Modified Atari 1050 rom?

[Jack Tseng]

Can we modify the Atari 1050 rom? I need to format the double density, use
26 sectors per track instead of 18. 90K is increased to 130K. Can 180K be
increased to 260K?

Thanks!
Jack Tseng

[Thomas Richter]

Jack Tseng wrote:
> Can we modify the Atari 1050 rom? I need to format the double density, use
> 26 sectors per track instead of 18. 90K is increased to 130K. Can 180K be
> increased to 260K?

Well, "it can", but the trouble is elsewhere. Double density really
means 256 bytes per sector, not 128 bytes per sector as usual. The
trouble with 128 bytes per sector is that a shorter sector size includes
more overhead to indicate the start of the sector, the sector and track
number and so on, overhead that is not visible otherwise. This
additional overhead reduces the payload that is available, and thus is
the reason why enhanced density provides less capacity than double density.

Now the reason why the 1050 is not capable of double density even though
the disk controller is is simply because the 1050 has only a total of
256 bytes(!) RAM on board. 128 bytes are used for the sector buffer, and
the remaining bytes are used by the CPU to work with. Thus, it is pretty
tough to extend the 1050 to double density without extending the
hardware in one way or another.

So long,
Thomas

[Rick Cortese]

Thomas gave a good explanation. There is a home brew 1050 US Doubler
mod where all you do is add a 6810 and burn the USD code into an EPROM.
Problem is now the 6810 is getting pretty hard to find.

Bob Wooley showed some interest in the 1050 since it used the 2793/2797
disk controller chip it should be able to do anything from 3.5" to 8"
floppies.
But then came the XF551 and SIO2PC and after hacking/promoting those
he kind of moved on to more challenging stuff.

Rick