5121 cache handling.

[Kenneth Johansson]

On Mon, 2009-08-10 at 15:26 -0500, Scott Wood wrote:
> Kenneth Johansson wrote:
> >>> should not the framebuffer be marked as cache write through. that is the
> >>> W bit should be set in the tlb mapping. Why is this not done ? is that
> >>> feature also not working on 5121 ??
> >> It probably would have been too slow.
> > 
> > how much slower would write through be ? I thought it was not that big
> > of a difference from copy back.
> 
> It's a big difference if you're writing out an entire cache line of data 
> anyway, but because of write-through it goes out one word at a time 
> without bursting.
> 
> -Scott
> 
Yes the memory system would obviously get a higher load but do the CPU
actually see that? do it stall on the write ?