Pixel plotting or bank switching problem

[Lionel Pinkhard <lionelpi@mweb.co.za>]

Hi,

I'm having a little problem plotting a pixel to the screen! I can't believe this! But anyways, this is the function I'm using:

	static void plotpixel(int x, int y, char color) {
		asm {
			mov ax, y
			mov cx, 640
			mul cx
			add ax, x 
			mov bx, ax
		}
		setbank(_BX >> 16);
		asm {
			mov ax, 0a000h
			mov es, ax
			mov ax, bx
			mov di, ax
			mov ax, color
			mov [es:di], ax
		}
	}

I'm not sure whether this is the exact function, I don't have the code in front of me, but it's something similar, anyway. Also, I think the problem might be with the bank switching (I'm using 640x480x256). This is my bank switching code:

	void setbank(int bank) {
		static int activebank;
		if (activebank == bank) return;
		asm {
			mov ax, 4f05h
			mov bx, 0h
			mov dx, bank
			int 10h
			mov ax, 4f05h
			mov bx, 1h
			mov dx, bank
			int 10h
			mov ax, bank
			mov activebank, ax
		}
	}

The plotting function is similar to what I use in Mode 13h, with the exception of calling the setbank() function to set the bank. So I think it's in the setbank() function. I wrote this function without much knowledge of how it works, I only did some research on VESA, and worked this out, so it might not be doing anything at all!

Anyways, this it was happens when I run (AFAIK anyway):

	It sets mode 640x480x256, then it loads the palette (these two functions seem to be working, so I didn't include them), and then it dumps me back to the console. I (purposely) didn't switch back to Mode 3h, so I noticed that the palette DID indeed change (you quickly notice it if you see that the MS-DOS Editor is green and brown!). So any ideas?

Thanks in advance,

Lionel Pinkhard

P.s. The program is supposed to draw a circle, but I don't see a single pixel!
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