1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
|
mkdisk(1) General Commands Manual mkdisk(1)
Name
mkdisk - make a blank emulated floppy or hard disk for xtrs, or
add/remove an emulated write-protect tab
Synopsis
mkdisk -1 [-f] filename
mkdisk [-3] [-f] filename
mkdisk -k [-s sides] [-d density] [-8] [-i] [-f] filename
mkdisk -h [-c cyl] [-s sec] [-g gran] [-d dcyl] [-S] [-f] filename
mkdisk {-p|-u} {-1|-3|-k|-h} filename
Description
The mkdisk program is part of the xtrs package. It has two distinct
functions:
+ It can make a blank (unformatted) emulated floppy or hard drive
in a file.
+ 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
xtrs(1) for background information.
The conventional file extensions are .dsk for emulated floppies and
.hdv for "HDV" 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.
By default, when creating disk image files, and if the system's under-
lying fopen(3) library function supports this ISO C11 feature, mkdisk
refuses to overwrite an existing file called filename. The -f
("force") option overrides this default, "clobbering" filename.
Making Emulated Floppies
With the -1 flag, mkdisk makes an unformatted emulated floppy of type
JV1. Besides -f, 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. Besides -f,
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 sin-
gle-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 5.25" drive. Setting -s1 or -d1 saves space after
the floppy is formatted; setting -8 consumes additional space. Speci-
fying -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 number dcyl marked for
use as its directory.
You will usually want to use the default values for all these parame-
ters. 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 (XTR-
SHARD/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 con-
troller 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 parti-
tion, 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 emu-
lator too), sec must always be divisible by 32, because we always emu-
late 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 cylxsec 256-byte sectors. The image file starts out
small and grows as you write to more cylinders. The allocation effi-
ciency 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
space wasted due to fragmentation but limits the maximum size of the
drive.
Seeing that the maximum unpartitioned drive size is less than 13 MiB
and that the maximum granule size is only 8 kiB, 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.
Embedding the file name in a hard disk image
Matthew Reed's hard drive image file format contains an eight-character
field for storing the filename of the hard drive image itself. mkdisk
simply uses the given filename as this within-image filename. This
works best if filename specifies a short file name in the current work-
ing directory. Since modern operating systems permit filenames much
longer than eight characters, historically versions of mkdisk would
deliberately "spill" the remaining characters of filename into the
reserved structure field following the filename (see Technical data,
below).
There were two problems with the foregoing approach:
+ Modern versions of the standard C library such as glibc will
detect the overflow of the destination buffer, emit a lengthy,
technical, frightening diagnostic, and abort the program immedi-
ately. mkdisk itself offered no explanation.
+ mkdisk also did not do any checking to see if the filename
string copy might overflow the subsequent buffer, the reserved
area.
Now, mkdisk by default writes a truncated (if necessary) copy of file-
name to the hard disk image file header; a warning diagnostic is emit-
ted in that event.
With the -S option, mkdisk simulates the old behavior, up to the end of
the reserved area. In this "spill mode", a warning diagnostic is emit-
ted if spillage occurs, and the program aborts with an error if the
filename is too long to fit in the filename and reserved fields com-
bined.
For maximum portability of your hard drive images, use only ASCII-
encoded eight-character filenames in the current working directory.
Omit control characters in the range \x00-\x1f and \x7f. These are not
"8.3" file names; the "." character, if used, counts toward the eight-
character limit.
Write Protection
With the -p flag, mkdisk turns on write protection for an existing emu-
lated floppy or hard drive. It turns off all Unix write permission
bits on the file, and (except for JV1 floppies) also sets a write-pro-
tected 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 per-
missions. 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 sec-
tor 0, ...). It can represent only single-sided, single-density flop-
pies. 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 in Common File
Formats for Emulated TRS-80 Floppy Disks <http://www.tim-mann.org/
trs80/dskspec.html> at Tim Mann's TRS-80 site. A copy of this HTML
file is also included in the xtrs distribution.
The DMK format was documented in a file on David Keil's web site, now
available via the Internet Archive <https://web.archive.org/web/
20010128070200/http://discover-net.net/~dmkeil/trsdoc.htm#Technical>;
this file is also included with his emulator. Some points are worth
bearing in mind, particularly if you're attempting to work with copy-
protected TRS-80 disks:
+ If neither the single-density nor the 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.
+ 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 reed.h):
/* Matthew Reed's hard drive format. Thanks to Matthew for providing
documentation. The comments below are copied from his mail
messages, with some additions. */
/* $Id: reed.h,v 1.2 2008/06/26 04:39:56 mann Exp $ */
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, but HDFORMAT sets 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 [xtrshard/dct ignores for now]
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);
gran (hard) */
Uchar dcyl; /* 31: Directory cylinder [mkdisk sets to 1;
xtrs ignores] */
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;
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 MS-DOS-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 MS-DOS-
based Model 4 emulator. This format has the advantage that it can rep-
resent essentially everything the original TRS-80 floppy disk con-
trollers 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 MS-DOS-
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.
See also
xtrs(1)
Common File Formats for Emulated TRS-80 Floppy Disks <http://www.tim-
mann.org/trs80/dskspec.html> by Tim Mann; a copy may be locally avail-
able with your xtrs installation at /usr/share/doc/xtrs/dskspec.html.
xtrs 2017-04-16 mkdisk(1)
|
