Standard VDP and VDPX output will not be mixed at all. Why would you anyways as VDPX already supports up to 8 layers and 128 simultanious sprites.

Original MSX output is routed from the SCART into the VDPX cartridge. VDPX is going to offer a VGA connector and a composite video output. With a register bit you can switch between VDPX and standard VDP, it simply flips an analog video switch.

This means that you can use an MSX monitor or a VGA monitor/LCD with VDPX and you will not need a second monitor whatsoever.

Normal VDP output will not be sent to the VGA connector though, only to the composite video out of VDPX.

Thus, you can use one monitor, or two if you so prefer.

so an LCD that autodetects signal and auto-change from COMPOSITE INPUT to VGA input and viceversa will rules!

The only one way to allow that is that VDPX turn off the sync signals when composite out is selected for showing v99x8. do you already thinked that?

Composite video output is crap ... Both for hires and color issues.
It would be better to offer an more upscale video output (S-Video or RGB).

With such an amount of connectivity it's better to build a separate videobox for VDPX. Then there will be room for two SCART connectors as well (MSX input, VDPX/MSX output). Then VDPX would only have the VGA port which could directly connect to a VGA screen or, to the the videobox.

There's no way I can house a ton of connectors and video protocols onto the bare cartridge.

again, why not only one RGB/VGA OUT and the only one output.... the same RGB type connector than any MSX2?

the only one problem is: how to bypass the vdp's msx2 image to the RGB OUT....

again my idea is to read the image from the RGB out of MSX2, saving the image in some little RAM to save the current frame, and to reads from that RAM outputing to the output (a doubler do that IIRC).

you needs only one out & only one input.

You are speaking of a digitizer and that's not what I'm going to add to VDPX. At least not in it's current form. All it will do is to route the analog MSX output to VDPX output if VDPX is told to switch to MSX output. A minimum of 3 connectors is required. Scart IN, Scart OUT and VGA OUT.

Digitizing video input only make the design unnecessarily more complicated and expensive. Another concern is the cartridge itself. With some MSX'es it goes vertically into a topslot, or from the back, horizontally and with yet another model into the front side, also horizontally. The cartridge itself needs to stay compact; two scart connectors don't fit next to each other with the standard width of a cart. That is why I initially would go with composite video.

Since RGB connectivity is desired I'll come up with an extension module that provides all the IN/OUT connectors. A module that's controlled by VDPX. That way you can have a neat cartridge with only one cable going from it to the IN/OUT module which you can place behind the MSX.