Re: [Linux-fbdev-devel] Re: fbcon slowness [was NTP on 2.4.2?]

[Ivan K. <in...@ju...>]

On Thu, Apr 05, 2001 at 12:20:22PM -0600, Eric W. Biederman wrote:
> The point is on the Alpha all ram is always cached, and i/o space is
> completely uncached.  You cannot do write-combing for video card
> memory.

Incorrect. Alphas have write buffers - 6x32 bytes on ev5 and
4x64 on ev6, IIRC. So alphas do write up to 32 or 64 bytes
in a single pci transaction.

>  Memory barriers are a separate issue.  On the alpha the
> natural way to implement it would be in the page table fill code.
> Memory barriers are o.k. but the really don't help the case when what
> you want to do is read the latest value out of a pci register.  

You don't need memory barrier for that. "Write memory barriers" are
used to ensure correct write order, and "memory barriers" are used
to ensure that all pending reads/writes will complete before next read
or write.

Ivan.