SMS VDP data transfer bandwidth duing vblank

Discussion of development of software for any "obsolete" computer or video game system. See the WSdev wiki and ObscureDev wiki for more information on certain platforms.
tomaitheous
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SMS VDP data transfer bandwidth duing vblank

Post by tomaitheous »

Given a frame of 192 displayable scanlines on the master system, leaving 70 for vblank, what's the total number of bytes the z80 can write to the VDP? And what method does it use? I've seen the number of ~900bytes being throw around, but I thought TmEE said it could be higher than that.
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Re: SMS VDP data transfer bandwidth duing vblank

Post by TmEE »

Code: Select all

* 342 pixels per line
* 313 lines in PAL
* 262 lines in NTSC

* 1 slot every 4 pixels
* 1 slot every 2 on MD, with refresh cycles every 64 pixels
* 85 slots per passive line
* 10 slots per active line

* 228 CPU cycles per line

* 53693175 / 5 / 262 / 342 / 2 = 59.92Hz 
* 53203424 / 5 / 313 / 342 / 2 = 49.70Hz

* Tile is 32 bytes


Number of bytes that can be transferred using Z80 (OUTI):
+------+--------+---------+-------+
| Mode | Active | Passive | Total |
+------+--------+---------+-------+
| PAL  |  1920  |   1724  |  3644 |
| NTSC |  1920  |    997  |  2917 |
+------+--------+---------+-------+
Number of tiles that can be transferred using Z80 (OUTI):
+------+--------+---------+-------+
| Mode | Active | Passive | Total |
+------+--------+---------+-------+
| PAL  |   60   |    53   |  113  |
| NTSC |   60   |    31   |   91  |
+------+--------+---------+-------+
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Re: SMS VDP data transfer bandwidth duing vblank

Post by psycopathicteen »

Wow, that's convenient! All it needs is a block move!
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Re: SMS VDP data transfer bandwidth duing vblank

Post by tokumaru »

With a vblank bandwidth like that, I wish more Master System games would animate background patterns to create richer visuals... But most games stick to updating only the player's patterns. Some SMS games have really good background art when compared to the NES, because of the huge advantage of 4bpp tiles, but they tend to be mostly static, which kills the mood a bit. NES games with CHR-RAM also rarely animate backgrounds, but many CHR-ROM games do it, and it makes them look more advanced. If more SMS games had such animations, some could even pass for 16-bit titles.
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Re: SMS VDP data transfer bandwidth duing vblank

Post by TmEE »

You didn't really see animating BG tiles even on PCE where you have no VRAM access limits at all, or on MD or SNES which have fast DMA...
psycopathicteen wrote:Wow, that's convenient! All it needs is a block move!
There is OTIR and OTDR, but they are slower than blocks of OUTI or OUTD.
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Re: SMS VDP data transfer bandwidth duing vblank

Post by tokumaru »

TmEE wrote:You didn't really see animating BG tiles even on PCE where you have no VRAM access limits at all
The PCE is a completely obscure console around here, so I really haven't seen enough games to judge. At first glance, many PCE games look like SMS games to me: kinda like NES games, but more colorful.
or on MD or SNES which have fast DMA...
I can't think of many 16-bit games from the top of my head besides the Sonic games, which contain a decent amount of background animation: lava, parallax effects (not the kind created with scroll splits), spinning flowers, and many many more. My general impression of 16-bit games is that the backgrounds are more full of life than in earlier platforms. Palette cycling is often a part of it, but I'm sure that many update patterns as well.
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Re: SMS VDP data transfer bandwidth duing vblank

Post by tomaitheous »

tokumaru wrote: The PCE is a completely obscure console around here, so I really haven't seen enough games to judge. At first glance, many PCE games look like SMS games to me: kinda like NES games, but more colorful.
Besides obscurity outside of Japan, it's also pretty expensive to collect for. Yeah, that aside, there's emulation. You don't use emulation?

