To: Martin AT snsystems DOT co DOT uk
Cc: djgpp AT sun DOT soe DOT clarkson DOT edu
Subject: Re: Disk I/O rates with DJGPP 
Date: Mon, 07 Nov 94 17:06:13 +0200
From: "Eli Zaretskii" <eliz AT is DOT elta DOT co DOT il>

> My real question here is why does go32 have a 30% time overhead on a
> disk read when X32 only has a 5% overhead (reading in 4k byte block
> sizes in both cases) ?  Is the routine to copy data in/out of the
> real mode memory buffer slow or (more likely) is the transition
> to/from virtual 8086 mode slow ?

Probably because in X32, even if you specify a 4k block, the extender
still reads larger chunks and only passes data to you in 4k bytes.
I don't really know the fine details of mode switch, but it could also
be a culprit, although I would doubt if any reasonable mode switch code
would take so long as to explain the above difference.