UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Gemini 80-Bus System

JohnBHanson · 22nd Oct 2019, 2:18 am

35 track drives have the same track spacing as 40 track drives - which is double that of an 80 track drive. So reading a 35track disk can be done witha 40 track or 80 track drive. In PC terms that is either a 360k drive or a 1.2M drive.

Gemini formats has a shortish lead in from the index hole to the start of the first sector and this can cause problems with 765 floppy controllers.

The only real z80 machine I have is a matmos/alphatronic PC - and it has a 765 disk controller. I have written a multi-format bios for it. I have upgraded its floppy disks to 1.44 MByte 3.5 inch drives having had problems with its original floppies from the early 80s deteriorating. I do have plans to add other drives at some point - its a matter of building the cables and cases at some point.

22nd Oct 2019, 2:18 am	#250
JohnBHanson Heptode Join Date: Aug 2009 Location: Worthing, Sussex, UK. Posts: 661	Re: Gemini 80-Bus System 35 track drives have the same track spacing as 40 track drives - which is double that of an 80 track drive. So reading a 35track disk can be done witha 40 track or 80 track drive. In PC terms that is either a 360k drive or a 1.2M drive. Gemini formats has a shortish lead in from the index hole to the start of the first sector and this can cause problems with 765 floppy controllers. The only real z80 machine I have is a matmos/alphatronic PC - and it has a 765 disk controller. I have written a multi-format bios for it. I have upgraded its floppy disks to 1.44 MByte 3.5 inch drives having had problems with its original floppies from the early 80s deteriorating. I do have plans to add other drives at some point - its a matter of building the cables and cases at some point.