Re: On I/O and memory address space

[John R Pierce <pierce@hogranch.com>]

At 04:30 PM 2/10/97 -0800, Brian Sassone wrote:
>
>> 2. If you want to do burst reads/or writes to your device from a host,
>> then the memory space should be marked prefetchable.
>
>Is this statement completely true?  It was my understanding that a target
>would get burst writes even if the space was marked non-prefetchable since
>most bridges will still practice write combining.

I agree. In fact, virtually no VGA cards are marked prefetchable, yet write
bursts are a fact of life.  Being non-prefetchable does imply that partial
writes won't be combined (byte write followed by word write for instance),
but host writes to incrementing addresses certainly get merged by the common
triton bus bridges.
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