HELP!!!! :-) The so-called "Mode X" 2

[AmkG]

I've somewhat recently discovered a weird little mode called "Mode X" which is not really a separate mode but another way of accessing Mode 13h (and its undocumented 360x240x256c variant mode). The video card expects the data in mode 13h to be sequential from plane-to-plane, so that you can access at most 1 plane at a time, but in ModeX you access it in the same way that you access a 16 color mode, that is, at most all 4 planes at a time. So you can get a speed boost of up to 4x (although practically you can get only up to 2x since you don't always need to access four sequential pixels). Now the questions:

1. I don't really know how to set the Mode X. I think you can just ask BIOS to set it to mode 13h first, then set the C4 or CHAIN4 flag in one of the registers. Is this correct, or do I need to do something else (I just need a 320x200 screen)?
2. Is it possible to access the high-res SVGA modes using the same Mode X scheme? That would be mighty nice.

Thanks in advance, AmkG "Information has a tendency to be free. Which means someone will always tell you something you don't want to know."

 

[BinaryBob]

You know an easy way to avoid all this? Read Micheal Abrashes Graphic Programmers Black Book, and you will have hit gold for VGA programming. ModeX is dealt with in there. It may take you a while to get there, but when you do you will know 10 times what you do now. Try it. I have.

 

[AmkG]

Problem is it's kinda difficult for me to look for books... most of those here in the Philippines deal with things like Java and IT programming which I'm not very interested in... Also, it seems to be a rather old book (can you tell me what approx. year it was published?). Anyone have any other suggestions?

Darn I think I saw a book with "also covers Mode X!" on the cover, except I was ignorant of that at that time so I didn't buy it... "Information has a tendency to be free. Which means someone will always tell you something you don't want to know."

 

[Wody]

Hello,

Download this book:
Graphics Programming Black Book
by Michael Abrash

http://www.ddj.com/articles/2001/0165/0165f/0165f.htm?topic=graphics

It probably has more then you want to know. Wouter Dijkslag

http://www.wody.demon.nl