PCE is one of those rare instances where the addon became the main system about halfway through its life span. If you only play Hucard games, you only get a glimpse at early titles - the evolution of games finish taking place on the CD medium. PCE = hucard and CD games. Some early games strattle that 8bit-16bit genre/design. Some devs treated it as 'nes with extra features', as Chris Covell would phrase it, so the range of game design runs the gamut on the system - more so any MD or SNES (competing systems of the era). A lot of PCE games have more of an early 16bit feel, than an 8bit feel. But I wouldn't call it SMS like. Except for some late gen SMS games, SMS games are pretty 8bit in design and feel. Some late gen SMS games, like some late gen NES games, feel closer to early 16bit stuff (or SNES games, minus the fancy graphics. SNES games in general don't put a lot of enemies on screen at once. SNES has pretty colors, and but isn't a very 'fluid' system of the era. MD reigns in that department, with PCE seconded, snes last). Dracula X on PCE has like 3 times the amount of animation compared to the SNES 'version'. Nothing on SMS comes close to Street Fighter 2 'CE on the PCE hucard, let alone the Neo Geo fighting ports to the PCE CD. Top tier SMS games are no where close to top tier PCE games. Top tier SMS games don't even equate mid tier stuff on the PCE.

Some early hucards that were popular (in the US released in '89-90):
Bloody Wolf
Ninja Spirit
Dungeon Explorer (5 players at the same time)
Splatter House
Legendary Axe
Legendary Axe II
Neutopia
Blazing Lazers
Rtype
Devil's Crush
Aero Blasters
Bravoman
Cyber Core
Psychosis
Military Madness
Side Arms Hyper Dyne
Space Harrier

^I wouldn't say any of those reminded me of SMS games when I was playing them. The didn't play like SMS games, or look like SMS games, to me.
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Re: SMS VDP data transfer bandwidth duing vblank

Post by tokumaru »

tomaitheous wrote:Besides obscurity outside of Japan, it's also pretty expensive to collect for. Yeah, that aside, there's emulation. You don't use emulation?
I did give PCE games a try, and although I didn't think they were bad, none caught my attention for more than a few minutes. I still think it's an interesting system, but I wasn't able to develop a personal connection with it like I did with SEGA's and Nintendo's 8 and 16-bit machines.
But I wouldn't call it SMS like.
Definitely not as a whole, it's just that during the limited experience I had with the system, many of the games felt to me like better looking Famicom games, which is something that can also be said about some SMS games. I know that the PCE is much more capable than the SMS, but I didn't see that power being used very often.
Except for some late gen SMS games, SMS games are pretty 8bit in design and feel.
True, but the late games are the ones that made an impression on me, so I can't help thinking about them first. Games like Astérix and the Great Rescue, Deep Duck Trouble, Chuck Rock II, Daffy Duck in Hollywood, Aladdin, Cheese Cat-Astrophe, Gunstar Heroes (this might be GG only, but still), Masters of Combat, and so on, are damn impressive for an 8-bit console, and definitely comparable to PCE titles.
Some late gen SMS games, like some late gen NES games, feel closer to early 16bit stuff (or SNES games, minus the fancy graphics.
Being an artist, graphics is the first thing I'm going to compare, so I find it kinda hard to consider NES games comparable to early 16-bit stuff, due to the extremely low color count. Some of the games that I personally feel that get close are Sword Master, Astyanax, Moon Crystal (mainly for the cutscenes and smooth animations) and Bucky O'Hare. There are probably others I couldn't think of right now.
Top tier SMS games are no where close to top tier PCE games.
Probably not.
Top tier SMS games don't even equate mid tier stuff on the PCE.
That I don't know. The PCE looks pretty cool, but from what I've seen, there are lots of questionable games, and games with uninteresting graphics. For a system with so many palettes, I find it surprising how hard it is to find PCE games with outstanding graphics... Most games I see look just OK, compared to a lot of incredible stuff you can find on Genesis and SNES, but not because of hardware restrictions, probably just lack of talented artists (and lack of third-party developers to add variety and raise the bar). The SMS also has trouble breaking that graphical threshold, because of both hardware and talent, but the final result is that I end up seeing some similarities between it and the PCE. Not a whole lot like they're equivalent in every way, but still somewhat similar depending on the games I'm looking at.
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Re: SMS VDP data transfer bandwidth duing vblank

