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Subject:	RE: SCSI drives (was: Fun with USB)
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Date:	Tue, 28 Jun 2005 19:24:47 +1000
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Thread-topic:	Fun with USB
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From:	"da Silva, Joe" <Joe DOT daSilva AT ampymetering DOT com DOT au>
To:	<opendos AT delorie DOT com>
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Reply-To:	opendos AT delorie DOT com

Hey, proponents of SCSI always tell me there is
no intrinsic limitation to the access capacity
for SCSI drives!  <G>

Getting serious for a moment, from memory, the
8G limit arose from the number of bits allocated
for CHS addressing in the traditional Int 13h API.

So, I guess if you are encountering this limit, you
must have SCSI drivers or BIOS that are providing a
traditional Int 13h API to DOS. Which would mean
two things are required to break this limit.

Firstly, you need SCSI drivers or BIOS that provide
an Extended Int 13h API.

Secondly, you need a version of DOS that knows about
the Extended Int 13h API. AFAIK (not 100% sure for
all of them), these are :

- DR-DOS 7.02+ with the FAT32 driver ?
- Enhanced Open-DOS 7.01 (http://www.drdosprojects.de/)
- DR-DOS 8.00
- MS-DOS 7.10 & ROM-DOS 7.10
- MS-DOS 8.00 (I think that's the version under ME)
- FreeDOS X.XX (sorry, no idea about the numbering)
- RX-DOS X.XX (sorry, no idea about the numbering)
- Others ?

I'm not sure if any DOS version has direct support for
SCSI/ASPI, in which case support for the Extended Int
13h API may not be necessary.

Note that all my PC drives are IDE, so if any of the
above is incorrect, hopefully someone who has more
hands-on experience with SCSI drives can set things
straight ... Certainly, I seem to remember the SCSI
proponents claiming they had no intrinsic limitations
in access capacity, even before the Extended Int 13h API
came into existence, but perhaps that wasn't with DOS?


Joe.


> -----Original Message-----
> From: Gary Welles [mailto:gary AT wellesway DOT com]
> Sent: Tuesday, 28 June 2005 3:43 PM
> To: OpenDos
> Subject: Re: Fun with USB
> 
> 
> Joe da Silva writes:
> 
> > Well, I see no reason why this wouldn't work for
> > any size USB drive. It treats USB drives like SCSI,
> > so I don't think the 512M/8G boundaries found with
> > various IDE & BIOS combinations apply.
> 
> I have some 18Gb SCSI drives and so far have been unable to
> use more than 8Gb of them.
> 
> -- Gary Welles
> 
> 
> 

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