Vsync and Hsync from the cartridge port?

[KillerBean2]

I was studying the MegaDrive schematics i order to think up some new crazy modifications to do, when I came across two pins on IC8 labeled "Vsync" and "Hsync". I thought: "Yes!!! This smells like a VGA mod!", but when I followed the signals to their origin, they turned out to come from the cartridge port (B13 and B14). WTF?

This kind of smashed my VGA-dreams :( , but on the upper hand it also made me curious :)

What the hell are these two pins used for?

Do they carry some digital signal or do they just "raise a flag", and what's the use?

[TheGZeus]

I believe they take calls from the software to determine these signals.


That's one of the reasons overclocking throws grapnics out of whack, the woftware is designed with a certain speed in mind, and now it's trying to draw a line when something else is in a blanking period...
There are ways around it, but not simple ones.

[KillerBean2]

I believe they take calls from the software to determine these signals.

Does this mean, that the actual Vsync and Hsync signals comes from the cartridge... or is it digital? Would it be useable for a VGA mod :?:

A Megadrive with VGA-out would be totally awesome :yum:

[Joe Redifer]

Good luck. VGA's minimum spec is 640x480.

[evildragon]

VGA must be 30KHz, TV is 15KHz..

Just because it has H Sync and V Sync doesn't mean it's VGA...

[KillerBean2]

Damn, that's right! I happily forgot about both of those obstacles, LOL :D

I gues an upscale converter like the XRGB3 would be the only way to go, if I want "real VGA" from my MegaDrive....

*sound of VGA-dreams being smashed with a sledgehammer*

[Elusive]

I want a brain-jack so I can plug my system directly into my optic nerve and get the purest signal possible.

edit: On second thought, better not. That's too Max Headroom for my tastes :P

[KillerBean2]

Good luck. VGA's minimum spec is 640x480.

I have been snooping around a bit now, and it seems it's not ecatly true.
My CTR monitor should be able to accept any resolution I throw at it.

Besides, how else would I be able to play Doom in 320×200 ;)


But Evildragon is still right about the problem with the horizontal refresh rate, so I've been thinking about building myself one of these suckers:

http://elm-chan.org/works/sc/report.html

...just leaving out the S-Video part of the circuit.

"Why all of this madness??", you might ask. Simply because my PC monitor way bigger than my TV set :D

[TheGZeus]

Doom is PROCESSED IN SOFTWARE at that resolution.
The actual output is full VGA spec. It's doubled pixels etc.
Think of the screen size adjustment (-+) as a ZOOM more than a shrink, and it might make more sense.
Or in a Genesis emu, running full screen.

15khz horizontal refresh=no work.

[KillerBean2]

Doom is PROCESSED IN SOFTWARE at that resolution.
The actual output is full VGA spec. It's doubled pixels etc.
Think of the screen size adjustment (-+) as a ZOOM more than a shrink, and it might make more sense.
Or in a Genesis emu, running full screen.

I gues, I have to build a scaler too then :D


15khz horizontal refresh=no work.

Did you even bother to look at the link, I just postede?

[TheGZeus]

No.

Why aren't you buying one again?

[KillerBean2]

Buy what? An upscale converter or a TV set?

I don't have room for a big TV set, and it's much more fun to build the converter yourself, even if it's completely nuts :D

EDIT: Just fixed a really stupid spelling error.