On 30-12-07 18:06, Ingo Molnar wrote:

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> * Rene Herman <rene.herman@keyaccess.nl> wrote:

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>> Real ISA systems will also generally respond faster to it than the 
>> unused port (this thing actually has an ISA bus but not VGA on it 
>> ofcourse) which means that "a perfect delay register" it is not. But 
>> yes, I have an actual Am386DX-40 with ISA VGA up and running which 
>> also doesn't care either way, about the ones in misc_32.c or anywhere 
>> else for that matter.
> 
> yeah - and that's typical of most _p() use: most of them are totally 
> bogus, but the global existence of the delay was used as a "it _might_ 
> break system" boogey-man against replacing it.

No delaying at all does break a few systems.

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> so _IF_ we do any delay in x86 platform drivers, we at most do a delay 
> on the order of the round-trip latency to the same piece of hardware we 
> are handling.

Given that part of the problem is 2 MHz devices on a 8 MHz bus, you can't do 
this generally.

Rene.
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