[Coco] Important Announcement: NitrOS-9 & 1986 GIME

[Robert Gault]

Roger Taylor wrote:

><snip>
> Yes.  :)
> 
> The 1986 GIME chip is not really buggy if the software doesn't know how 
> to adapt to what it requires.
> 
> The fact that the new NitrOS-9 can't run on such a CoCo 3 is not a 
> hardware flaw, but something that should be fixed totally from 
> software.  A test can be performed during boot that would let the system 
> know which GIME chip is installed, and then correct whatever software 
> flaw is causing this problem.
> 
> Has anyone tried consulting with Sockmaster?  He's a genious with the 
> GIME chips and the differences between the 1986 and 1987 versions.
> 
> -- 
> Roger Taylor
> 
> 

I don't know if Sockmaster has followed this discussion but I don't 
think anyone has tried to contact him on the subject.

There are several problems with your point of view. The first is that 
having tried many different changes to the NitrOS-9 code under the 
assumption there the '86 GIME works as described in the service manual, 
nothing tried makes any difference. That does not mean nothing will 
work, but I feel this is a dead end based on my tests.

Two, there is no doubt that the '86 GIME does not conform to the 
information in the service manual and that this is the reason for the 
'87 update. Even the simplest of GIME operations can cause screen 
flashes, the scroll registers don't always work as stated, and there is 
probably more wrong. Since Tandy has not released a corrected set of 
specs for the '86 GIME and it does not conform to the service manual, 
the chip must be considered buggy.

Three, NitrOS-9 does indeed run on a Coco with the '86 GIME. It just 
does not boot reliably when the boot screen is 40-80 columns. You might 
say that means it doesn't run but consider what actually happens. 100% 
reliable boots from a 32 col. window with no other changes to the code 
except a value stored at $FF99. The exact same code has about a 10-20% 
chance in a 40-80 col. window. That does not conform to the Coco3 specs.

I don't completely agree with Mark. If the only change needed for 
NitrOS-9 is booting from a 32 col. window for any Coco3 system to work, 
that is the way to go. This in no way is an inconvenience to NitrOS-9 
operation because there is no restriction on the width of the initial 
screen after the boot finishes. There is no need for a test to determine 
which version of the GIME is present. I do agree with Mark that if '87 
GIME chips are available, users should purchase them because the Coco3 
will then perform to specs. However, realistically we should not assume 
that any more GIME chips are available. Any user can choose to boot from 
40-80 col. screens but the distribution package should use 32 columns.

There is a completely different issue regards GIME chips and the special 
graphics programs that you and Sockmaster write. Here the different 
video timings must be taken into account for the graphics programs to 
give best results. That is not a bug, where the Coco has a complete 
crash, but optimization.