[Coco] OS9 Lv 1 games

[Tormod Volden]

On Wed, Sep 28, 2016 at 4:37 PM, John W. Linville wrote:
> On Tue, Sep 27, 2016 at 08:12:39PM -0500, David Ladd wrote:
>> On Tue, Sep 27, 2016 at 7:51 PM, Barry Nelson <
>> barry.nelson at amobiledevice.com> wrote:
>>
>> > Cave Walker does not run on NitrOS9 L2 on physical hardware, but strangely
>> > does run on NitrOS9 L2 on VCC. It runs on OS-9 L2 on physical hardware
>> > fine, and when run that way it takes advantage of some CoCo 3 features.
>> >
>>
>> Barry, that is strange that a NitrOS-9 L2 and Cave Walker doesn't work on
>> real hardware. I know Cave Walker does work on real hardware through OS-9
>> L2.  Wonder what could be causing the issue with NitrOS-9 L2?
>
> More importantly, if it doesn't work on physical hardware then
> why does it work on VCC?

One thing that is different is the use of bitbanger code versus Becker
interface code. The former uses a few more bytes, maybe enough to
cross a 256 byte boundary and cause further changes in memory
allocation and so forth. Of course, timing will also be different.
Interrupts are turned off during DriveWire I/O but if the program is
somehow synced with a periodic interrupt the duration of the I/O can
determine at which point the next interrupt kicks in, maybe triggering
a stack overflow in one case but not the other...

>
> Is VCC the only emulator with this breakage? Or does it work on MAME,
> etc as well?
>

It would have been nice to have an emulation of the bitbanger interface.

Tormod