HP 82901M 5.25in 270K FDD: Difference between revisions

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To decode flux data from a raw image of an internal 5.25" disk, you can use the following {{Archive web|url=https://github.com/keirf/greaseweazle|name=Greaseweazle}} diskdef to properly decode it<pre>
To decode flux data from a raw image of a LIF 5.25" disk, you can use the following {{Archive web|url=https://github.com/keirf/greaseweazle|name=Greaseweazle}} diskdef to properly decode it<pre>
disk hp.lif.40dd  
disk hp.lif.40dd  
     cyls = 33
     cyls = 33

Revision as of 00:41, 2 July 2023

HP 82901M 5.25in 270K FDD
General Info
Release Year 1980
Manufacturer HP
Condition Working
Identifiers
Model Number 82901M
QR Code
(Click for Asset Tag)

This is a dual 5.25" floppy drive for HP systems from the late 1970s and early 1980s.. It's HP-IB interface and Amigo protocol makes it compatible with a large number of HP computers, for example the HP 9836C Technical Computer & HP 85.

Floppy Disk Drives

The internal floppy drives are standard Shugart interface compatible drives, the example I have used Tandon TM200-2A drives. As such a drive emulator like a Gotek can be used in place of them.

Both of the drives are jumpered at MX on U1E, the left drive has DS0 set and the right DS1 as described in the Tandon Manual[1]. A Termination pack is also installed in the drive at the end of the shared cable in U2F.

Controllers of floppy drives from 89201A showing jumpers and termination pack setup.

Disk Structure

Double Density 5.25" disks used in the system are formatted with a LIF filesystem using 33 tracks, 16 sectors per track, and 256 bytes per sector for a total capacity of approximately 270KiB. The LIF filesystem measures usage in blocks, these disks have a total block size of 1056.

HxC Disk map of floppy disk for 9836 showing 33 tracks with 16 sectors Disk Image Sample Files


To decode flux data from a raw image of a LIF 5.25" disk, you can use the following Greaseweazle (archived) diskdef to properly decode it

disk hp.lif.40dd 
    cyls = 33
    heads = 2
    tracks * ibm.mfm 
        id = 0 
        interleave = 1 
        secs = 16
        bps = 256
    end
end

Note that sector's are 0 indexed requiring id = 0

Repairs - Modifications

Caps Wiki Page

2023-06

  • Large power supply capacitors reformed
  • Standoffs for right drive repaired with epoxy after damaged in shipping
  • Bearings for disk spin hub/flywheel re-lubricated after being seized
  • FAIL - Discovered right floppy drive top head is bad, replacement needed

External Projects and Software

Related Devices

External links

  1. ↑ Page 26 of "OEM OPERATING AND SERVICE MANUAL TMIOO-l, TMIOO-2 DISK DRIVES 48 TRACKS PER INCH" in the Tandon Manual (archived)
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