CMD-HD
| CMD-HD | |
 | |
| Type: | Hard drive |
| Producer: | CMD |
| Price: | US$ 599.95-1299.95 US$ |
| Released: | 1990 |
| Discontinued: | 2001 |
| Processor: | |
| Memory: | |
| OS: | |
| Info: | Various storage capacities: 20 MBytes to 2 GBytes. |
The CMD-HD (actually HD Series) is an external hard disk drive for the C64 / 128 developed by Creative Micro Designs (CMD ) was produced from 1990 to around 2001.
It consists of a SCSI adapter designed for the C64 and a then commercially available internal SCSI hard disk in a housing with its own power supply unit, as well as several connections for operation on the C64 / 128 and a SCSI Port for additional SCSI devices.
It works with JiffyDOS, but its speed advantage can only be used if JiffyDOS is installed in the computer's Kernal. Internally it works with the so-called Boot-ROM, which is housed in an EPROM and the HD-DOS in the system partition.
The CMD-HD offers a parallel connection which establishes the connection to a RAMLink and increases the transmission rate even further. As a cable for the parallel connection, those of the external floppies from the Atari-ST fit.
The drives 1541, 1571, 1581 can be emulated, which are created as partitions on the hard disk. Native partitions can also be created, the size of which can be freely defined by the user in 256 - block steps. A native partition can have a maximum of 16 Mbytes. ([1 to 255] tracks * 256 blocks or sector s * 256 bytes). A total of 255 partitions can be set up (partition no. 0 is already occupied by the system partition). Thus, the HD-DOS can manage a maximum of 4 GBytes. However, you need the last published Boot ROM version (2.80) to be able to operate a hard disk with a capacity of more than 1 GByte.
The CMD-HD was available with different storage capacities from 20 MBytes to 2 GBytes. The first hard drives by CMD were sold in 1990, 20 MByte for about US $ 599.95, 40 MByte for US $ 799.95 and 100 MByte for US $ 1299.95. From the mid-1990s, there were also models with a capacity of 1 GB.
Additional SCSI devices can be connected to the SCSI connection. This was achieved with additional hard drives to increase capacity, the Zip drives popular in the late 1990s, and CD-ROM drives. With the software CDROM-Commander , the latter gave the user the option of extracting disk image s from data CDs directly on the C64 onto the hard disk. There was also a program that could play audio CDs. The audio sound must be tapped at the audio output of the CD-ROM drive.
It is possible to replace the internal SCSI hard disk with a CF card (with SCSI-IDE adapter and IDE-CF card reader).
In addition, the CMD-HD offered a real-time clock, which was buffered by a battery.
Pictures[edit | edit source]
Partition and file formats[edit | edit source]
With HD track and sector access, it is important to remember that the track and sector layout conforms to the norm of the partition type in which the access takes place. This method allows the HD to become compatible. If an access occurs in an emulation mode partition, the track and sector layout of the partition is identical to the drive it is emulating. The tables in this section determine which tracks and sectors are present in each partition type and where the header, BAM and directory blocks are located. This section also provides information about the BAM format and directory entries, as well as the format of the various file types.
