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Tarbell Electronics -- 1011A Floppy Disk Controller

Tarbell Electronics followed their popular Cassette Interface with this FDC.  

Tarbell Electronics FDC

The Tarbell Floppy Disk Interface was a programmed-data-transfer (not DMA) device utilizing Port I/O, similar for example to the SD Systems Versafloppy boards. It was designed to work with a variety of standard-size floppy disk drives. It includes a 32-byte ROM bootstrap program, which was automatically enabled when the computer RESET button was pushed, and which switched itself out after the bootstrap had run. In this way, no part of the computer 64K of memory needed to be dedicated to Read-Only-Memory (ROM).

The interface ran at the standard speed of 250,000 bits per second, and the normal formatted capacity per diskette of 256 kilobytes. Places for two connectors were provided on the board. One 50-pin header connector and a cable with the mating connector were provided with the interface kit. The drive end of the cable has no connector, but a 50-pin edge connector could be added for an extra $10.00.

There were four extra IC slots to allow you to do your own thing, and the connector pins come out to jumper pads, so you can adapt to different drives. The manual had the connections detailed for popular drives.

An on-board dip-switch was used to select the device address, disable the bootstrap, and write-protect things. Circuitry was included to run up to four drives, and eight could be accessed by using the spare IC slots. The Tarbell Floppy Disk Interface and other related items could  be bought in pieces, so that was not necessary to make a single large outlay of cash. 

The board utilized the Western Digital 1771-01 chip.

Tarbell also offering the (then new) CP/M floppy disk operating system separately that was setup to work with the drive.

The very detailed and well written manual for this board can be obtained here.

Other Tarbell Electronics S-100 Boards
Cassette Interface     Single Density FDC      Double Density FDC       32K RAM      Z80 CPU Board


This page was last modified on 06/06/2015