From:	ps AT ocisgi7 DOT unizh DOT ch (Serge Pachkovsky)
Subject:	Re: _bios_disk() inefficiency
Newsgroups:	comp.os.msdos.djgpp
References:	<Pine DOT SUN DOT 3 DOT 91 DOT 980308133407 DOT 22686H-100000 AT is>
NNTP-Posting-Host:	ocisgi7.unizh.ch
Message-ID:	<35029541.0@rzunews1.unizh.ch>
Date:	8 Mar 98 12:55:29 GMT
Lines:	26
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Eli Zaretskii (eliz AT is DOT elta DOT co DOT il) wrote:

: advice.  Theoretically, you could make a DJGPP version 1000 times
: slower if you, for example, called the BIOS for every byte you needed
: to read.  Calling BIOS requires a mode switch which is slow, so you
: should make as few calls as you can.  In particular, reading more of
: the disk at a time and then working on data in memory should speed
: your program a lot.  In DJGPP, you could even read an entire diskette
: into memory in one swell whoop.

No Eli, you can't - most floppy disk BIOSes do not support reading more
that one cylinder's worth of data in a single call. Even if your particular
BIOS can do it (something you shouldn't rely upon), 8-bit DMA channel
used by floppy drives won't allow you to transfer more than 64Kb worth
of data without re-initialization. Even if your BIOS can miraculously
circumvent this limitation, you won't have enough low memory to buffer
the data coming from a single HD floppy anyway. Don't I love PCs...

Regards,

/Serge.P

--

Russian guy from the Zurich university...

- Raw text -