Screen 7 vs Screen 8... a retrospective

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By snatchertas

Supporter (10)

Аватар пользователя snatchertas

02-04-2018, 13:30

Hello everyone! I was recently going through the MSX2, 2+ and TR games library and a question formed in my mind:
There are many more games in Screen 7 than anyone would expect and hardly any Screen 8 games. Why is that so? I started considering the various possible reasons but it still baffles me.

This is what I came up with and I would like to hear your opinions on the matter:

We all know that Screen5 is the king of MSX2 since you get 4 pages (1 active plus 3 more) of 16 color graphics from a Color Look Up Table (CLUT). This way you can have 2 pages to swap plus 2 more pages to fill up with graphics data. This way even 64kb MSX2 machines could make full use of the available memory. Cool!

Now, Screen 7 is the same as screen 5 but you sacrifice 2 pages for double the horizontal resolution. Now you get 1 active and one extra page. However swapping pages is now a problem as you won't have anywhere to store the graphics data (standard ram excluded). What you are left with is not using page swapping and live-updating the active page with graphics data that is stored on the second page. This is not an ideal way to draw your game graphics but it can be done with certain restrictions. Sprites are drawn with half the resolution and they use the same CLUT as the rest of the Screen. Fading in is possible since a CLUT is used so drawing a screen with all colors set to black and then fading in can be a helpful trick.

Then we move to Screen 8. Now you get the standard resolution, 256 non CLUT colors and, just like Screen 7, 2 pages. You get 16 color hardware sprites that are locked in the standard MSX1 palette.

Now, from a certain point in time you could see that Screen 7 became the prevalent screen mode in MSX2,+,R games. However with the 2 page restriction you would expect that many would opt for more colors rather than double the resolution (considering the lame video quality of the CRT TVs).

Here are some reasons for the Japanese developers opting for Screen 7 that I could think of:
1) As the MSX started to show it's age, action gamers left the platform. The latest games are not action oriented but rather strategy, RPG and adventure type games that heavily feature Kanji characters. This would be a very good reason to opt for the higher resolution.
2) As the MSX standard stopped being the market leader that it once was (in the low price point segment of Japan) games started being cross-developed or ported from the PC-88 line of computers. This is really obvious as there are numerous games that use Screen 7 with a horrible static pallet. Case in point, Snatcher on MSX2 uses 100% PC-88 artwork.
3) The latest games heavily feature manga style artwork. Since this style uses few colors and black outlines, it makes sense that it would be better represented in a higher resolution rather than a with more colors.

As a point against Screen 8 I would add the static pallet of the sprites that would severely limit hardware sprite use and more or less force developers to use "software" sprites.

Another point against Screen 8 is the inability to do Fade-ins, Fade-outs and color circling. But this is hardly a deal-breaker in my opinion.

However, 256 colors at once, used in such a straightforward way was a HUGE differentiator of the V9938, back in the day, and one would expect that it would be used far more than it did.

In Europe there were "Goody" and "Dr Livingstone" from Opera soft as well as "Breaker" that proved the viability of Screen 8 games, but the Japanese did not agree (apart from Ikari, early on and a few RPG from little known companies).

As new games appear on MSX with the resurgence of retro-developing I would really hope to see new developers taking advantage of screen 8 and restoring it to it's rightful position in history, as a graphics mode that was 10 years before it's time!

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By Manuel

Ascended (17747)

Аватар пользователя Manuel

02-04-2018, 14:28

Artrag did some nice tech demos in screen 8.

By Grauw

Ascended (9737)

Аватар пользователя Grauw

02-04-2018, 14:32

Another reason screen 7 and 8 were not used as often is because the screen data is twice as large as screen 5, so the high-speed VDP commands take twice as long (others are the same speed).

For screen 8 the static sprite palette is indeed a problem, although it’s not the MSX1 palette but a different (uglier) one.

