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authorH. Peter Anvin <hpa@zytor.com>2008-06-07 14:39:01 -0700
committerH. Peter Anvin <hpa@zytor.com>2008-06-07 14:39:01 -0700
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MEMDISK: algorithmic determination of floppy formats
Consider all disks < 4 MB to be floppies, and guess their geometry algorithmically.
Diffstat (limited to 'doc/memdisk.txt')
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diff --git a/doc/memdisk.txt b/doc/memdisk.txt
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+++ b/doc/memdisk.txt
@@ -28,25 +28,44 @@ Note the following:
a) The disk image can be uncompressed or compressed with gzip or zip.
-b) If the disk image is one of the following sizes, it's assumed to be a
- floppy image:
-
- 368,640 bytes - 360K floppy
- 737,280 bytes - 720K floppy
- 1,222,800 bytes - 1200K floppy
- 1,474,560 bytes - 1440K floppy
- 1,720,320 bytes - 1680K floppy (common extended format)
- 1,763,328 bytes - 1722K floppy (common extended format)
- 2,949,120 bytes - 2880K floppy
- 3,932,160 bytes - 3840K floppy (extended format)
-
- For any other size, the image is assumed to be a hard disk image,
- and should typically have an MBR and a partition table. It may
- optionally have a DOSEMU geometry header; in which case the header
- is used to determine the C/H/S geometry of the disk. Otherwise,
- the geometry is determined by examining the partition table, so the
- entire image should be partitioned for proper operation (it may be
- divided between multiple partitions, however.)
+b) If the disk image is less than 4,194,304 bytes (4096K, 4 MB) it is
+ assumed to be a floppy image and MEMDISK will try to guess its
+ geometry based on the size of the file. MEMDISK recognizes all the
+ standard floppy sizes as well as common extended formats:
+
+ 163,840 bytes (160K) c=40 h=1 s=8 5.25" SSSD
+ 184,320 bytes (180K) c=40 h=1 s=9 5.25" SSSD
+ 327,680 bytes (320K) c=40 h=2 s=8 5.25" DSDD
+ 368,640 bytes (360K) c=40 h=2 s=9 5.25" DSDD
+ 655,360 bytes (640K) c=80 h=2 s=8 3.5" DSDD
+ 737,280 bytes (720K) c=80 h=2 s=9 3.5" DSDD
+ 1,222,800 bytes (1200K) c=80 h=2 s=15 5.25" DSHD
+ 1,474,560 bytes (1440K) c=80 h=2 s=18 3.5" DSHD
+ 1,638,400 bytes (1600K) c=80 h=2 s=20 3.5" DSHD (extended)
+ 1,720,320 bytes (1680K) c=80 h=2 s=21 3.5" DSHD (extended)
+ 1,763,328 bytes (1722K) c=82 h=2 s=21 3.5" DSHD (extended)
+ 1,784,832 bytes (1743K) c=83 h=2 s=21 3.5" DSHD (extended)
+ 1,802,240 bytes (1760K) c=80 h=2 s=22 3.5" DSHD (extended)
+ 1,884,160 bytes (1840K) c=80 h=2 s=23 3.5" DSHD (extended)
+ 1,966,080 bytes (1920K) c=80 h=2 s=24 3.5" DSHD (extended)
+ 2,949,120 bytes (2880K) c=80 h=2 s=36 3.5" DSED
+ 3,194,880 bytes (3120K) c=80 h=2 s=39 3.5" DSED (extended)
+ 3,276,800 bytes (3200K) c=80 h=2 s=40 3.5" DSED (extended)
+ 3,604,480 bytes (3520K) c=80 h=2 s=44 3.5" DSED (extended)
+ 3,932,160 bytes (3840K) c=80 h=2 s=48 3.5" DSED (extended)
+
+ A small perl script is included in the MEMDISK directory which can
+ determine the geometry that MEMDISK would select for other sizes;
+ in general MEMDISK will correctly detect most physical extended
+ formats used, with 80 cylinders or slightly more.
+
+ If the image is 4 MB or larger, it is assumed to be a hard disk
+ image, and should typically have an MBR and a partition table. It
+ may optionally have a DOSEMU geometry header; in which case the
+ header is used to determine the C/H/S geometry of the disk.
+ Otherwise, the geometry is determined by examining the partition
+ table, so the entire image should be partitioned for proper
+ operation (it may be divided between multiple partitions, however.)
You can also specify the geometry manually with the following command
line options: