[sebhc] Graphics Card

Walter Moore waltm22 at comcast.net
Tue May 15 22:05:35 CDT 2007

>2. Northwest Digital "Graphics Plus GP19"
>This board mounted just like the Imaginator, either in the unused 
>CPU slot of an H19 or horizontally above the CRT in an H89. It also 
>connected exclusively to the H19's terminal logic board.
>The Graphics Plus *replaced* the TLB's video RAM with 32k of video 
>RAM. The TLB's 6845 CRT controller could be set for different modes 
>of operation; character modes were 80x25 (standard), plus 64x32, 
>80x50, 132x25, and 132x50. It was amazing to see 132 characters per 
>line and 50 lines of text on an H19/H89! The graphic modes were 
>512x250 and 512x500.

My GP-19 still works and is sometimes hooked up to my H8.  This is 
the prototype we used to develop the GP-19.  It's still fun to see it 
in 132 column mode - it's great for looking at assembler 
listings.  Set the page length to 49 and an entire page is 
visible.  The same 16K of RAM was used for both text mode and 
graphics mode.  In text mode, you could scroll back and look at text 
which had rolled off the top of the screen (took that from an HP system).

When/if I ever get some 8" drives working, I can put the source in 
the archive if anyone is interested.  I should also have the original 
H19 source in MACRO-80, and a modified H19 source which added some 
nice features and improved the speed a lot, also in MACRO-80.


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