1541 emulation mode partitions[edit | edit source]
Sectors per track[edit | edit source]
| SECTORS PER TRACK (1541 EMULATION MODE) | ||
|---|---|---|
| TRACKING AREA | SECTOR AREA | TOTAL |
| 1 - 17 | 0 - 20 | 21 |
| 18 - 24 | 0 - 18 | 19 |
| 25 - 30 | 0 - 17 | 18 |
| 31 - 35 | 0 - 16 | 17 |
Directory header[edit | edit source]
| HEADER (1541 EMULATION MODE) TRACK 18 SECTOR 0 | ||
|---|---|---|
| BYTE | CONTENT | DESCRIPTION |
| 0 | 18 | Track of the first directory block |
| 1 | 1 | Sector of the first directory block |
| 2 | 65 | ASCII character A for format type |
| 3 | 0 | 1541 emulation mode |
| 4 - 143 | ||
| 144 - 161 | Disk name, padded with shifted spaces | |
| 162 - 163 | Disk ID | |
| 164 | 160 | Shifted spaces |
| 165 | 50 | ASCII representation of 2 for the DOS version |
| 166 | 65 | ASCII representation of A the format type |
| 167-170 | 160 | Shifted spaces for separation |
| 171 - 220 | 0 | zeros - reserved |
| 221-255 | 0 | zeros reserved |
BAM (first block)[edit | edit source]
| BAM (1541 EMULATION MODE) TRACK 18 SECTOR 0 | ||
|---|---|---|
| BYTE | CONTENT | DESCRIPTION |
| 0 | ||
| 1 | ||
| 2 | 65 | ASCII character A for format type |
| 3 | ||
| 4 - 143 | BAM for tracks 1-35 (4 bytes per track) | |
| 144 - 161 | ||
| 162 - 163 | Disk ID | |
| 164 | ||
| 165 | ||
| 166 | ||
| 167-170 | ||
| 171 - 220 | ||
| 221-255 | ||
BAM (first Block)[edit | edit source]
| BAM (1541 EMULATIONS-MODUS) SPUR 18 SECTOR 0 | ||
|---|---|---|
| BYTE | DESCRIPTION | |
| 0 | Number of free sectors on the track | |
| 1 | Number of unused blocks for sectors 0-7 | |
| 2 | Number of unused blocks for sectors 8-15 | |
| 3 | Number of unused blocks for sectors 16-23 | |
| NOTES: | The LSB (low bit) in each byte (1-3) shows the status of the lowest sector that is covered by the byte. A binary value of 1 indicates that the sector is free, 0 indicates that it is occupied. | |
1571 emulation mode partitions[edit | edit source]
Sectors per track[edit | edit source]
| SECTORS PER TRACK (1571 EMULATION MODE) | ||
|---|---|---|
| TRACKING AREA | SECTOR AREA | TOTAL |
| 1 - 17 | 0 - 20 | 21 |
| 18 - 24 | 0 - 18 | 19 |
| 25 - 30 | 0 - 17 | 18 |
| 31 - 35 | 0 - 16 | 17th |
| 36 - 52 | 0 - 20 | 21 |
| 53 - 59 | 0 - 18 | 19 |
| 60 - 65 | 0 - 17 | 18 |
| 66 - 70 | 0 - 16 | 17th |
Directory header[edit | edit source]
| HEADER (1571 EMULATION MODE) TRACK 18 SECTOR 0 | ||
|---|---|---|
| BYTE | CONTENT | DESCRIPTION |
| 0 | 18 | Track of the first directory block |
| 1 | 1 | Sector of the first directory block |
| 2 | 65 | ASCII character A for format type |
| '3' | '128' | '1571 emulation mode' |
| 4 - 143 | ||
| 144 - 161 | Disk name, padded with shifted spaces | |
| 162 - 163 | Disk ID | |
| 164 | 160 | Shifted spaces |
| 165 | 50 | ASCII representation of 2 for the DOS version |
| 166 | 65 | ASCII representation of A the format type |
| 167-170 | 160 | Shifted spaces for separation |
| 171 - 220 | 0 | zeros - reserved |
| 221-255 | ||
BAM (first block)[edit | edit source]
| BAM (1571 EMULATION MODE) TRACK 18 SECTOR 0 | ||
|---|---|---|
| BYTE | CONTENT | DESCRIPTION |
| 0 | ||
| 1 | ||
| 2 | 65 | ASCII character A for format type |
| 3 | ||
| 4 - 143 | BAM for tracks 1-35 (4 bytes per track) | |
| 144 - 161 | ||
| 162 - 163 | Disk ID | |
| 164 | ||
| 165 | ||
| 166 | ||
| 167-170 | ||
| 171 - 220 | ||
| '221 - 255' | 'Number of free sectors for tracks 36-70 - one byte per track' | |
