POLL: AVDP from texas

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By PingPong

Prophet (3448)

Аватар пользователя PingPong

03-09-2019, 11:10

time ago, TMS planned a successor of TMS VDP called the AVDP
https://www.datasheetarchive.com/pdf/download.php?id=710e005...
It's similar to V9938.
while not having all the features of Yamaha, it does have some interesting ones:
Table Driven 4x2 , screen 2 like mode (for reduced color spill, but patterned!)
Block Move
Ability to give direct access to host CPU ( kind of DMA mode )
10 sprites/scanline
HW scrolling (X/Y)

It never goes in production.
What do you think ? Would be a MSX2 based on this device instead of V9938 a better choice gaming wise ?

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By Parn

Champion (419)

Аватар пользователя Parn

03-09-2019, 15:59

It would have some interesting features, alright. I wonder how much better would 4x2 color limitation look compared to 8x1. Sprites seem similar to mode 2 sprites on V9938. They also would have made G1 more useful with 2 colors per pattern. I think this looks a bit more versatile than V9938 for action games (although games like Aleste would still look better on the V9938).

By Grauw

Ascended (8455)

Аватар пользователя Grauw

03-09-2019, 16:12

PingPong wrote:

10 sprites/scanline

The V9938 can display 8, but has the ability to specify a different colour for each line, and combining them into multicoloured sprites. So sure superficially 10 > 8, but whether it would actually be better really depends on the unspecified details. If it’s MSX1 sprites but just more of them, then I pass Smile.

PingPong wrote:

HW scrolling (X/Y)

Note that this most likely means a scroll of 8 pixels in the x/y direction, after which you need to offset the name table, just like how it works on the C64. The V9938 is already capable of that (in fact the V9938 can scroll 16 pixels). The horizontal scroll capability missing from the V9938 and added in the V9958 is a full-screen scroll for efficient use in the bitmap modes.

A better pattern mode for the V9938 would be nice. But screen 4 is also underutilised by developers and has a lot of untapped potential; e.g. I have yet to see someone make a multi layer scroll in it.

By PingPong

Prophet (3448)

Аватар пользователя PingPong

03-09-2019, 16:22

The Per scanline color is also in this texas VDP, the only thing is the OR color feature.
But on the other hand, you got even an interesting collision detection feature based on some attribute bits in the sprite.

By Parn

Champion (419)

Аватар пользователя Parn

03-09-2019, 16:49

Grauw wrote:

If it’s MSX1 sprites but just more of them, then I pass Smile.

They are like MSX2 sprites, but they don't mention any logic operations between two sprites.

Grauw wrote:

Note that this most likely means a scroll of 8 pixels in the x/y direction, after which you need to offset the name table, just like how it works on the C64.

The product preview mentions two separate scroll registers, one for each coordinate. It doesn't elaborate on how they work, but maybe it would scroll more than 8 or 16 pixels if it needed a full register for each coordinate?

By PingPong

Prophet (3448)

Аватар пользователя PingPong

03-09-2019, 17:54

if it was done by Karl Guttag only one register would be used to save transistors, because 8 px offset take 3 bits. So only a 8 bit register could be used.
the evidence that there are two registers means probably the luxury of a full 256 positions. (What a waste! MY GOD! i can hear Karl Guttag cry hard on this waste)

By PingPong

Prophet (3448)

Аватар пользователя PingPong

03-09-2019, 17:53

Maybe someone could find around there a more useful info that i've found. Someone had ?

By Grauw

Ascended (8455)

Аватар пользователя Grauw

03-09-2019, 18:08

Bitmap vertical resolution is 210 lines, pattern resolution 192 lines. What is this obsession with giant vertical borders.

Without OR colours you need more sprites, so I think two more isn’t really better. The 16-colour characters I use in my RPG would be difficult on this chip. Hardware sprite collision is generally not very useful, so that’s not a good trade.

Interesting document nevertheless Smile. I wonder when this AVDP was being designed. Before or after they got wind of Yamaha developing the V9938 and the SMS VDP.

By jltursan

Prophet (2180)

Аватар пользователя jltursan

03-09-2019, 19:07

I also prefer the V9938 sprites, the scanline color combined with the OR feature make them really powerful when wisely used. Nevertheless, the AVDP has that 128x105 full color resolution that could render some nice blocky games...

By PingPong

Prophet (3448)

Аватар пользователя PingPong

03-09-2019, 19:45

the question is: was texas that copied from yamaha or the reverse?
would be fine if one could find more info about this chip

about sprite / scan line: i always wanted a minimum of 12 sprites / scanline so this chip is more near to my whishes.
Let's look at rastan saga: with a 10/12 sprites / scanline the game could get wide and colorful sprites.

By jltursan

Prophet (2180)

Аватар пользователя jltursan

04-09-2019, 10:04

And thinking out loud, ¿can it be recreated with a FPGA?, ¿or maybe software emulated?

It could be fun to try to fill the gaps "recreating" a non existent hardware Big smile

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