My next step is to get to the base raw SD initialization and read/write.
The idea is more compact code that has no fat artifacts or code needed
to handle it as fat. to me other than a few keep out areas the 1gb sd is
just a bag of 2,097,152 (0x200000) blocks of 512 bytes.
The idea is to have a super directory (tag and bag) of smaller
CP/M sized (8mb or smaller)? "disks" that can be loaded as needed.
Each would be file system only.? ?The CP/M OS is loaded from
EProm as pseudo boot track.? The?CP/M file systems can be loaded
on the fly as its an offset and DPH/DPB that describe the media.?
SELDISK in the BIOS selects a drive (up to 16) but usual systems
limit that due to buffer space and ALLOC space (256 byte per
8MB using 4K alloc) needs. But the base number of drives can be
altered on the fly and its a minor coding task to make that a loadable
system variable rather than BIOS fixed? as done often.
By doing that it become easy to make a really large device usable.
Seems to work fine for 128 or 256mb CF.
PC comparability for the SD is not used as files needed are simply
transferred via USB-serial to Z80MC.? By treating the SD as a
non removable memory it lightens the code.? Doing that allows for a
monitor, tag and bag OS, BIOS, CP/M image (62K system) plus
extras to fit in 32K eprom.
This is a result of thinking outside of the CP/M alteration guide
and 4 floppies.
Allison
