MSX2 vs Sega SMS

If we push a bit further onto the MegaDrive realm and its VDP (again, an additional rework on the SMS one), my mind got BLOWN when I learnt (and realized) not that much ago that the MegaDrive VDP has JUST 64 KB's of VRAM. ALL the graphics of all the amazing Megadrive games we know fit inside its VRAM, again, 64 KB's... Of course, this VDP it has MANY other bells and whistles inside (double scroll layer + independant pixelwise scroll for them + extra stuff) and around (faster CPU/bus size/DMA, etc...) But if a similar VDP architecture as the megadrive one would have been used onto the MSX2, we could have had something similar to a "programmable PceEngine" (8 bit core + ACTUALLY powerful vdp).

We can say the core feature that pushed SEGA VDP's away (in a much better way than the V99X8 ones) was the "tile engine core" idea, just this: You define graphics using tiles and then you use these tiles for EVERYTHING ELSE: Sprites, Layer 1, Layer 2, etc... (megadrive).
If we speak about the SMS core, we get a similar idea: You define tiles, then you use them for sprites and for Layer 1 BG. (The SMS had only 16 KB's of VRAM, another fact that also blew my mind) .

Somewhat, screen 5, 6, 7 and 8 are a strange vision Yamaha engineers had, which is really powerful in theory, of course, but somewhat slow for heavy graphics blitting aground. I can't remember this video modes architecture being used in any other VDP I can remember from that era...

Besides, V99x8 blitting for games not using sprites (neither tiles) came as choppy and somewhat close to being unpleasant to play for me. As far as I can remember V99X8 blitting performance never came close to tile based VDP's. It allowed things that of course, tile based VDPs could have never dreamt of... But SEGA did the "right" thing in my opinion, with "just" a subtle evolution for the SMS VDP, and with an amazing additional one for the MegaDrive.

Greetings

PS: I got a real MegaDrive some months ago, and I'm amazed at the fact that the palette it uses is 100% the one from the V9938, it conveys the same colorspace than a good MSX-2 pushed game (Space Manbow for example). It's a pity the Megadrive VDP is inside a custom chip and is not as easily removable as the V99x8 ones... It would be a crazy idea trying to use a MSX 2/Turbo R (whatever) with a similar functionality chip as the Megadrive VDP, but mapped for the V99X8 pin layout/slot. I'm somewhat rambling now, but one can dream for free

I suppose the V9990 is probably closer to this "megadrive architecture" than any other V99x8 VDP released...

I was wondering something similar lately, while looking into the v9990 specs. On one hand there are the pattern modes. Basically converting screen 5 and screen 7 to tile modes, add more color, more sprites, layered scrolling. This is a move into the Sega direction. And I totally get it.

On the other hand there are even more bitmap modes. Why so many? And they even don't support sprites? Why did they put so much effort into this?

Anyway, on Youtube there's the Coding Secrets channel which has quite a few Genesis/Mega Drive videos. Quite interesting, and maybe inspiring for what a v9990 pattern mode can actually do.

You asked why a lot of bitmap modes, well, the explanation is simple:
hw sprites are a bad solution to the problem, that is because they are fast and require low cpu effort.
but they are Limited. For example, if you need a but not tall larger sprite object you need to waste a lot of hw sprites.
if you need some kind of color effect you are restricted to what the hw gives you otherwise no way.
With sw sprites you can trade fps for size for example, you can have a bigger sprite moving at 25fps while the rest is moving at full 60fps. hw sprites impose a limit on this flexibility.

Hw sprites were the solution when cpu power was limited and there where no blitter around.
But engineers realized that limitations and provided a better way to do things. Blitter support.

It is not by accident that even karl guttag, the father of tms who patented the hw sprite feature on TMS later moved on its successor to sw sprites .
It is not by accident that even if amiga provided hw sprites they are some what more limited and the engineer focused mainly on blitter. Because blitter does sw sprites better.

So V9990 does not surprise at all. Instead of wasting a lot of power giving support to hw sprites in bitmap modes they focused in give you all the power to the blitter and let you manage in the more flexible way that power.

It is for the same reason Yamaha introduced bitmap modes to the V9938 rather than focusing on tile modes as they did on the Sega VDPs: MSX was designed to be a machine for both business and games. Bitmap modes are more suited for business applications (GUI systems, digitising, DTP, etc.), so this was the design focus ASCII gave to Yamaha for the development of the chip.

Indeed this. The same could be seen on the MoonSound OPL4, everybody started to make PCM music, and its powerful 18 FM channels with many new waveforms and 4-op was pretty much forgotten.

On top of that, the native PSG of SMS is (strangely) also inferior to the one in every MSX machine.

In retrospective, that's really a shame. And yes, I am/was guilty of the same thing as well.