[Coco] CoCo SDC Harddrive Mode

[Allen Huffman]

> On Mar 30, 2017, at 9:39 AM, Barry Nelson <barry.nelson at amobiledevice.com> wrote:
> 
> The commands cobbler and os9gen work much better on images that are single sided and have 18 sectors per track. I use the format below with my CoCo SDC for the OS9 “hard disk", it has 20480 tracks:

Good to know someone did the work to figure out how big you can go.

The problem in Cobbler stems from ten size of the DAM (disk allocation table). It will allocate the size of the DAM plus 255 or 256. So, if you max out your DAM for a 128MB 1-sector per cluster maximum hard disk size, the DAM is FFFF and it tries to allocate FFFF+256 RAM without any error checking, causing the problem.

A simple fix would be to have it just scan through the DAM in smaller chunks, which is the approach our MultiBoot software did when linking bootfiles for multiple DOS bootfiles.

One day, I'll look at doing this.