Here there is preliminary pag. 50-51 only:

http://download.ic37.com/pdfold5963lkuifg/2005-8-9/5056/V9978_www.ic37.com.pdf

Someone told me that v9978 is v9958+v9990, but honestly
I suspect the v9978 never been existed as a this VDP. Probably the v9990 IS the v9978 renamed, without the v9958 core.

However,it's good to have the rest of the datasheet scanned...

V9978 is the successor to the V9958, but they cancelled the project and turned it into a V9990 instead. This was explained in one of those new MSX magazines. So, probably the V9978 doesn't exist in reality, but maybe they had already written the datasheet?

Everything looks very much like v9990 except one very cool thing: it offers direct CPU access to VRAM via a 16-bit bus!

Quote:

Everything looks very much like v9990 except one very cool thing: it offers direct CPU access to VRAM via a 16-bit bus!

@Manuel: ? where you found that information? (the 16 bit vram access ).

Quote:

Quote: Everything looks very much like v9990 except one very cool thing: it offers direct CPU access to VRAM via a 16-bit bus! @Manuel: ? where you found that information? (the 16 bit vram access ).

Please ignore my prev. post.

Holy cr@p! So THIS is what the turbo-r's were meant to have as a VDP?
If that happened, maybe - just maybe, it wouldnt be so short lived as it was...

Manuel : The v9990 has this feature too

Quote:

Holy cr@p! So THIS is what the turbo-r's were meant to have as a VDP? If that happened, maybe - just maybe, it wouldnt be so short lived as it was...

Yes, If. If. If. If.

If the msx1 vdp was not sooo crappy the msx could have been a better life and diffusion. IF.....

msd: ah, so, so far no differences with V9990?
It's a pity that this 16-bit bus is not used on the MSX version of V9990 then...

The page does not list explicit V9958 compatibility modes, right?

Based on these specs, it seems the use of V9978 on turbo R would be similar to R800. This means it would use V9978 as main video chip and a V9958 to compatibility. Of course, as everything said, this is just speculation. Maybe V9978 would have V9958 compatibility (E-VDP III means something, related to E-VDP II and E-VDP I) but it was never finished and that was (one of) the reason(s) why Yamaha changed the chip name to V9990 (compatibility modes existing on V9990 could be just the unfinished support to a V9958 compatibility mode).

Quote:

msd: ah, so, so far no differences with V9990? It's a pity that this 16-bit bus is not used on the MSX version of V9990 then... The page does not list explicit V9958 compatibility modes, right?

The MSX only has an 8 bit data bus, so unless the V9990 has support for byte writing, adding direcht VRAM access to the graphics 9000 is likely to be more trouble than it's worth.
Does the V9990 need to support byte writing? I don't think so; vdp commands can be used instead to set pixels, and for larger changes having a 16 bit bus is an advantage.

Hmm, these 2 pages are practically identical to the first 3 pages of the V9990 Application Manual (E-VDP-III ;-)

arnold_m.. yes it supports byte writing...