HP 9122C Dual 1.44MB Floppy Drive

From Tech Tangents
Jump to navigation Jump to search
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
QR Code
(Click for Asset Tag)


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.

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

Video Appearances

External Projects and Software