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Groups > alt.os.development > #8216

Re: BIOS limits on CD boot ?

From "wolfgang kern" <nowhere@never.at>
Newsgroups alt.os.development
Subject Re: BIOS limits on CD boot ?
Date 2015-06-20 09:18 +0200
Organization KESYS-development
Message-ID <mm3450$jrr$3@speranza.aioe.org> (permalink)
References <mm0vas$t3l$1@speranza.aioe.org> <op.x0hz3wplyfako5@localhost>

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Rod Pemberton wrote:
 
>> Let's assume a bootable OS on an ISO 9660 conform CD/DVD.
> ...
>> How many bytes can the BIOS load from such media ?
 
> Are you overwriting the same block repeatedly?  If so, I'd assume
> an infinite number.  If not, I'd assume you could load until you
> either ran into the BIOS, video ROMs, or installable ROMs at 640K,
> or you exceeded available memory on machine with only 512K of memory.

Which BIOS function would you suggest to read from CD ?
 
>> As I figured some time ago, INT13_42 can't load above 1.MB,
>> but if the BIOS can load 500K to 0x08000...
> 500K + 32K = 512K + 20K
> I.e., below 640K, but above 512K which only matters for old machines.

with 500k I meant 524288 bytes anyway, 
so my load range would be from 08000...87fff or 07c00...87bfff if 
the BIOS can load a boot-image that large.
 
>> that would be enough for me yet and it could save me from
>> temporary installing my CD-reader for the boot.
 
> That's worth a few bad CDs, yes? ...

It's not the value of the CDs, just the annoyance if it wont work.
 
>> So I ask here before I burn several CDs to check if this work.
 
> Who uses CDs anymore?  Haven't you heard, everyone moved to the
> "cloud" four years ago, according to Apple computer.  LOL. ;-)
 
this guys smoke too much of the carpet and may see only clouds yet. 
My idea is to use bootable CDs for demos and tutorials.
And I wont send it to cloud-watchers of course. 
__
wolfgang

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Thread

BIOS limits on CD boot ? "wolfgang kern" <nowhere@never.at> - 2015-06-19 13:44 +0200
  Re: BIOS limits on CD boot ? "James Harris" <james.harris.1@gmail.com> - 2015-06-19 14:15 +0100
    Re: BIOS limits on CD boot ? "wolfgang kern" <nowhere@never.at> - 2015-06-19 19:07 +0200
      Re: BIOS limits on CD boot ? Melzzzzz <mel@zzzzz.com> - 2015-06-19 19:22 +0200
        Re: BIOS limits on CD boot ? "wolfgang kern" <nowhere@never.at> - 2015-06-20 08:50 +0200
      Re: BIOS limits on CD boot ? "James Harris" <james.harris.1@gmail.com> - 2015-06-20 09:07 +0100
        Re: BIOS limits on CD boot ? "James Harris" <james.harris.1@gmail.com> - 2015-06-20 15:43 +0100
          Re: BIOS limits on CD boot ? "wolfgang kern" <nowhere@never.at> - 2015-06-21 06:10 +0200
            Re: BIOS limits on CD boot ? "James Harris" <james.harris.1@gmail.com> - 2015-06-21 18:13 +0100
              Re: BIOS limits on CD boot ? "wolfgang kern" <nowhere@never.at> - 2015-06-22 09:55 +0200
                Re: BIOS limits on CD boot ? "James Harris" <james.harris.1@gmail.com> - 2015-06-22 12:04 +0100
                Re: BIOS limits on CD boot ? "wolfgang kern" <nowhere@never.at> - 2015-06-30 20:03 +0200
                Re: BIOS limits on CD boot ? "James Harris" <james.harris.1@gmail.com> - 2015-07-01 11:19 +0100
  Re: BIOS limits on CD boot ? "Benjamin David Lunt" <zfysz@fysnet.net> - 2015-06-19 10:56 -0700
    Re: BIOS limits on CD boot ? "wolfgang kern" <nowhere@never.at> - 2015-06-20 08:55 +0200
  Re: BIOS limits on CD boot ? "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-06-19 18:15 -0400
    Re: BIOS limits on CD boot ? "wolfgang kern" <nowhere@never.at> - 2015-06-20 09:18 +0200
      Re: BIOS limits on CD boot ? "Benjamin David Lunt" <zfysz@fysnet.net> - 2015-06-20 07:43 -0700
  Re: BIOS limits on CD boot ? "wolfgang kern" <nowhere@never.at> - 2015-06-21 16:04 +0200
    Re: BIOS limits on CD boot ? "James Harris" <james.harris.1@gmail.com> - 2015-06-22 12:13 +0100

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