[Coco] CoCoSDC under NitrOS9

[Dave Philipsen]

Well, I started with Allen’s 128 MB image and I used a binary editor under Windows and expanded it to 1 GB.  Then I put the dsk file on the SD card and mounted it.  From OS9 I dmode’d the descriptor for /sd1 and changed the # of cylinders from 007F to 07FF.  Then I formatted it (OS9 format verified the size of 4+ million sectors before I started the format).  Then I did a cobbler /sd1 which correctly copied the boot file to it but had an error because it couldn’t correctly write the boot track.  Then I put the SD card in a reader and started diddling around with a binary editor in Windows.  The boot track always resides at the logical position of track 34 (sector $264??) so I found the boot track on the 128 MB image (starts with the letters ‘OS’ or $4F53).  I copied the boot track out of the 128 MB image and into the 1 GB image.  You have to remember that even though the boot track gets put at the same offset (sector $264??) the disk allocation map is different because the 1GB image uses 8 sectors/cluster instead of one.  So you have to manually calculate where to set the bits in the allocation map so the operating system won’t overwrite the boot track.  

Anyway, I’m just going mostly by memory but I guess I could do a write-up describing exactly how I did it.

http://www.davebiz.com/images/1GB.jpg


Sent from my iPad

> On May 30, 2018, at 7:05 PM, Travis Poppe <travispoppe at gmail.com> wrote:
> 
> I'm curious how you managed the 1GB bootable VHD?
> 
>> On Tue, May 29, 2018 at 3:33 PM Dave Philipsen <dave at davebiz.com> wrote:
>> 
>> Thanks to Allen Huffman I've been running a bootable NitrOS9 image on my
>> CoCoSDC for some time now.  Recently I increased the size of the image
>> and I now have a bootable 1GB partition for NitrOS9.  So now I would
>> like to be able to mount and unmount images from NitrOS9.  Does anyone
>> if any documentation exists for the CoCoSDC (short of disassembling the
>> SDC DOS) that would facilitate me in writing some utilities under
>> NitrOS9 for this?
>> 
>> Dave
>> 
>> 
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