What was the mod to the Applle IIe "rev A" board that enabled Double Hi-Res (DHR) graphics?

[ross.dykes]

Hi all,

I have a question that may very well be answered somewhere on this forum if I was smart enough to find it. What was the modification done to the first model of IIe to enable double-hi-res graphics?

I have what appears to be a "rev A" IIe with a copyright of 1982 on the board without double-hi-res support:

which doesn't matter much as I have the green Monitor III display. However, my son wants to use Apple II desktop on this thing to make it easier to launch games, and that requires DHR. Is it possible to mod the "A" board to support DHR?

 

[VERAULT]

The board also cannot use the ENHANSED chipset with 65C02 as well. Nice board, I have yet to see a 1982 rev A in person.

 

[ross.dykes]

Interesting. I have heard you can upgrade the ROMs and install a 65C02 if you want to, but it won't affect the inability to display DHR. I guess the mousetext font additions are pointless without DHR anyway?

 

[VERAULT]

If I had that board I would leave it as is as they are pretty uncommon.

 

[ross.dykes]

Yeah, no desire to mod anything after reading more about how the rev B board works, seems like it's more than something that can be put on a protoboard and stuck in a slot. So no DHR graphics for me! =)

 

[VERAULT]

I owned a couple Apple II RGB Boards which had instructions specifically for Rev A 1982 boards. Since they worked in tandem with the 80 col card or in place of it.. Its possible they remedied the issue. I dont know for sure as I dont own a Rev A board.

take a look at one of them here: https://forum.vcfed.org/index.php?t...kb-on-a-stock-apple-iie-the-hard-way.1243480/

 

[ross.dykes]

Ah cool! It's possible I suppose, since that (and presumably other RGB cards?) effectively bypasses the on-board video generation circuitry. That particular card would lack the memory to do 80 col though. - EDIT: I just saw the pic of the box that says it has 80 col support, so I stand corrected!

I remember reading that one of the Apple II VGA card projects out there would add DHR support to just about anything because it had its own memory for shadowing what was on-board the Apple II and thus didn't care about accessing the correct bank to display graphics. I did order a VGA card to play with, will be interesting to see what it does.

 

[VERAULT]

Incorrect. It can do 80col. It just cant get the system to 128Kb

 

[ross.dykes]

Yep caught that after I posted. Derp.