find a new vdp for msx

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Por fzanoto

Master (190)

Imagen del fzanoto

25-04-2016, 17:26

for some time I'm looking for a new vdp for msx.
which would be more promising than the V9990 and who have worked to 31khz ??
-gameduino
-FT812 ftdi chip (800x600 and 1Mb vram internal)

You have someone excited to develop any software or game to a new vdp?

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Por spacemoai1973

Expert (96)

Imagen del spacemoai1973

25-04-2016, 17:50

Yes

Por Pencioner

Paladin (993)

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25-04-2016, 17:57

I'm curious whether Z80 will be enough to feed bigger amount of videodata to more powerful/capable VDP - while there's bottleneck at VDP now, it will surely move to the CPU/RAM if we have more powerful video chip. So the question is - how much promising VDP could be handled by the current CPU? So no fitting of unfittable would happen.

Por Daemos

Paragon (1672)

Imagen del Daemos

25-04-2016, 19:24

Unless the new videochip has a ton of RAM to which the CPU can precopy all the data first and only needs to give commands. A command execution complete interrupt in combination with multiple parralel command executions would take all the time out of the CPU's hands.

Por tvalenca

Paladin (728)

Imagen del tvalenca

25-04-2016, 20:03

I doubt that. MSX Archictecture is flexible enough to let us integrate modern devices, but to limited data throughput you would need A LOT of dedicated memory managed exclusively by some modern devices to work... and at the cost of incredibly long loading times.

Just an example: A bitmapped 800x600 screen with 256 simultaneous colors would need 480000 bytes to draw a single frame. that would mean 480000 OUTs per frame, "only" SEVENTEEN TIMES slower than SCREEN5. If you make it 15-bit colors like the V9990, you'd have to OUT 1440000 times, an entire HD floppy disk which by the way were never supported on MSX. Think on how much time you need to format a 720k disk on MSX than you can have an idea of how much time we need to fill VRAM. (ok, we have SCSI, IDE and SD card interfaces which are bigger and faster, but you know it's simply too much for just one MSX screen!)

And call me old-fashioned, but software sprites are so AMIGA to me... (I know there are a lot of them on MSX games, even MSX1 games) We keep insisting on them, and when the code are ready we lose interest on finish coding the game. Maybe that's why there are so few V9958 games.

And about 31kHz, there are plenty of different approaches to convert MSX-Like screen modes to HD screens such as VGA 31kHz and HDMI. I won't say nothing about this matter because I dislike having pea-sized pixels even on a 4 meters away 46-inch TV. Grain of sand-sized pixels are ok to me, so I am comfortable with old 4:3 and 5:4 15kHz capable 17 inch monitors (which I own two).

EDIT: Yay! 400th post!

Por flyguille

Prophet (3029)

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25-04-2016, 20:38

z80 at 3.57 is unable to use the 100% of v9958, my game demostrate just that, z80 is not fast enough for using actual vdp at 100% its possibilities.

So bigger vdp, means nothing.

But what can allow, a "better" vdp (not bigger), to add features like do easier parallax (two bitplanes for background with independent scrolling registers). Or others actual feature that does not do well.

By example, the actual vdp commands engine, don't do X/Y wrap, so it is wasted time in Z80, to check and divide the comand in halfs or quarters for allowing to overcome the X=256 or Y = 256 barrier. That is a huge overhead for z80 having to divide a command in halfs or quarters. If the vdp helps wrapping coordinates, the z80 can do 15%-20% faster!.

And this is not any exotic new feature, just doing the command engine smartly more helpful.

Por tvalenca

Paladin (728)

Imagen del tvalenca

25-04-2016, 20:42

@flyguille, I missed something: do your game, running either on 7MHz Z80 or R800, reach 100% or VDP utilization?

Por Pencioner

Paladin (993)

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25-04-2016, 20:46

IMO, better VDP should have an option to map VRAM pages to RAM address space, so no more a lot of I/O VRAM access which is way slower (i do understand that mapped VRAM could have been used by video renderer at the same time but i bet it would be faster anyway, and good software would take care of it and access VRAM in idle time slot)

Por flyguille

Prophet (3029)

Imagen del flyguille

25-04-2016, 21:05

tvalenca wrote:

@flyguille, I missed something: do your game, running either on 7MHz Z80 or R800, reach 100% or VDP utilization?

Yes, it do, but consider it do in its genre which is platform game. This kind of games uses an approach of "many characters/ independent elements" which must be handled independently in classes and that each element interact with the scene background, so it do a heavier use of the z80.

There exists light genres, by example street fight games, ex. two characters, which does masivelly bigger characters in screen, but very few code to run for the behaviour and other stuff. And is basically a genre which most of the time is doing massivelly blitting to the vdp.

There is intermediate genres, like shot'em up, where is many characters, but they don't interact with the background, and basically most of them follow hardcoded paths in screen. Saving a lot of code to run. This way allow to set up smothly on screen more characters.

Ofcourse don't count with games that uses hardware sprites only.

So, when the bigger problem, is the z80 speed, and if the same code is run in r800, it does so much more action, well, the obvious conclusion is z80 is not fast enough.

The strest test I did for my game show that fact.

You can't f* bigger ass whore with a tiny dick!. Wink

Por flyguille

Prophet (3029)

Imagen del flyguille

25-04-2016, 21:01

Pencioner wrote:

IMO, better VDP should have an option to map VRAM pages to RAM address space, so no more a lot of I/O VRAM access which is way slower (i do understand that mapped VRAM could have been used by video renderer at the same time but i bet it would be faster anyway, and good software would take care of it and access VRAM in idle time slot)

It is an old thought, from the spectrum / msx era, but as blitting is secuencial, I remember to see here experiments that prof that this is not an actual barrier.

Por spacemoai1973

Expert (96)

Imagen del spacemoai1973

25-04-2016, 21:08

You're game uses cpu for drawing so how can you say a faster vdp would be useless.!
A vdp with more vram and doing everything with blits should be your wet dream

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