*** X64 (X64 and VICE emulator image files)
*** Document revision: 1.3
*** Last updated: March 11, 2004
*** Contributors/sources: Jouko Valta
This file type, created by Teemu Rantanen, is used on the X64 emulator (a
UNIX-based emulator) which has been superceeded by VICE. Both Vice and X64
support the X64 file standard, with Vice also supporting the regular D64
and T64 files.
X64 is not a specific type of file, but rather encompasses *all* known
C64 disk types (hard disk, floppies, etc). An X64 is created by prepending
a 64-byte header to an existing image (1541, 1571, etc) and setting
specific bytes which describe what type of image follows. This header has
undergone some revision, and this description file is based on the 1.02
version, which was the last known at the time of writing.
The most common X64 file you will see is the D64 variety, typically
174912 bytes long (174848 for the D64 and 64 bytes for the header, assuming
no error bytes are appended). The header layout (as used in 64COPY) is as
follows:
00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F ASCII
----------------------------------------------- ----------------
0000: 43 15 41 64 01 02 01 23 00 00 00 00 00 00 00 00 C.Ad...#????????
0010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ????????????????
0020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ????????????????
0030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ????????????????
0040: XX XX XX <- standard C64 image starts here....
Bytes:$00-03: This is the "Magic header" ($43 $15 $41 $64)
04: Header version major ($01)
05: Header version minor ($01, now its up to $02)
06: Device type represented ($00)
$00=1540 See note below...
$01=1541 (Default)
$02=1542
$03=1551
$04=1570
$05=1571
$06=1572
$08=1581
$10=2031,4031
$11=2040,3040
$12=2041
$18=4040
$20=8050
$21=8060
$22=8061
$30=SFD-1001
$31=8250
$32=8280
07: Maximum tracks in image (only in version 1.02 or greater)
1540/41/70: 35
1571: 35
1581: 80 (Logical single-sided disk)
08: Number of disk sides in image. This value must be $00 for
all 1541 and 1581 formats.
$00=No second side
$01=Second side
09: Error data flag. I assume that if this location has any
non-zero value in it, this will indicate the existance of
the error bytes. For a description of the error bytes, see
the D64 topic dealing with extended formats.
0A-1F: Unused, set to $00
20-3E: Disk image description (in ASCII or ISO Latin/1)
3F: Always set to $00
40-: Standard C64 file begins here
The first four bytes used for the device type at position $06 ($00 to
$03) are functionally the same, and are compatible with older version of
X64 files. Some old X64 files might have $00 for the device type (instead
of $01), but it makes no real difference.
As most instances of X64 files will be strictly 1541 images, bytes 08-3F
are set to zero, and some versions of the X64 emulator don't use bytes
08-3F.
There is no advantage for PC users to use this format since virtually no
PC emulator that I know of uses them, and for the most part, it provides
the same functionality as a D64 file.
In order to read a generic X64 file, first you must determine that it is
an X64, and then determine the type of file it contains. In effect, you
have to double-decode the file, which makes support a little more
difficult. Also, you would have to be able to work with *all* of the types
of drives that X64 supports, a daunting task.
Its only advantage is that is encompasses all of the standard disk
formats on the C64. If other disk types were common (like 1581 or CMD
disks), then this format might be more popular.
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