[Coco] micro drive configuration

Roger Taylor operator at coco3.com
Tue Oct 13 23:28:25 EDT 2009

I have an idea here that I need some feedback on in case I'm missing 
something that might sneak up on me too late.

Take a 2 gig "memory card" of any kind that the CoCo is interfaced to 
and can access raw sectors for the memory and treat it as a "drive" 
for OS-9 or Disk BASIC.  Currently, there may be systems in use that 
use partitions to mark off an OS-9 area and a Disk BASIC area, or 
possibly other areas.  I'm guessing that they 256-byte sector 
controllers so that 1/2 of the memory card isn't lost.  If the 
sectors are 512 bytes, then the OS probably uses both halves of the 
sector which requires extra overhead... which I'm about to talk about.

What if the memory card and host controller only dealt with 512-byte 
sectors.  Would it be absolutely silly to let OS-9/NitrOS-9 have the 
first half of the sector from LSN to LSN(end) and Disk BASIC have the 
2nd half of the sector from LSN0 to LSN(end) ?  I realize that a 
read/write is involved for every write to retain the other OS'es 
sector, and that a certain amount of speed would be lost for the 
overhead.  The benefit would be that a 128mb, 256mb, 1gig, or 2gig 
(just examples) memory card can be dropped in without having to tell 
the CoCo "OS" anything about partitions or areas to stay out of.  The 
idea is to use the drive in a parallel fashion and in the simplest 
fashion, with no BASIC config program having to be used to configure 
the "drives".  A 2 GIG card would yield 1 GIG for OS-9/NitrOS-9 and 1 
GIG for Disk BASIC virtual drives, but then only 256 drives are ideal 
so this is what I'm trying to work around without wasting any "hard 
drive" space.

Of course OS-9 and DIsk BASIC both would have to use only 256 byte sectors.

~ Roger Taylor

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