Re: TP360CE: NetBSD-1.0 and RAM

[Don Whiteside <dwhite@shadow.net>]

On Mon, 6 Feb 1995, Arne Helme wrote:

> Could someone please help me out with this one; Since IBM seems to
> have problems with the delivery of RAM cards to the thinkpads, I have
> been offered a replacement card from Kingston (either 8 MB or 16 MB).
> Is there anyone out there who has some experience with these cards?
> It seems that I'll be able to buy a 16 MB Kingston card for almost the
> same price as a 8 MB IBM card.  This leads to my next question; are
> there any performance problems with running NetBSD on a thinkpad with
> more than 16 MB of RAM?  I am not that familiar with the internals of
> these machines, but if I remember correctly, the performance of NetBSD
> degrades when the 16 MB RAM boundary is crossed.

  I believe you're extrapolating outward from the fact that bus mastering 
SCSI cards perform badly above 16M. Any bus mastering device in an ISA 
machine (since the bus only has 16 bits for addressing) must use bounce 
buffering.  This makes it not as efficient as accessing the lower 16M of 
memory.
  GENERAL performance should not be effected. And since the TP uses IDE, 
which is not a DMA device, this is not applicable.

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Donald Alan Whiteside			School of Computer Science
       Official Usenet Dork for the week of Jan 9-13, 1995
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