New game convertions!

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Por LeandroCorreia

Paladin (955)

imagem de LeandroCorreia

28-11-2007, 20:41

Do these games run faster in the Spectrum, if so, is it because of bad conversions?

And in case of bad conversions, wouldn´t be easier/better to convert them directly from their Spectrum ports?

Por ARTRAG

Enlighted (6845)

imagem de ARTRAG

28-11-2007, 20:58

Do these games run faster in the Spectrum, if so, is it because of bad conversions?

And in case of bad conversions, wouldn't be easier/better to convert them directly from their Spectrum ports?

Not so sure, very often, due to the HW differences, the "bad" conversion has no alternative.

Generally speaking, conversion of Speccy games that minimize the VRAM accesses (e.g. only one sequential RAM->VRAM) work fine.
In this case the strategy is: leave the Speccy code work in RAM and at each frame dump it on the tiles in VRAM.
If the Speccy code was light, even with this overhead, the game works fine also in MSX.
If the Speccy code was heavy, the (unavoidable) overhead results in a slow and frustrating game.

Anyway BAD conversions exist. Bad conversions translate each access to the RAM that the ZX used as VRAM to
an ACTUAL VRAM ACCESS!! This results 99% of the times in crappy games, as everyone can easily imagine.
Reading and writing from VRAM to set a mask of bits is the worst thing to do on MSX and takes ages compared to the
direct LD instructions of z80.

Por spl

Paragon (1470)

imagem de spl

28-11-2007, 21:38

ARTRAG, I have here a good disk conversion of WEC LE MANS which was done as far as I know by Martos near 3 years ago. It features the loading screen and in a simple MSX 2 works very good Smile. The problem is that I haven't been able to run it from DOS-2 - BASIC 2.X

Por SLotman

Paragon (1240)

imagem de SLotman

28-11-2007, 23:00

spl: thanks for that list, it will help a lot!

There is a convertion of Wec LeMans that works from DOS2, even on my turboR - made by Martos! It runs great with turbo Smile

I also clearly remember playing Dragon Ninja to the end... must test it again, and if all versions do hang, I'll dig my old disk here Smile

The thing with Spectrum convertions being slower, in most of cases is due to VDP access on MSX being tons of times slower than on Spectrum - it isnt the programmers fault!

99% of convertions uses a framebuffer where it draws everything on RAM - then it makes just one HUGE RAM->VRAM transfer. This on Spectrum is VERY fast, since you get direct access to VRAM (ADVRAM anyone? Smile ) - on MSX, it is much slower.

So for a convertion to run at full speed, on MSX1 without turbo - the game would have to be completly rewritten - (to use sprites, minimize screen rewrites, etc) and in some cases it wouldn't be possible at all!

Some games (like Time Scanner and Alteread Beast) try to output data as fast as possible to VRAM - but then, on some MSX1s this would cause garbage on screen... so in this case, for the game to be better adapted, you have to slow some things down *even more*!

Also on Spectrum, the video mode is linear - so writing on VRAM 8 bytes would fill from 0,0 -> 7,0; on MSX writing 8 bytes to VRAM will fill from 0,0 -> 0,7; so extra coding is necessary on this when converting the game...

There are several architeture differences between MSX and Spectrum which makes the game "ported" slower on MSX by default. I'm not saying that Spectrum is superior to MSX - but in VRAM access speed, Spectrum wins, hands down. Now who has the better image quality, Spectrum can't touch the MSX Smile

Por LeandroCorreia

Paladin (955)

imagem de LeandroCorreia

29-11-2007, 00:00

Thanks for the answers, guys...

Or to put it simple, the price of the better image quality of the MSX is its slower speed. Wink

Por PingPong

Prophet (3898)

imagem de PingPong

29-11-2007, 00:57


Not so sure, very often, due to the HW differences, the "bad" conversion has no alternative.

As said by Artrag, most of the times a direct emulated conversion is not the best thing.
zx does not have pattern modes like in msx1. this means that on zx programmers are forced to scroll the screen via brute force, moving 6144 bytes of screen every scroll. this could be done because zx have vram directly accesible from cpu and we can use ldir for example. This approach is often unpraticable on msx due to the slowness of otir, combined with the vdp inability to keep at those speed.

However, as often happens, using specific features of the hw is the best choice. msx does have patternizzed mode that used correctly helps a lot. take into consideration the gng demo by dvik. He showed what is possible to do with pattern mode.

Most of the zx spectrum games could be re made using this approach and of course moving only 768 bytes instead of 6144 can compensate for the slow vram access...Wink

Por MäSäXi

Paragon (1884)

imagem de MäSäXi

29-11-2007, 10:30

ARTRAG, I have here a good disk conversion of WEC LE MANS which was done as far as I know by Martos near 3 years ago. It features the loading screen and in a simple MSX 2 works very good Smile. The problem is that I haven't been able to run it from DOS-2 - BASIC 2.X

I bought Wec Le Mans in the 1980s, and I don´t remember it has loading screen.... unless you mean simple screen 1 or screen 0 message:

WEC LE MANS IS LOADING

PLEASE WAIT

(or something like that)

and I think that text was in a box made of characters taken from MSX ROM.

So your loading screen must be taken from spectrum original which didn´t exist on msx.... Sad "very good" spectrum-->msx conversion indeed... like too many msx games....

Por ARTRAG

Enlighted (6845)

imagem de ARTRAG

29-11-2007, 11:41

WEC LE MANS has the best 3D simulation of the landscape I've never seen
in any msx racing game.
Rising and descending hills is smooth and realistic, where the horizon line
moves accordingly to the distance of the hills that hide threes and mountains.

Por LeandroCorreia

Paladin (955)

imagem de LeandroCorreia

29-11-2007, 12:55

I´d say the same about Wec Le Mans, by far the best racing engine for the MSX. Life in the Fast Lane is cool too, too bad this game sucks. And please, let´s not talk about MSX OutRu(i)n(ned). Tongue

The interesting part in creating a terrain with hills like that is the fact you just need a very single amount of extra processing and memory. However, to put masked objects into the scenery, well, that would be something completely different. Wink

Por NYYRIKKI

Enlighted (5939)

imagem de NYYRIKKI

29-11-2007, 13:28

How come I don't remember anything good about Wec Le Mans? Maybe I should check it out again...

Only thing that I really remember about that game was article in local magazine titled "Wec Le Mans... ainakin mun koneesta" that did not give a very good impression of the game.

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