Name¶
mkdisk - Make a blank emulated floppy or hard disk for xtrs, or add/remove an
emulated write protect tab
Syntax¶
mkdisk -1 filename
mkdisk [-3] filename
mkdisk -k [-s sides] [-d density] [-8] [-i] filename
mkdisk -h [-c cyl] [-s sec] [-g gran] filename
mkdisk {-p|-u} {-1|-3|-k|-h} filename
Description¶
The mkdisk program is part of the
xtrs(1) package. It has two distinct
functions: (1) It can make a blank (unformatted) emulated floppy or hard drive
in a file. (2) With the -p or -u flag, it can turn the write protect flag on
or off for an existing emulated floppy or hard drive file. See the xtrs man
page for background information.
The conventional file extensions are .dsk for emulated floppies and .hdv for
emulated hard drives, but
mkdisk does not enforce this convention; you
can use any filename. Other extensions sometimes used for emulated floppies
are .jv1, .jv3, .8in, and .dmk.
Making Emulated Floppies¶
With the -1 flag,
mkdisk makes an unformatted emulated floppy of type
JV1. No additional flags are accepted.
With the -3 flag (which is the default and should normally be used),
mkdisk makes an unformatted emulated floppy of type JV3. No additional
flags are accepted.
With the -k flag,
mkdisk makes an unformatted emulated floppy of type
DMK. With -k, the optional flags -s, -d, -8, and -i can be used to give the
emulated floppy special properties. Specifying -s1 limits the floppy to one
side; with -s2 (the default), the floppy can be formatted as either one- or
two-sided. Specifying -d1 limits the floppy to single density; with -d2 (the
default), the floppy can be formatted in either single or double density.
Specifying -8 allows the floppy to be formatted in an emulated 8" drive;
by default it will work properly only in an emulated 5" drive. Setting
-s1 or -d1 saves space after the floppy is formatted; setting -8 consumes
additional space. Specifying -i activates a peculiar feature in some TRS-80
emulators that causes each formatted sector to appear to be both single and
double density.
Making Emulated Hard Drives¶
With the -h flag,
mkdisk makes an unformatted emulated hard drive with
cyl cylinders,
sec sectors, and
gran granules (LDOS
allocation units) per cylinder. The hard drive will have cylinder
dir
marked for use as its directory.
You will usually want to use the default values for all these parameters. The
default is 202 cylinders, 256 sectors per cylinder (that is, 8 heads and 32
sectors per track), and 8 granules per cylinder. This is the largest hard
drive that can be used by all LDOS/LS-DOS operating systems without
partitioning the drive or patching the FORMAT command. The details on what
nondefault values are possible vary, depending on which of xtrs's two hard
drive emulations you are using and which other emulators you want to be
compatible with, and it is probably best not to delve into these complexities,
but read on if you really want to.
For
cyl, the number of cylinders on the drive, the default value is 202,
the minimum is 3, and the maximum that can be represented in the HDV file's
header is 256. You can use 203 cylinders with LDOS and LS-DOS if you format
the drive with Model 4 LS-DOS; a minor bug in Model I/III FORMAT/CMD prevents
more than 202 cylinders from being formatted, but the system can use 203
thereafter. 203 cylinders is the absolute maximum for LDOS/LS-DOS drivers that
do not support partitioning, including the emulator-specific drivers supplied
with xtrs (XTRSHARD/DCT), with Matthew Reed's emulator (HARD/CMD), and with
David Keil's emulator (EHARD/DCT).
In xtrs 4.1 and later, and in David Keil's emulator version 6.0 and later, a
true emulation of Radio Shack's WD1010-based hard disk controller is also
available, which works with the native drivers for the original hardware, such
as RSHARDx/DCT and the hard disk drivers for NEWDOS and CP/M. In xtrs, the
WD1010 emulation ignores the maximum number of cylinders specified in the HDV
file's header and allows the driver to format up to 65536 cylinders. This may
be useful if your drivers support partitioning (but why would anyone want to
partition an emulated hard drive instead of just making two smaller ones?), or
if your operating system supports more than 203 cylinders per partition. Note
that although RSHARDx/DCT allows up to 406 cylinders per partition, if you use
more than 203, the maximum number of sectors per cylinder is limited to 128,
so you gain nothing; the maximum size of a partition is still the same.
