# Hard Disks

BeebEm supports emulated SCSI, SASI and IDE hard disks. You can only have one of either SCSI or IDE hard drive enabled at a time.

There are some preformatted ADFS disk images in the DiscIms folder. The disks can be used in Model B (you will need to add a suitable ADFS ROM to the ROM configuration, see below), B Plus or Master 128 mode. To use the disk images enable hard drive emulation on the Hardware menu and press `A` + `F12` to boot in ADFS mode (ignore the error for drive 4 if in Master mode). The hard disks then appear as drives 0 to 3. Floppy disks can still be accessed as drives 4 and 5.

You need to use the ADFS 1.30 ROM (BBC) and ADFS 1.50 ROM (Master) to use the SCSI interface, and the ADFS 1.33 ROM (BBC) and ADFS 1.53 ROM (Master) to use the IDE interface. HADFS 5.30 and later use the IDE interface.

There are 4 10MB pre-formatted ADFS SCSI disk images in the DiscIms folder (the scsi?.dat files). There are 4 4MB blank IDE drive images in the DiscIms folder (the ide?.dat files).

There are some demo tunes in scsi0.dat which you can listen to with the PLAY program.

There is also the sasi0.dat file which is a Torch Z80 hard disc image (see the Torch Z80 section).

You can use the Hardware → Select Hard Drive Folder menu option to select an alternative folder containing hard disk image files. The folder should contain scsi?.dat, sasi?.dat or ide?.dat files, together with corresponding .dsc files.

Use the Options → Save Preferences menu option to save the setting to the BeebEm Preferences.cfg file.

Note that if you replace the scsi?.dat files, the scsi?.dsc files may also need changing to configure the size of the hard disk image. Bytes in the scsi?.dsc file used by BeebEm (with offsets starting at 0):

- Byte offset 13 = number of cyclinders (high byte)
- Byte offset 14 = number of cyclinders (low byte)
- Byte offset 15 = number of heads

The number of 256 byte sectors in the hard disk image is calculated as:

> Sectors = heads * (cyclinders high byte * 256 + cyclinders low byte) * 33