Author
| Yamaha V9978 Datasheet!
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KdL
msx user
Posts: 59 |  Posted: April 17 2008, 02:11 |
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PingPong
msx professional
Posts: 840 | Posted: April 17 2008, 09:04 |
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.
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PingPong
msx professional
Posts: 840 | Posted: April 17 2008, 09:05 |
However,it's good to have the rest of the datasheet scanned...
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manuel
msx guru
Posts: 3347 | Posted: April 17 2008, 12:54 |
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!
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PingPong
msx professional
Posts: 840 | Posted: April 17 2008, 13:54 |
Quote:
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Everything looks very much like v9990 except one very cool thing: it offers direct CPU access to VRAM via a 16-bit bus!
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@Manuel: ? where you found that information? (the 16 bit vram access ).
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PingPong
msx professional
Posts: 840 | Posted: April 17 2008, 13:59 |
Quote:
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Everything looks very much like v9990 except one very cool thing: it offers direct CPU access to VRAM via a 16-bit bus!
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@Manuel: ? where you found that information? (the 16 bit vram access ).
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Please ignore my prev. post. |
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SLotman
msx professional
Posts: 514 | Posted: April 17 2008, 18:31 |
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... |
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msd
msx professional
Posts: 599 | Posted: April 17 2008, 19:51 |
Manuel : The v9990 has this feature too
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PingPong
msx professional
Posts: 840 | Posted: April 17 2008, 20:17 |
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...
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Yes, If. If. If. If.
If the msx1 vdp was not sooo crappy the msx could have been a better life and diffusion. IF.....
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manuel
msx guru
Posts: 3347 | Posted: April 18 2008, 08:51 |
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?
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Fudeba
msx lover
Posts: 69 | Posted: April 18 2008, 15:53 |
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).
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arnold_m
msx lover
Posts: 80 | Posted: April 18 2008, 20:03 |
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?
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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. |
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manuel
msx guru
Posts: 3347 | Posted: April 18 2008, 20:30 |
Hmm, these 2 pages are practically identical to the first 3 pages of the V9990 Application Manual (E-VDP-III ;-)
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msd
msx professional
Posts: 599 | Posted: April 18 2008, 22:25 |
arnold_m.. yes it supports byte writing...
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