For
sec, the number of sectors per cylinder, the default value is 256,
the maximum is 256, and the minimum is 4. There are some restrictions on the
values that will work. For the greatest portability, choose a value that is
divisible by 32. With xtrs's XTRSHARD/DCT and David Keil's EHARD/DCT, any
value is allowed that can be evenly divided into granules; see the next
paragraph. With Matthew Reed's HARD/CMD, if
sec is greater than 32, it
must be divisible by 32. With the emulation of a real WD1010 in newer versions
of xtrs (and probably David Keil's emulator too),
sec must always be
divisible by 32, because we always emulate a drive with 32 sectors per track
and from 1 to 8 heads (tracks per cylinder). The RSHARDx/DCT driver assumes
that there are always 32 sectors per track.
For
gran, the default value is 8, the maximum is 8, and the minimum is 1.
In addition, it is necessary that
sec be evenly divisible by
gran, and that
sec/gran be less than or equal to 32. This value
is used only with the emulator-specific drivers listed above; it is ignored
when xtrs is using native hardware drivers such as RSHARDx/DCT.
The maximum size of a hard drive image is controlled by
cyl and
sec: it can be at most
cyl*sec 256-byte sectors. The image file
starts out small and grows as you write to more cylinders. The allocation
efficiency is controlled by the granule size: LDOS allocates file space in
granules. Therefore (1)
gran should always be set as large as possible
and (2) reducing
sec, thereby making the granules smaller, reduces
wasted space due to fragmentation but limits the maximum size of the drive.
Seeing that the maximum unpartitioned drive size is less than 13 MB and that the
maximum granule size is only 8 KB, wasted space should not be much of a
concern for most
xtrs users. Therefore the default parameters have been
chosen to give you the largest drive possible without partitioning.
Write Protection¶
With the -p flag,
mkdisk turns on write protection for an existing
emulated floppy or hard drive. It turns off all Unix write permission bits on
the file, and (except for JV1 floppies) also sets a write-protected flag
inside the file.
With the -u flag,
mkdisk turns off write protection for an existing
emulated floppy or hard drive. It turns on Unix write permissions to the file,
masked by your current umask and the file's current read permissions. It also
clears a write-protected flag inside the file (except on JV1 floppies, which
don't have such a flag).
mkdisk currently does not have code to auto-recognize file formats, so
the -p or -u flag must be accompanied by either -1 (JV1), -3 (JV3), -k (DMK),
or -h (hard disk) to identify the file format. There is also no checking for
the correct file format, so if you give the wrong flag, the wrong byte inside
your file will be changed.
Technical data¶
The JV1 format is just an array of 256-byte sectors, in the order (track 0
sector 0, track 0 sector 1, ... track 0 sector 9, track 1 sector 0, ...). It
can represent only single-sided, single-density floppies. The directory is
assumed to be track 17.
The original JV3 format is documented in the printed manual for Jeff Vavasour's
commercial Model III/4 emulator. The xtrs implementation includes some
extensions.
Full documentation for both JV1 and JV3 can be found at
http://www.tim-mann.org/trs80/dskspec.html. A copy of this html file is also
included in the
xtrs distribution.
The DMK format is documented in a file on David Keil's web site,
http://discover-net.net/~dmkeil/trsdoc.htm#Technical-disks; this file is also
included with his emulator. Some updates to the 4.00 version of the document:
(1) If neither the single density nor ignore density option is set and single
density data is recorded, each single density byte is written twice (i.e., the
four bytes 12345678 would be written as 1212343456567878). This ensures that
when single and double density sectors are mixed, each type occupies the
correct relative amount of space in the track. This update will be effective
in version 4.3 of David's emulator; it is incompatible with previous versions.
