[Coco] Largest supported HDD size?

Robert Gault robert.gault at att.net
Wed Nov 30 09:56:29 EST 2016

RETRO Innovations wrote:
> My google fu must be lacking tonight, as I thought it would be trivial to see
> how big a HDD is supported on the Coco via an IDE or SCSI interface, but I came
> up empty.
> I figured the CocoSDC can use an unlimited drive, as you mount images by name,
> but what about the GLenside IDE or the various SCSI systems?  Is it really 255
> drive images * 170kB, or is there another limit?
> Jim


I have an old article on the Cloud9 site showing how RGBDOS/HDBDOS can use 
drives with multiple partitions of 256 "drives".

As Bill Pierce mentioned, LSN0 of an OS-9 drive has a maximum of 3 bytes to 
indicate the number of sectors on the drive. However, if you use the same trick 
in the above article, you could have multiple OS-9 partitions with a new driver.

I wrote a driver to access OS-9 "disks" in the Basic partition of a hard drive. 
By extension, that driver could read multiple OS-9 partitions limited by the 
ability to handle the math of adding the offset to the sector LSN#.


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