Strange PMAC IDE performance problem

[Benjamin Herrenschmidt]

On Wed, Jan 6, 1999, Paul Mackerras <paulus at cs.anu.edu.au> wrote:

>I found a register at 0xf3020200 on my powermac G3 which affects the
>speed of disk transfers.  This is at offset 0x200 from the base
>address of the IDE interface and it is a 32-bit little-endian
>register.  After booting Linux, it has 0x2f8526 in it, but under MacOS
>it has 0x211025.  Putting 0x211025 in (with xmon) increased the speed
>reported by hdparm -tT /dev/hda from 1.89MB/s to 9.7MB/s !  The disk
>is a WDC 24300ACL (as reported by hdparm -i /dev/hda).  The other
>hdparm settings were -d1 -u1 -m16.

I confirm, I have the same values in this register here on PowerMac
G3/300 desktop (without any IDE device plugged in) and in PowerBook G3
Series. I didn't check the iMac yet but it looks like an heathrow thing. 

if you don't find a similar thing on O'Hare, I suggest checking the
"compatible" property of mac-io against heathrow before putting anything here.

-- 
           E-Mail: <mailto:bh40 at calva.net>
BenH.      Web   : <http://calvaweb.calvacom.fr/bh40/>





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