[Coco] GIME text modes and font data

John Kent jekent at optusnet.com.au
Mon Sep 3 22:00:47 EDT 2012

On 4/09/2012 6:32 AM, jdaggett at gate.net wrote:
> On 4 Sep 2012 at 3:04, John Kent wrote:
>> I'm sure most people on the list know all this.
>> I'm reasonably familiar with the chips in the CoCo 1 & 2, although I'm not
>> really up with all the registers in the GIME chip.
> The GIME chip is not 100% backward compatible with the 6847/6883 combo. There are
> semigraphics modes that are not supported at least in software. I also think not in hardware.
> On the COCO1/2 the SAM chip generates the clocks to the MPU and the VDG clock. The
> VDG chip does have an onboard address generator for video memory access but is limited to
> only 13 bits or 8K of video memory. The VDG syncs the SAM chip for HS and VS and
> address timing. Similar happens inside the GIME as this has been integrated into one chip.

OK thanks James,

It's been a little while since I looked at the data sheets.



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