V9990 is not part of MSX

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By Grauw

Ascended (10560)

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17-01-2022, 22:11

gdx wrote:
Grauw wrote:

I’d like a real V9990 with superimpose honestly… It was planned for the KrakenGraph Full version, but I haven’t heard any recent updates on it.

I think it's hard to get an image of quality for a reasonable price with superimpose.

Why, though? To my understanding, superimpose is pretty simple:

1. Feed external HSYNC / VSYNC into V9990 HRESET / VRESET pins for synchronisation
2. Combine external and internal R, G, B with an analog multiplexer, controlled by /Ys signal

I’m sure there’s complications I’m missing, but since the principle is that the original external signal is passed through while /Ys is not superimposing, the quality of the signal should not suffer.

By gdx

Enlighted (5338)

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18-01-2022, 02:00

I said that because most devices I've seen degrade the image. Only very few reproduce an image with almost no degradation. They have lots of components and were expensive. I have never seen a simple and cheap device with a faithful image.

By madscient

Master (193)

madscient's picture

18-01-2022, 04:14

Most superimpose functions combine the video composite signal. This is why the quality appears degraded.
As Grauw says, the degradation would be less noticeable with a method of superimposing the RGB component signal and encoding the combined video to composite (if necessary).
However, in that case, of course, three superimpose circuits are needed for each three signals R/G/B.
This is one of the reasons why they are expensive.

By iamweasel2

Paladin (701)

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27-01-2022, 03:20

Grauw wrote:

If you want to superimpose the V9990 behind the V9938, just use a Philips NMS8280, Sanyo MPC-27, Sony HB-F900, Sony HB-G900, Victor HC-90, Victor HC-95, National FS-5500, Daewoo CPC-400S, etc.

Will that approach work on openMSX as well? I don't have any of these machines, so I could only test it on openMSX.

By Manuel

Ascended (18705)

Manuel's picture

27-01-2022, 07:58

No, openMSX currently doesn't implement the superimpose of these machines.

By edoz

Prophet (2437)

edoz's picture

27-01-2022, 15:40

Manuel wrote:

No, openMSX currently doesn't implement the superimpose of these machines.

Still.. it is the best emulator for sure!!

By Grauw

Ascended (10560)

Grauw's picture

27-01-2022, 23:36

Manuel wrote:

No, openMSX currently doesn't implement the superimpose of these machines.

Doesn't it for LaserDisc systems? Although probably not in a way flexible enough to allow selection of alternative video sources like the V9990...

That said, I doubt how useful it would really be. Superimposing the V9990 on top of V99x8 like Video9000 does makes more sense to me. But maybe having the option, if all it takes is adding some configuration commands, could be nice. Generalizing the code may also be nice for the code base.

By Manuel

Ascended (18705)

Manuel's picture

28-01-2022, 00:01

Wouter told me the other day that there seems to be superimpose code in the video 9000 emulation... Perhaps someone can just try it out.

By Pokun

Rookie (31)

Pokun's picture

06-02-2022, 21:48

That the V9990 served as a basis for the Super Famicom's S-PPU was news to me. Nobody knows more about this? I haven't looked into the V9990 much, but I'm familiar with the S-PPU and it is a fantastic video chip so I suppose the V9990 is also fantastic.

By Pentarou

Champion (416)

Pentarou's picture

06-02-2022, 23:10

Maybe Nishi had a brain fart and confused the SFC with the MD.
As far as everybody knows the SFC chips were made by Ricoh, while Yamaha did the MD chipset.

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