Altair FDC+ Firmware Release v1.5

Discuss construction, troubleshooting, and operation of the Altair 8800c computer

Altair FDC+ Firmware Release v1.5

Postby AltairClone » June 13th, 2021, 11:07 am

I have posted version 1.5 of the FDC+ firmware at the link below. The update affects only drive type 4, "Soft 5.25 inch as 8 inch". Primarily, the update adds support for disk drives that suppress index pulses while seeking. The newer the drive is, the more likely it is to suppress index pulses while seeking. A jumper on the drive to enable/disable this option was phased out with newer drives as well.

This increases the number of 5.25" HD drives that can work with the FDC+ as drive type 4. It also allows some 3.5" drives to work as drive type 4. The 3.5" drive must have an option to spin at 360 rpm in addition to the default 300 rpm mode.

Much thanks to alank2 for pushing for this update and for providing invaluable test data from his workbench and logic analyzer. ...

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