Re: Where's the CPM files
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Hi Allison,
Welcome back!??
There has been an issue with my implementation of CP/M on both the S100 JAIR board and the Z80MC. I failed to understand one of the drive buffer spaces needed, the space needed to create a bit map of the clusters used/free. I followed the examples in the CP/M books and used 31 bytes which is the size required for the SSSD disks of 256,256 bytes.
I have now rewritten the BIOS to expand these buffers to 512 bytes, enough for 8Meg disk file images.
The BIOS uses SD Card FAT-16 format to reach the data on the Card.? I could have just used the SD Card in it's raw form, but then you'd need special programs to access the card from a computer.? Since I still use PC's, I choose to use the well established FAT-16.? The BIOS can read and write data into the FAT-16 disk images, but it cannot create any FAT-16 files or extend those files.? It doesn't know how to look for a free cluster and add it to the file chain, or even how to change the file size.? It simply uses the space of the file as it's already allocated in the FAT-16 table.? The BIOS counts through the clusters of the image file as CP/M counts through the sectors and tracks.? There is no skewing, it's 1 to 1.??
I will send you the files directly rather than waste space in the 1802 forumn.
Cheers,
Josh
On Tuesday, December 5, 2023 at 09:20:54 a.m. EST, ajparent1/kb1gmx <kb1gmx@...> wrote:
Hello all...
She's back!
It been a while and life intervened...? One of the things was getting a Z80MC to play with.
I have over a dozen CP/M systems and a few of my own creation both hardware and
highly modified software. CP/M is a very malleable OS and can support more than
most think or have tried.
So now I have a real Z80MC and the software is done is such a way as to be different
from the BIOS and loaders of my experience.? Back then it was floppy, hard disk,
Eprom based, and of course IDE/CF based,? With that FAT was never a consideration.
I find FAT too tightly tied to PCs and equally as fragile as? CP/M allocation scheme.
The other is that FAT offers a hierarchical file system and CP/M can't/doesn't use it.
It something I'd like to add to CP/M, that is a way to like from one device/Drive
to another (especially on large media).
The other is my system the typical disk is 8MB (or 32mb for ZRDOS) and multiple
partitions.? ?
If all goes well it will be a self development environment for a simpler OS like
NSDos, the goal there is to release it from hardware NS* MDS hard sector disk.
So it will be a playground for experiments started in some case over 45 years ago.
Allison
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