S100 Computers

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Processor Technology -
This was an early S-100 bus FDC set of boards produced before the Western Digital LSI 1771/9x chips became widespread.  It was a two board set.

Helios-II Controller    

Processor Technology Formatter

The FDC communicated with the 8080 CPU via DMA on the bus. I/O ports F0-F7H were utilized.  Port F0H was the status port, F1H the command port. Ports F3H & F4H set the length of data in bytes, ports F5H and F6H  set the transfer address. Port F7H commanded the drives themselves.  8" Persci drives were utilized along with a hard sectored disk.  
Processor Technology very early on saw the need for a floppy disk system.  Initially their disk system was popular. The Disk operating system PTDOS was quite encompassing at the time with their own BASIC and a storage capacity of 386K/disk.  However as the reliability of the Persci drives came into question, the appearance of the LSI 1791 FDC chip and the general trend towards soft sectored disks (particularly 5" disks) the system fell out of favor.  Nevertheless properly "tuned" the Helios-II system was a joy to work with.

Sol+Disk Drives

The large but very detailed manual explaining the whole system can be obtained here.


Other Processor Technology S-100 Boards
4K RAM   8K RAM   48K RAM   16K Dynamic RAM    1702 EPROM     3P+S    CUTS    GPM   VDM-1  Helios-II FDC


This page was last modified on 10/25/2013