View Single Post
Old 16th Oct 2017, 3:20 pm   #1
JohnBHanson
Heptode
 
Join Date: Aug 2009
Location: Worthing, Sussex, UK.
Posts: 661
Default Alphatronic PC rejuvenated

I have rejuvenated my Alphatronic PC by replacing the old 40 track 5.25 inch disk drives with "Modern" 3.5 inch DD/HD disk drives.

I have also modified the disk controller to cope with the high density mode of these disk drives increasing the storage capacity by a factor of 4.

One of the problems was the floppy disk contoller was located in the same case as the first floppy drive. Its PCB was mounted under the floppy and designed so the tall capacitors of the power supply were behind the floppy drive. I needed an adapter board to change the connector from the edge connector type used for the 5.25 inch connector to the type used on the 3.5 inch drives. This had to be very small so as to fit between the drive and the capacitors. A *big* thank you to volte-face for supplying this.

I also had to modify the bios and boot roms to allow booting from HD disks. While doing this I decided to add code to the boot roms to allow booting from 512 byte sector disks as well as the original 256 byte sector disks in both HD and DD modes. This allows me to easily use a usb floppy drive to copy the data to/from a PC.

Details of what I have done can be found at
http://81.105.120.101/alphatronic/hw...h_density.html

I first got this machine in about 1984 and nice to have it working again!
JohnBHanson is offline