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CP/M-68K and FAT File System
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Tom Szolyga
Dec 16, 2022, 2:24:29 PM12/16/22
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I am trying to run CP/M-68K on a ROSCO 68K SBC. The issue is the ROSCO ROM boot code only understands a FAT formatted disc and will only boot from a FAT disc. This ROSCO boot code loads a file called ROSCOBOOT.BIN into memory at 4000 hex and executes it. This app can load any .BIN file and execute it. CP/M-68K has it's own disc format that is not compatible with FAT. The question is how to boot CP/M-68K?
I have written an app that is loaded and executed by the ROSCO Boot app. It has the binary files for CCP, BDOS and BIOS inside the app. It relocates these files to high memory and executes them. CP/M-68K starts and runs until it tries to do a disc operation. It fails because the disc is FAT. This is close, but no cigar.
What is the disc was formatted with two partitions? The first partition would be FAT and rather small. The second partition would be the rest of the disc but not formatted. CP/M-68K would boot as above. All of the CP/M disc drives would be in the unformatted area. These virtual discs would be defined with a track offset that is the size of the FAT partition. in this way, the two file systems could co-exist and ignore each other.
Thoughts???
I have written an app that is loaded and executed by the ROSCO Boot app. It has the binary files for CCP, BDOS and BIOS inside the app. It relocates these files to high memory and executes them. CP/M-68K starts and runs until it tries to do a disc operation. It fails because the disc is FAT. This is close, but no cigar.
What is the disc was formatted with two partitions? The first partition would be FAT and rather small. The second partition would be the rest of the disc but not formatted. CP/M-68K would boot as above. All of the CP/M disc drives would be in the unformatted area. These virtual discs would be defined with a track offset that is the size of the FAT partition. in this way, the two file systems could co-exist and ignore each other.
Thoughts???
David Schultz
Dec 16, 2022, 4:01:18 PM12/16/22
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On 12/16/22 1:24 PM, Tom Szolyga wrote:
> What is the disc was formatted with two partitions? The first partition would be FAT and rather small. The second partition would be the rest of the disc but not formatted. CP/M-68K would boot as above. All of the CP/M disc drives would be in the unformatted area. These virtual discs would be defined with a track offset that is the size of the FAT partition. in this way, the two file systems could co-exist and ignore each other.
> Thoughts???
Works for me. Except that I would use the loader version of CP/M-68K in
> What is the disc was formatted with two partitions? The first partition would be FAT and rather small. The second partition would be the rest of the disc but not formatted. CP/M-68K would boot as above. All of the CP/M disc drives would be in the unformatted area. These virtual discs would be defined with a track offset that is the size of the FAT partition. in this way, the two file systems could co-exist and ignore each other.
> Thoughts???
the FAT file system. Then changes to CPM.SYS could skip messing with
that again.
--
http://davesrocketworks.com
David Schultz
Bill Shen
Dec 17, 2022, 8:10:03 AM12/17/22
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On Friday, December 16, 2022 at 12:24:29 PM UTC-7, tszo....net wrote:
> What is the disc was formatted with two partitions? The first partition would be FAT and rather small. The second partition would be the rest of the disc but not formatted. CP/M-68K would boot as above. All of the CP/M disc drives would be in the unformatted area. These virtual discs would be defined with a track offset that is the size of the FAT partition. in this way, the two file systems could co-exist and ignore each other.
Yes, use the offset to skip over non-CPM disk area is the easiest way. My own implmentation has system programs/utilities in the non-CPM disk area. They are directly accessible as long as the LBA addresses and program length are known.
> What is the disc was formatted with two partitions? The first partition would be FAT and rather small. The second partition would be the rest of the disc but not formatted. CP/M-68K would boot as above. All of the CP/M disc drives would be in the unformatted area. These virtual discs would be defined with a track offset that is the size of the FAT partition. in this way, the two file systems could co-exist and ignore each other.
Bill
Randy McLaughlin
Dec 17, 2022, 11:41:05 AM12/17/22
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Quick and dirty do the above using an offset.
Right answer put the cpm loader in small fat directory and have the BIOS read the MBR and have CPM partitions for the CPM drives.
It is much easier to use a fixed offset.
Randy
Right answer put the cpm loader in small fat directory and have the BIOS read the MBR and have CPM partitions for the CPM drives.
It is much easier to use a fixed offset.
Randy
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