3.5" Altair CP/M

[Allison]

Grant Stockly wrote:
> I have a tarbell floppy controller card that has been rewired to access 
> 3.5" disks using a standard PC 3.5" disk drive.  I have 3 disks that the 
> Altair can boot off of and read, but my windows computer can't do 
> anything with them.  I've tried rawread.exe and diskinfo.exe and they 
> both choke on the disk.  I assumed that if a disk could be written with 
> the standard 3.5" disk drive on the tarbell card then it should also be 
> read on the same drive connected to a modern IBM compatible.
> 
> The disks are 720K style, they don't have the high density hole.
> 
> I was hoping that these disks would be an easy way to move data to and 
> from the Altair.
> 
> The version of CP/M is 1.4.
> 
> What could be missing?  If the bitrate is fixed, then is CP/M not 
> writing standard sectors?  Rawread says "Address not found" and diskinfo 
> says the drive is not ready.
> 
> Grant
> 
> 

The tarbel card is the single density version or is a double density one?
One way to tell is 1771 single density only, 1791 or 1793 double density capable.

If single density then some PCs FDC cannot do SD, some can.

Allison