I wonder how hard it would be to install a second V9938 or V9958 with its own VRAM and with the I/O ports at an alternate address. You could have the output multiplexed so that VDP2's video would be displayed when the output of VDP1's color bus was zero or something. Then you get two layers, twice as many sprites and colors and all that good stuff.

And how about running the color bus lines to the address lines of some SRAM, with the data bus of the SRAM going to a 15/16/18/24 bit video DAC. Then with some other logic the Z80 could write palette data to the SRAM. Instead of screen 8 being 256 fixed colors it could be 256 out of 32K (or more).

Think PC-Engine/TG16/SuperGrafx...

Yamaha V9938 and Yamaha V9958 in SLI/CrossFire... *droooool*

Can you use 256KB VRAM if you own 2 VDP's?
I was thinking in getting a MSX1 with 80 columns cartridge.

Maybe something more contemporaneous for MSX 2/2+?
The MSX project is supposed to work with a second VDP.

I remember seeing a modified MSX on some fair long ago, having 2 VDPs. The MSX ran some kind of multi-tasking OS and had one task (being MSX-DOS IIRC) running on one VDP/monitor and another taks (also MSX-DOS?) running on the second VDP/monitor ...

otoh, why would you need to build in a 2nd V99x8 if you can just plug in a Gfx9000

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otoh, why would you need to build in a 2nd V99x8 if you can just plug in a Gfx9000

How much would this cost? Any new benefit !?

Well, I wanted to know how their managed to get 256KB VRAM ...
Sure that 512 KB VRAM would be enough for some games!

I sometimes squeak about just this very thing though folks think I'm nuts (generally). Using multiple 9938/58 and/or 9990 overlaid for some truely arcade quality circa 80's or megadrive etc multi layer amusement. One issue strikes me though, as well as the actual availability of the chips which is going to sink with time is that wouldn't a cartridge containing these be legally classed as a "new product"? I seriously doubt these old ic's will be ROHS compliant. Someone with the knowledge have an idea if that's a problem or not?

I don't know much about ROHS (does USA even have some similar laws?) but these VDPs aren't being manufactured anymore right? If only existing chips could be used then who knows if it would be a problem?

I was just thinking about dual-VDPs as a possibility for the hobbiest who may have a spare VDP in her scrap pile that could be put to some use. Sadly, my scrap pile is limitted to PC stuff. Of course, GFX9000 is nice but those don't grow on trees either.

What is ROHS?

I remeber that i ones talked to someone ho's sayed that it is posible but need new faster vram
dual layer on a msx2 by 2 vdp's is cool
sli is the thing

Faster VRAM is only necessary when both chips read from the same memory, not if they both have their own. Which would be preferable because dual layer on 128K would be a bit tight.

"The Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment Regulations" ROHS stems from"Waste Electrical and Electronic Equipment" which is all about environmentally responsible disposal of the technology after it's no longer "of use" and prohibits the use of particular materials in manufacturing. It's EU reg stuff, if you manufacture/sell electronics it's something you have to deal with from this year onwards. The regulations don't apply to the US obviously but it seems that US manufacturers take it seriously, after all they wouldn't be able to sell their parts in Europe. No doubt there's plenty of EPA rules in this style in the US but I'm not in the US

I would assume it to be "reasonable" for a hobby peep to knock stuff out without worrying too much, but you can never tell with these nuts making all the rules, it could be argued that this is an act of recycling.. maybe, but if one was to make OldVdp Co and sell these parts as some kind of commercial enterprise there could be some "issues". Of course, the vdp's are so old and are simply unavailable new but they could turn around and suggest this is a reason to redesign your hardware.

I guess it's a traditional case of just trying to stay off the radar and hope nobody notices
But I still want some multivdp carts with multi layers

Great, thanks for the explanation, boblet!

Does anybody remember the "Goblin/Twin VDP" Japanese device?. I remember it was introduced at some meeting in Japan. It featured an extra VDP, image mixing with the existing one, dualplane...

Really? I've never heard about this Goblin/Twin VDP device... does anyone have more information about it?

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Really? I've never heard about this Goblin/Twin VDP device... does anyone have more information about it?

With some googling , I found www.nodus.ne.jp/~ghost/msx/emsxnews_old.htm
If this is truth, and it's still available.