Re: [NILO-discuss] Zen and the art of running in real mode

[H. P. A. <hp...@zy...>]

Michael Brown wrote:
>>
>>Right.  With appropriate descriptors set up they could work in 16-bit 
>>protected mode, though, for supporting the PM entry point.
> 
> They could, but that wouldn't help the code when it's called via the RM 
> entry point.
> 

Supporting V86 mode entry via the RM entry point is probably futile.

> Also, the cards we're talking about are quite likely to need more than 
> 64kB of data buffers, in which case we can't fit it into the strict UNDI 
> model (64kB code + 64kB data+bss+stack, all in base memory) anyway.  We 
> have to accept that the PXE specification is actually incompatible with 
> some network cards, and plan to carefully violate the spec.

Indeed, although the !PXE structure clearly is designed to accommodate 
additional descriptors.

(Note: for a lot of cards which *can* have > 64K data buffers, generally 
don't *have* to.  For example, a device with a 1024-entry descriptor 
ring can be filled with only a few entries, on the assumption that 
performance is secondary in our application.)

	-hpa