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I've Got VGA Output!!

A project log for ISA 8-Bit Video Experiments

A Series of Experiment to Create an ISA 8-Bit Video Card

Dave's Dev LabDave's Dev Lab 10/22/2019 at 14:462 Comments

After a considerable amount of debugging, (with the help of @agp.cooper and @Alastair Hewitt ) I was able to get solid 40x30 text output from my 8-bit video board! I'm using a 8x16 font with the resolution of 640x480@60Hz and driving it with a pixel clock of 12.5875MHz, which is within the range of the clock speeds supported for the MC6845. I've got a ton of stuff to test before making a new revision of the board, but..... it works!

Discussions

antenn wrote 11/04/2020 at 14:50 point

“cga snow” effect will be observed when writing to video memory from the system bus. The circuit needs write buffering or a wait signal while crtc accessing video memory.

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Dave's Dev Lab wrote 10/06/2021 at 03:19 point

yeah i am doing static writes to the memory at this stage so i am not experiencing any "snow" effects, but yes, i intend to work on the wait signal similar to what was implement in the PCjr system....

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