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

[mmarlett at isd.net]

Robert,

Good research but...With the stated problems of the GIME and it has an
update, why would you want to run a buggy chip?

I doubt that modules will be created so that NitrOS-9 will run on it. If so
the distrubution would be 87GIME so you either fix it by your method, or
why fight it and just get a fixed GIME.

?? Nice to have this documented and the work you and others have supplied.

Thoughts????

Mark

>This is a message for everyone who is unable to run NitrOS-9 on a Coco3 
>with a 1986 GIME chip.
>
>As background, there are two versions of the GIME, 1986 & 1987. The '86 
>chip was the cause for many articles on "sparklies" that plagued early 
>adopters of the Coco3. There were also problems with the verticle and 
>horizontal scroll registers. I just found out that it is next to 
>impossible to boot NitrOS-9 (any version) on an '86 GIME Coco3.
>
>There are several theories that try to explain this problem and present 
>ways to correct it. To date, none have been successful during my testing 
>of the problem. The short story is that there are mistakes in the 
>circuits of the '86 GIME that can't handle the stress of NitrOS-9 code. 
>The strange aspect of this problem is that occasionally the boot process 
>completes and NitrOS-9 then runs without problems.
>
>I have found a workaround that seems to give 100% success at booting 
>NitrOS-9 on an '86 GIME Coco3. Change the boot screen from 40 or 80 
>character width to 32. You can still boot to an 80 character wide /term 
>as this has no effect on stability. The boot screen is still in a Coco3 
>video mode rather than Coco1, so why this works is still a mystery.
>
>                         !!!HOW TO DO IT!!!
>It is only necessary to change one byte in sector 1 of track 34 to get a 
>successful boot. This changes the module REL. Once booted, you can 
>os9gen a fresh boot disk from the current NitrOS-9 release using the 
>rel_32 module if desired. Using the new module will then have the 
>NITROS9 BOOT
>   (FAILED)
>message in the correct location on the screen. The one byte patch will 
>prevent the message from printing, although the diagnostics will still 
>be readable.
>
>Using either a PC disk editor, an OS-9 disk editor (dEd), or one for 
>Disk Basic, locate in T34S1 the bytes $6C 00 00 00 09 00 00 00 '0B or 
>03' and '34 or 24'. It is the last byte in this sequence, $34 or $24, 
>that needs to be changed to $20. You don't need to bother with the crc 
>bytes and once booted you ought to create a new boot disk with a proper 
>rel_32 module.
>
>If you don't have a disk editor for Disk Basic, you can manage the same 
>thing with DSKI$ and DSKO$
>
>
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