Philip Pemberton wrote:
Does anyone know what the typical range of floppy and
ST506/ST412 drive
track-to-track seek rates is?
When I worked at Apparat around 1981, the
company's main products were
for the TRS-80. Shugart tried to get us to sell a cost-reduced floppy
drive. I don't recall their model number, but it had two major
differences from the normal SA400. It was built on a bent sheet metal
frame instead of an aluminum casting, and instead of a stepper motor for
head positioning, they used a solenoid mechanism similar to an 8-track
player. The direction line on the interface did nothing, and each step
pulse moved the positioner inward by one track, until it reached track
34. The next step pulse would cause the positioner to return to track 0.
If I recall correctly, the normal track-to-track time was specified at
around 400 ms, and the "restore" time at around 1000 ms.
You couldn't use the normal seek and restore commands of a 1771/179x
controller with this, so you had to rely on the step in command. Normal
FDC drivers in TRSDOS, NEWDOS, etc. wouldn't work, so we would have had
to supply a modified OS with it.
Our conclusion was that even though the drive was slightly less
expensive than a normal drive, there would be essentially *zero*
customer demand for it.
I don't think I've heard of a "real" floppy drive with more than 15 ms
track-to-track seek time, nor an ST-506 interface drive with more than 5
ms. There is also a settling time required after a seek, which can be
up to 15 ms, but that isn't required for each step.