[Coco] values other than 0 or 1 for byte 14 of decb dir entry

[Robert Gault]

Arthur Flexser wrote:
> On Mon, Mar 26, 2012 at 1:32 AM, Robert Gault<robert.gault at att.net>  wrote:
>> One aside. CoCoMaxIII will not work with RGBDOS nor HDBDOS. You need a pure
>> Tandy DOS.
>
> I believe I ran into something like this with Extended ADOS-3 and CoCo
> Max 3.  Turned out to not be a code incompatibility at all, but an
> incompatibility with using a 16K 27128 EPROM in the controller.  If
> I'm recalling correctly, even standard Tandy Disk Basic is
> incompatible with CoCo Max 3 if it is burned into a 27128 rather than
> an 8K EPROM.  Seems CoCo Max 3 looks for the disk ROM code to start at
> $E000 rather than $C000 which doesn't affect anything if you are using
> an 8K EPROM on account of ghosting, but crashes CoCo Max 3 if a 16K
> EPROM is in use.
>
> This incompatibility is fixable with a single-byte change to CoCo Max
> 3, I believe.  The Ext. ADOS-3 documentation may have this fix in it.
>
> Art
>

You've got a great memory Art but the fix does not help with RGBDOS. The fix in 
the ADOS-3 manual changes line 165 in the BOOT.BAS and BOOTRS.BAS programs for 
CoCoMax but that is not enough. You also have to disable ADOS-3. There is no way 
to disable RGBDOS. I don't believe you can disable HDBDOS.

As for the EPROM, I use a 27C256 with 4 different contents. Only with RGBDOS 
switched in will CoCoMaxIII not work.

I'll take a look at the CM3 code that line 165 patches to see if I get any ideas.