if the latency timer is properly set ?
If not, could you try the patch that has been posted to the list which sets it
to a more sensible value ?

If this doesn't help I'll try to have a look at the cypress docs again,
maybe there's a problem with the chip's timings initialisation,
after all ... :)
Does someone else with a cypress get decent performances with DMA drives ?

Manuel Bouyer, LIP6, Universite Paris VI.