Any way to run 32X VDP without hurting MD mapping?

Fonzie · Post by **Fonzie** » Wed Dec 06, 2006 10:04 am

Hi,

I just wanted to know if it was possible to use the 32x VDP without going (or having) the crappy genesis re-mapping...

PowerOn 32X > INIT/VDP > Shutdown 32x (but keep VDP output) > Run genesis game.

I think they did re-mapping to avoid interrupts timing problems on 68K if the SH is reading the cartridge... Any inputs?

I'm asking that because (if it is possible), we could load a display engine in 32x RAM, run it... Then run standard genesis genesis game keeping the 32x active.
Who never dreamt about a faster Herzorg Zwei with 256c backgrounds?

Thx.

Stef · Post by **Stef** » Wed Dec 06, 2006 12:02 pm

I think that if 32X is disabled, you just can't access his parts :-/

Fonzie · Post by **Fonzie** » Wed Dec 06, 2006 4:26 pm

So, even if the sh2 started to run code, if i disable 32x, sh2 will stop?
So bad ...

Stef · Post by **Stef** » Wed Dec 06, 2006 9:22 pm

Not tested on real hardware but i think it will operate like this.
I can actually test rom on real hardware if you need it

ob1 · Post by **ob1** » Wed Jan 24, 2007 3:17 pm

The 68000 mapping relies on ADEN. Reset, you've got the usual mapping, set, you've got the alternate mapping.
I don't know if, once set, it can be reset without problem ...

Fonzie · Post by **Fonzie** » Thu Feb 01, 2007 5:03 pm

YEah, ADEN is the key... but it would be great if setting ADEN to 0 (after intializing SH2 and letting them running from their ram) don't stop them...

There is a small chance... I can't wait to see a confimation/disconfirmation of this.

You know, I have in mind a project that would run original genesis game code (aden = 0) with a little hack to set some display process to the 32x (in total transparency).

I have in mind a great game named Z*** T****** that wouldn't suffer from a bigger screen display

Or a easier one : H****** Z*** that wouldn't suffer from a 256 colors background

If you get what i mean... :'(

ob1 · Post by **ob1** » Mon Feb 05, 2007 1:43 pm

The Hardware Manual states that, once it (ADEN bit) has been set, further "change (is) not allowed".

Stef · Post by **Stef** » Mon Feb 05, 2007 1:53 pm

The ADEN means ADaptator ENable bit. If set to 1, the 32X is enabled and you can use it. If you set it to 0 (and if it's allowed to do it), i'm afraid you just can't use anymore the 32X hardware...