By PingPong

Prophet (3680)

Аватар пользователя PingPong

02-04-2018, 14:37

of course the screen 8 have some extra kind of disadvantages (as you mentioned) over screen 7 but
the real problem was that screen 7 & screen 8 required a massive amount of vram.
To make some games able to benefit of screen 7/8 features they needed a FAST vdp.
V9938 is severely lacking speed. it barely can manage screen 5 amount of vram and often the speed is not adeguate.
most of the time the z80 @3.5Mhz had to wait for small commands to complete.
To achieve a good speed the v9938 should had:
- Faster blitter (at least 5 times faster, with a lot of inefficiencies removed from the original vdp engine-state machine to gain speed)
- A kind of true DMA, stopping the CPU and performing memory exchange/move between ram/vram in a faster way to compensate the lack of vram size with the use of standard ram if needed.

With those improvements, even screen 8 action games could be achieved.
About hw sprites: they are needed on low power machines and are a limited solution in the absence of fast blitter or cpu that are able to manage sw ones. they are too limited in color and size to be comparable with the beauty of screen 8.

By DarkSchneider

Paladin (941)

Аватар пользователя DarkSchneider

02-04-2018, 17:28

SC8 was really intended for pure imaging, so it has a let's say good 256 color palette for bitmap, and not-so-good 16 fixed palette for sprites, but for OSD content (sprites over the bitmap) that is not a problem really.

SC7 was intended for editor or multi-layout applications. You can fit more info with hi-res, and have 80 columns text combined with graphics (like the publisher app does).

Think they were not intended for games in any case, but maybe for some kind of non-moving games like adventures.

By snatchertas

Supporter (10)

Аватар пользователя snatchertas

03-04-2018, 08:30

Still, Screen 7 has been overwhelmingly more supported by developers than Screen8. As there is no memory advantage in using screen7 rather than 8, I still believe that there could be dozens more Screen8 games. Alas, this wasn't the case and our MSX2 got sloppy 16color (or even 8 color) ports of PC-88 games rather than what could have been an amazing collection of never before (or elsewhere) seen 256 color marvels Sad

By Grauw

Ascended (9737)

Аватар пользователя Grauw

03-04-2018, 09:11

I wonder why the screen 8 sprite colours limitation is there. Screen 10-12 don’t have it, and from my pov the V9958 was only a minor upgrade, so it couldn’t have been hard to implement (my feeling about most V9958 features, and it lacks a CE interrupt still). Though I guess they did touch on the colour processing / palette architecture for those screen modes, so maybe it was an area they were changing anyway (but then failed to expose the 15-bit RGB DAC to the palette Crying).

By Manel46

Hero (621)

Аватар пользователя Manel46

03-04-2018, 09:52

A good solution for sc7 / sc8, is the use of the HMMC and LMMC commands. This way you do not have to save anything in the VRAM


Enlighted (6497)

Аватар пользователя ARTRAG

03-04-2018, 09:56

Palette for sprites and vdp speed are limiting but not that much. This is screen 8 on plain msx2

I think that many screen 7 games are ported from other platforms with resolution similar to the screen 7 specifications
This is the real main reason why we has so many screen rpg

By snatchertas

Supporter (10)

Аватар пользователя snatchertas

03-04-2018, 10:18

A shame really. It would be a great differentiator in a time that even the Amiga could not handle that many colors in a remotely practical way.

However there are lots and lots of games that could shine in Screen 8. There were so many non-Japanese titles that were not heavy on scrolling and big sprites. For instance I believe MSX2 could make a gorgeous Rick Dangerous in screen8 even with software sprites. Let alone Dungeon Master style games that would take full advantage of the pallet by doing software color mixing etc

(I know there are lots of Japanese DM style games, and many of them are in Sc7 which proves that VRAM is enough for such a game)

By AxelStone

Prophet (2919)

Аватар пользователя AxelStone

03-04-2018, 16:52

I don't think that SC7 / 8 were designed to be game modes, they have limitations (speed, VRAM). You are going to waste too much CPU resources doing the graphical part and perhaps it's more interesting to design a better gameplay (more complex IAs, etc) to get a deeper game experience.

PErhaps they are nice options to do adventures with static screens, specially if you use massive storage device (HDD, flash memory) to get fastest load times.

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