Tandom TM100 5¼-inch Floppy Disk Drive

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The Tandom TM100 series of 5¼-inch floppy drives were full height devices and were offered in several configurations. The drives were used in IBM 5150 and 5160 Personal Computers (with a custom 'IBM' bossed faceplate), and many other machines besides.

In common with most 5¼-inch drives, the drives had no outer casing as such, and so could easily be damaged when servicing.

Models

Model	Type	Tracks	Tracks-per-inch (TPI)	Formatted Capacity
TM100-1	Single sided	40	48TPI	180KB
TM100-2	Double sided	40	48TPI	360KB
TM100-3	Single sided	80	96TPI	360KB
TM100-3M	Single sided	80	100TPI	360KB
TM100-4	Double sided	80	96TPI	720KB
TM100-4M	Double sided	80	100TPI	720KB

The "M" suffix may have been used for the 100TPI varients as Micropolis had produced a 100TPI drive early on.

Jumpers

TM100 Logic Board

• Programmable Shunt Socket (1E):
  • HS - unused; must be cut
  • DS0..DS3 - Drive select
  • MX - multiplex; used only in single-drive systems when drive logics should remain enabled at all times. Must be cut in a multi-drive system.
  • (Spare)
  • HM - unused; must be cut
• R50/R51 - Selects power save mode via 0-ohm resistor:
  • R50 - 3.8W saving at idle, by removing 200mA current to stepper motor when drive is not selected
  • R51 - no power save mode
• W1 - Side Select:
  • Open - single-sided (TM100-1)
  • Closed - double-sided (TM100-2)
• W2/W3 - Write Flip-Flop Control:
  • W2 closed, W3 open - Disables set and preset lines on write flip-flop only during internal N Write
  • W2 open, W3 closed - Dsiables set and preset lines on the write flip-flop continuously
• W4/W5 - Write Protect Control:
  • W4 closed, W5 open - Write Protect Control responds to a write-protected disk
  • W4 open, W5 closed - Write Protect Control is inhibited
• W6/W7/W9 - LED Control:
  • W6 closed, W7/W9 open - LED controlled by Drive Select
  • W6 open, W7/W9 closed - LED controlled with N In Use (J1-4)
• W8 - Drive Select 3 Enable (DS3 disabled if open)
• W10 - Door Lock (lock is disabled if open)

The drives had a standard 14-pin DIP socket (RP1) for a terminator resistor network (for example a Beckman 899-3-R150).

Reliability

• Soft Error Rate: One error per 10⁹ bits read
• Hard Error Rate: One error per 10¹² bits read
• Seek Error Rate: One error per 10⁶ seeks
• MTBF: 8000 Power-on-hours under typical usage (25% duty cycle)
• Media Life: 3 x 10⁶ Passes per track and 30,000 insertions
• Head Life: 20,000 media-contact hours

Reference Materials

• Tandom TM100-1 and TM100-2 Service Manual
• Tandom TM100-4 Product Specification
• Adjusting the Radial Alignment a Tandon TM100-2A Drive Without an Alignment Disk

See Also

• Floppy Disk Drive Cable Termination and Device Addressing
• IBM Personal Computer 5150 and IBM Personal Computer XT 5160