This is easy project. Especially if you have the original IBM tech reference manual. You will need to interface both the memory interface from the ISA connector and the I/O interface from the bus. The memory lines are used to write the screen image, either the character/attribute info. Or the color pixel information. The I/O portion is used primariy to program the 6845 crt timing generator chip.

If you are going to the trouble of making this unterface you may want to consider using a VGA card instead. The interface is quite similar and there a good books available that describe the VGA. At 640 x 480 the VGA is scan rate compatatible with a TV monitor (similar to the CGA) but would give you a far better picture. You should be able to entirely ignore the VGA bios on a VGA board.

If you go the VGA route and are interested in looking at PC software I wrote before that interfaces the VGA ports and runs the
board in graphics mode with an overlay character mode done in the graphics I could share all that software with you to look at. It is in a combination of Borland C and 8086 assembler.

Have Fun....
sounds like a fun project.
Do consider the Cygnal parts. One of the newer ones has a development board that is about $150 ... but the part I am thinking about has the full external bus interface as well as a full complement of peripherals and lots of port lines...seven ports I think if you count those that the external interface is on. The part has 128K FLASH, 8K XRAM on-board and runs at like 25/50 MIPS.....It would run a VGA board as well as any old 8 MHz PC/AT ever did or as good as a 25 MHz 386/SX !!!!!

Here is the like to the part...

http://www.cygnal.com/products/C8051F124.htm


Mike Karas