BAM (further blocks)[edit | edit source]
| BAM (1571 (PAGE 2) EMULATION MODE) TRACK 53 SECTOR 0 | ||
|---|---|---|
| BYTE | CONTENT | DESCRIPTION |
| 0 - 104 | BAM for tracks 36-70 (3 bytes per track) | |
| 105 - 255 | 0 | zeros - reserved |
BAM input format[edit | edit source]
| BAM INPUT FORMAT (1571 (page 1) EMULATION MODE) Byte format 4-143 on track 18, sector 0 4 bytes per track: Bytes 4-7 cover the track 1, bytes 8-11 cover track 2, ... | |
|---|---|
| BYTE | DESCRIPTION |
| 0 | Number of free sectors on the track |
| 1 | Number of unused blocks for sectors 0-7 |
| 2 | Number of unused blocks for sectors 8-15 |
| 3 | Number of unused blocks for sectors 16-23 |
| NOTES: | The LSB (low bit) in each byte (1-3) shows the status of the lowest sector that is covered by the byte. A binary value of 1 indicates that the sector is free, 0 indicates that it is occupied. |
BAM input format[edit | edit source]
| BAM-INPUT FORMAT (1571 (page 2) EMULATION-MODE) Byte format 0-104 on track 53, sector 0 3 bytes per track: Bytes 0-2 cover track 36, bytes 3-5 cover track 37, ... | |
|---|---|
| BYTE | DESCRIPTION |
| 0 | Number of unused blocks for sectors 0-7 |
| 1 | Number of unused blocks for sectors 8-15 |
| 2 | Number of unused blocks for sectors 16-23 |
| NOTES: | The LSB in each byte (0-2) is used to indicate the status of the lowest sector that is covered by the byte. A binary value of 1 indicates that the sector is free . A binary value of 0 indicates that the sector is occupied. In bytes 221-225 of track 18, sector 0, the associated byte for the number of free sectors is stored. |
1581 emulation mode partitions[edit | edit source]
Sectors per track[edit | edit source]
| SECTORS PER TRACK (1581 EMULATION MODE) | ||
|---|---|---|
| AREA | SECTOR AREA | TOTAL NUMBER |
| 1 - 80 | 0 - 39 | 40 |
Directory header[edit | edit source]
| DIRECTORY HEADER (1581 EMULATION MODE) TRACK 40, SECTOR 0 | ||
|---|---|---|
| BYTE | CONTENT | DESCRIPTION |
| 0 | 40 | Track of the first directory block |
| 1 | 3 | Sector of the first directory block |
| 2 | 68 | ASCII characters from D for format type |
| 3 | 0 | Reserved |
| 4 - 21 | Disk name, padded with shifted spaces | |
| 22-23 | Disk ID | |
| 24 | 160 | Shifted spaces for separation |
| 25 | 51 | ASCII characters of 3 for DOS version |
| 26 | 68 | ASCII characters from D for format type |
| 27-28 | 160 | Shifted spaces for separations |
| 29 - 255 | 0 | zeros reserved |
BAM (first block)[edit | edit source]
| BAM BLOCK1 (1581 EMULATION MODE) TRACK 40, SECTOR 1 | ||
|---|---|---|
| BYTE | CONTENT | DESCRIPTION |
| 0 | 40 | Track of the next BAM block |
| 1 | 2 | Sector of the next BAM block |
| 2 | 68 | ASCII characters from D for DOS version |
| 3 | 187 | Complement of the version number |
| 4 - 5 | Disk ID | |
| 6 | 192 | Not used by the HD (1581 default) |
| 7 | 0 | Tag for auto-load file |
| 8-15 | 0 | Reserved |
| 16-255 | BAM for tracks 1-40 (6 bytes per track) | |
Partition and file format comparison[edit | edit source]
The formats of the partitions and the file formats differ in the individual partition types. In this section these differences are shown graphically in the form of a diagram. The partitions of a 1541, a 1571, a 1581 and a native partition are compared with each other.
Sectors per track in partition comparison[edit | edit source]
Directory in partition comparison[edit | edit source]
BAM in partition comparison[edit | edit source]