(2) Bit 15 of an IDAM offset is 1 if the sector is double-density, 0 if single
density. Bit 14 is reserved; it currently must be 0. The actual offset is in
bits 13-0. These offsets are relative to the start of the track header, they
must be in ascending order (I hope!!), and an offset of 0 or 0xffff terminates
the list.
An HDV (hard disk) image has the following format. This information is based on
email from Matthew Reed. There is an initial 256-byte header block, followed
by an array of sectors. The geometry of the drive is defined in the header
block, which looks like this (from mkdisk.c):
typedef unsigned char Uchar;
typedef struct {
Uchar id1; /* 0: Identifier #1: 56H */
Uchar id2; /* 1: Identifier #2: CBH */
Uchar ver; /* 2: Version of format: 10H = version 1.0 */
Uchar cksum; /* 3: Simple checksum:
To calculate, add together bytes 0 to 31 of header
(excepting byte 3), then XOR result with 4CH */
Uchar blks; /* 4: Number of 256 byte blocks in header: should be 1 */
Uchar mb4; /* 5: Not used, currently set to 4 */
Uchar media; /* 6: Media type: 0 for hard disk */
Uchar flag1; /* 7: Flags #1:
bit 7: Write protected: 0 for no, 1 for yes
[warning: xtrs currently ignores this flag]
bit 6: Must be 0
bit 5 - 0: reserved */
Uchar flag2; /* 8: Flags #2: reserved */
Uchar flag3; /* 9: Flags #3: reserved */
Uchar crtr; /* 10: Created by:
14H = HDFORMAT
42H = xtrs mkdisk
80H = Cervasio xtrshard port to Vavasour M4 emulator */
Uchar dfmt; /* 11: Disk format: 0 = LDOS/LS-DOS */
Uchar mm; /* 12: Creation month: mm */
Uchar dd; /* 13: Creation day: dd */
Uchar yy; /* 14: Creation year: yy (offset from 1900) */
Uchar res1[12]; /* 15 - 26: reserved */
Uchar dparm; /* 27: Disk parameters: (unused with hard drives)
bit 7: Density: 0 = double, 1 = single
bit 6: Sides: 0 = one side, 1 = 2 sides
bit 5: First sector: 0 if sector 0, 1 if sector 1
bit 4: DAM convention: 0 if normal (LDOS),
1 if reversed (TRSDOS 1.3)
bit 3 - 0: reserved */
Uchar cyl; /* 28: Number of cylinders per disk */
Uchar sec; /* 29: Number of sectors per track (floppy); cyl (hard) */
Uchar gran; /* 30: Number of granules per track (floppy); cyl (hard)*/
Uchar dcyl; /* 31: Directory cylinder [mkdisk sets to 1; xtrs
ignores, but value must be correct if image is
to be used with Reed emulators.] */
char label[32]; /* 32: Volume label: 31 bytes terminated by 0 */
char filename[8];/* 64 - 71: 8 characters of filename (without extension)
[Cervasio addition. xtrs actually doesn't limit this
to 8 chars or strip the extension] */
Uchar res2[184]; /* 72 - 255: reserved */
} ReedHardHeader;
See also¶
xtrs(1)
http://www.tim-mann.org/trs80/dskspec.html
Authors¶
mkdisk was written by Timothy Mann (see
http://tim-mann.org/).
The floppy file formats here called JV1 and JV3 were developed by Jeff Vavasour
for his MSDOS-based Model I and Model III/4 emulators (respectively). They
have become a de facto standard in the TRS-80 emulation community, and much
TRS-80 software is available on the Internet in .dsk format. Thanks to Jeff
for designing and documenting the formats.
The format here called DMK was developed by David Keil for his MSDOS-based Model
4 emulator. This format has the advantage that it can represent essentially
everything the original TRS-80 floppy disk controllers can write, including
all forms of copy protected disk. Thanks to David for designing and
documenting this format.
The hard drive format was developed by Matthew Reed for his MSDOS-based Model
I/III and Model 4 emulators. I have duplicated his format to allow users to
exchange .hdv hard drive images between
xtrs and Matthew's emulators.
Thanks to Matthew for designing the format and providing documentation.