HP 9122C Dual 1.44MB Floppy Drive

HP 9122C

General Info
Release Year	1989
Manufacturer	HP
Condition	Working
Identifiers
Model Number	9122C
Power Requirements
Input Voltage	120/240 VAC
Power Connector	IEC C13
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High Density 3.5" floppy drive using HP-IB interface to connect to HP computers. This drive uses HP's CS80 protocol for communicating with the computer.

Setup Notes

To get the most out of one of these with a Series 200 computer you will need a HP 98625 Disc Interface and HP 98620A DMA Controller which extend the system hardware to allow for faster access and booting from CS80 drives like this.

Floppy Disk Drives

The internal drives of my 9122C were Sony MP-F37W-50 drives. These drives have switches on the side for setting a drive ID rather than using a twist in the cable. This also means both drives spin whenever accessing either one.

These drives are also powered through the ribbon cable. This makes them incompatible with other systems and not easy to replace with other drives.

On the left you can see the separate connections to the pins that would normally all be ground.

Disk Formats

There are a large number of disk formats supported by this drive. Shown are the default formats for High and Low Density disks. They use 77 tracks with 256 bytes per sector, but low density disks are 16 sectors while high density are 32 sectors. Note that both formats also create a 78th formatted track at track 79, the purpose of this track is not yet known but may be related to booting the disk.

• 

  Disk formats table from the manual for the HP 9122C floppy drive.

• 

  Default low density disk format for 9122C, 77 tracks, 16 sectors, 256 bytes/sectors. ~630KiB capacity. Disk Image Sample Files Note track 79 is also formatted with two unformatted tracks before it.

• 

  Default high density disk format for 9122C, 77 tracks, 32 sectors, 256 bytes/sectors. ~1.2MiB capacity. Disk Image Sample Files Note track 79 is also formatted with two unformatted tracks before it.

To decode flux data from a raw image of a 9122C disk, you can use the following Greaseweazle (archived) diskdefs to properly decode DD and HD images

disk hp.lif.80dd                                                                 
    cyls = 77                                                                    
    heads = 2                                                                    
    tracks * ibm.mfm                                                             
        interleave = 2                                                           
        secs = 16                                                                
        bps = 256                                                                
    end                                                                          
end                                                                              
                                                                                 
disk hp.lif.80hd                                                                 
    cyls = 77                                                                    
    heads = 2                                                                    
    tracks * ibm.mfm                                                             
        interleave = 2                                                           
        secs = 32                                                                
        bps = 256                                                                
    end                                                                          
end

Repairs - Modifications

2023-06

• Internal Sony floppy drives were stuck do to grease sticking
• Drive disassembled and cleaned to make work

Related Devices

• HP 9836C
• HP 98625 Disc Interface