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Groups > alt.lang.asm > #6768

Re: exFAT12

From "Mike Gonta" <mikegonta@gmail.com>
Newsgroups alt.lang.asm, alt.os.assembly, alt.os.development
Subject Re: exFAT12
Date 2016-12-06 18:18 -0500
Organization Aioe.org NNTP Server
Message-ID <o27gv8$1v9a$1@gioia.aioe.org> (permalink)
References <o1ns48$1srh$1@gioia.aioe.org>

Cross-posted to 3 groups.

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"Mike Gonta" wrote:
>A gentle introduction to the exFAT file system in FASM.

exFAT boot sector boot loader and pre-processor FASM assembly
language code to format a 1.44MB image for emulation or transfer
to USB boot and run.

The single sector boot sector boot loader contains a subset of a
complete read-only exFAT file system driver.
In order to fit completely in the restricted size of a boot sector
some restrictions apply.

* The loaded file name must be no more than 12 ascii (7 bit)
  characters in the 8 dot 3 style (the dot is optional).
* One sector per cluster.
* Maximum file size of 127 (512 byte supported) sectors loaded at
  0x1000:0000.
* Minimal single character numerical error code display.

Statistics for bit counters.

* 120 bytes for the mandatory BPB (58 bytes more than FAT12 and
  30 bytes more than FAT32).
* 16 bytes for a self-referencing MBR partition table entry. This
  allows the transferred image to USB to be mounted by Windows which
  will not mount an exFAT formatted device with a BPB volume_length
  less than the physical capacity unless it's partitioned.
* 12 bytes for loaded file name.
* 2 bytes for the manditory 0xAA55 signature.
* 9 unused bytes

That leaves a whopping 353 bytes for code and data.
~430 LOC of commented FASM assembly language.

http://mikegonta.com/exFAT12
https://board.flatassembler.net/topic.php?p=192148#192148
http://forum.osdev.org/viewtopic.php?f=2&t=31044
https://redd.it/5gw4lv


Mike Gonta
look and see - many look but few see

 http://mikegonta.com

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Thread

exFAT12 "Mike Gonta" <mikegonta@gmail.com> - 2016-11-30 19:50 -0500
  Re: exFAT12 Robert Wessel <robertwessel2@yahoo.com> - 2016-12-01 02:29 -0600
    Re: exFAT12 "Mike Gonta" <mikegonta@gmail.com> - 2016-12-01 06:10 -0500
      Re: exFAT12 Robert Wessel <robertwessel2@yahoo.com> - 2016-12-01 06:16 -0600
        Re: exFAT12 "Mike Gonta" <mikegonta@gmail.com> - 2016-12-01 08:57 -0500
          Re: exFAT12 Rod Pemberton <NeedNotReplyHere@xrsevnneqk.cem> - 2016-12-01 16:15 -0500
            Re: exFAT12 "Mike Gonta" <mikegonta@gmail.com> - 2016-12-01 18:14 -0500
  Re: exFAT12 JJ <jj4public@vfemail.net> - 2016-12-01 17:23 +0700
    Re: exFAT12 "Mike Gonta" <mikegonta@gmail.com> - 2016-12-01 06:28 -0500
  Re: exFAT12 "Mike Gonta" <mikegonta@gmail.com> - 2016-12-06 18:18 -0500
    Re: exFAT12 "Mike Gonta" <mikegonta@gmail.com> - 2016-12-07 09:57 -0500

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