Post by tomaitheous »

tokumaru wrote:
Some late gen SMS games, like some late gen NES games, feel closer to early 16bit stuff (or SNES games, minus the fancy graphics.
Being an artist, graphics is the first thing I'm going to compare, so I find it kinda hard to consider NES games comparable to early 16-bit stuff, due to the extremely low color count. Some of the games that I personally feel that get close are Sword Master, Astyanax, Moon Crystal (mainly for the cutscenes and smooth animations) and Bucky O'Hare. There are probably others I couldn't think of right now.
For me, it depends on the game genre. It could be graphics or it could be gameplay. SMB3 on the NES is a pretty advance game. I would put the complexity of the gameplay as part of the 16bit era. Gimmick on the NES feels and plays like a 16bit era game. Matter of fact, it kinda feels like devs took to take a step back in gameplay complexity in the 16bit era - instead focusing on simplistic interaction with larger sprites instead. So in that respect they have more in common with later gen 8bit games (NES here) - just larger sprites. At least on the SNES. Megadrive games seemed to always be pushing that boundary - pushing around way more sprites.
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Re: SMS VDP data transfer bandwidth duing vblank

Post by Gilbert »

Well, for those who says the PCE has uninteresting graphics comparing to the MD, judge for yourself.
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Re: SMS VDP data transfer bandwidth duing vblank

Post by tokumaru »

Note: this is getting highly off-topic!

Sure there are cases where the PCE compares favorably to the MD or the SNES (from a quick look at that page, I can say this is the case of Lords of Thunder and Raiden, for example), but that doesn't necessarily mean that the graphics are particularly groundbreaking on any of the platforms, or on the arcade originals even. A lot of games in that page are arcade ports, so there's not much originality there, it's often the port that's most faithful to the arcade original that wins the battle, and the PCE undoubtedly has decent enough video capabilities to pull off nice graphics, so it can usually compete against the MD and the SNES despite having a single background layer.

If you really want me to, I'll try and list some MD and SNES games I consider to have groundbreaking graphics (most games will probably be exclusive to a single console, meaning that the games were designed to take advantage of that specific hardware, instead of adjusted to fit), so you guys that know the PCE much better than I do could give me some examples of impressive pixel art on that console, that isn't based on games from other platforms.
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Re: SMS VDP data transfer bandwidth duing vblank

Post by tepples »

Stills make the PCE look better than it is because the biggest thing missing from the PCE graphically is parallax scrolling.
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Re: SMS VDP data transfer bandwidth duing vblank

Post by tokumaru »

Come on, wouldn't you say these look quite Master System like?

http://tg-16.com/comparisons/tatsujin_pce_2.png
http://tg-16.com/comparisons/aero_pce_4.png
http://tg-16.com/comparisons/aero_pce_12.png
http://tg-16.com/comparisons/tiger_pce_6.png
http://tg-16.com/comparisons/lair_pce_5.png
http://tg-16.com/comparisons/lair_pce_8.png
http://tg-16.com/comparisons/hellfire_pce_4.png
http://tg-16.com/comparisons/tb_pce_05.png
tepples wrote:Stills make the PCE look better than it is because the biggest thing missing from the PCE graphically is parallax scrolling.
That's true. To judge properly, we'd have to see the games in motion.
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Re: SMS VDP data transfer bandwidth duing vblank

Post by tomaitheous »

Lol! If you actually played those games, then you wouldn't think so. You know that Monster's Lair is also on the Genesis, and is a Sega system16 game (lair_pce_x images)? Tatsujin looks SMS-ish???

And the aero_pce_x pics? This game looks sms-ish to you? http://www.youtube.com/watch?v=LAjr4sJrhrs

PCE doesn't have a lot of top tier graphical games. Even when it came to RPGs, which don't require parallax. If I were to post pics showcasing graphics, it would only show what the system is capable, rather than what's representative of typical, average, or even top tier stuff on the system. You'd have to take the time to play through the library yourself (hucard and CD), and not spend just a few minutes with each game.

Image
Image
Image
Image
Image
Image
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Image
Stills make the PCE look better than it is because the biggest thing missing from the PCE graphically is parallax scrolling.
The biggest achilles heel of the system. So much so, they tried to fix the problem before the SFC came out with the PC-Engine SuperGrafx. But, original games didn't have to suffer from the lack of parallax as much as they did. With sprites, hsync scrolls, and dynamic tiles - most original dev'd games could have been more parallax capable than they were. It'll never be on the level of systems that have more than 1 BG layer, but it could have been more that what's the norm is for the system.
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Re: SMS VDP data transfer bandwidth duing vblank

Post by tepples »

Effects that the NES can do as well. MetalStorm is an exercise in dynamic tile basturmation, and later NES games like Vice: Project Doom, Bucky O'Hare, and The Curse of Possum Hollow show off hsync scrolls. The one thing PCE has over NES and SMS in this sense is more sprite overdraw.
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