X-Authentication-Warning:	delorie.com: mailnull set sender to djgpp-bounces using -f
Date:	Tue, 22 Jan 2002 10:36:28 +0200
From:	"Eli Zaretskii" <eliz AT is DOT elta DOT co DOT il>
Sender:	halo1 AT zahav DOT net DOT il
To:	"Tim Nicholson" <djgpp AT gizzy DOT co DOT uk>
Message-Id:	<8011-Tue22Jan2002103628+0200-eliz@is.elta.co.il>
X-Mailer:	emacs 21.2.50 (via feedmail 8 I) and Blat ver 1.8.9
CC:	djgpp AT delorie DOT com
In-reply-to:	<1011635483.28296.0.nnrp-08.c1ed6b28@news.demon.co.uk>
	(djgpp AT gizzy DOT co DOT uk)
Subject:	Re: Protected Mode disk access
References:	<1011635483 DOT 28296 DOT 0 DOT nnrp-08 DOT c1ed6b28 AT news DOT demon DOT co DOT uk>
Reply-To:	djgpp AT delorie DOT com
Errors-To:	nobody AT delorie DOT com
X-Mailing-List:	djgpp AT delorie DOT com
X-Unsubscribes-To:	listserv AT delorie DOT com

> From: "Tim Nicholson" <djgpp AT gizzy DOT co DOT uk>
> Newsgroups: comp.os.msdos.djgpp
> Date: Mon, 21 Jan 2002 17:45:50 -0000
> 
> Am I correct in thinking the DJGPP switches from protected mode to real mode
> to access the HDD and transfers data in 64K blocks (variable) via the DPMI
> to and from DOS?

True, except that the default buffer size is 16KB, not 64KB.

> The reason for asking is that disk I/O seems much faster under Windows 98/ME
> etc. and I am guessing this is partly because the whole thing is happening
> in protected mode.

If you are comparing DOS and Windows, and see a significantly faster
I/O on Windows, I suggest to install a large SmartDRV cache on the
DOS machine, set it up to delayed-write operation, and try again.
Chances are, you will see disk I/O that's as fast as on Windows.
(Details can be found in section 3.9 of the DJGPP FAQ list.)

If you already have SmartDRV installed, please post the command line
used to install it in AUTOEXEC.BAT.

> Does DOS (the one shipped with Win98) utilise the full capabilities of the
> drive (i.e.. UDMA100 etc)?

Not DOS, BIOS.  DOS doesn't talk to the disk directly.

- Raw text -