Converted from ZX Spectrum!

www.caetano.eng.br/MSXPage/gngoblins/?p=0&l=en

Great Work!

What's with this craze about converting ZX Spectrum games
Is it somewhat an easy task ?

Respectable effort from the converter but ugly games if you ask me !!

Who is the guy that convert ? Can i suggest to get all in monocromatic? the msx has twice the amount of vram to manage if we manage also attributes. Game speed should improve even on msx1

The Spectrum version was a fine version of G'n'G; but if the MSX version is going to trade speed for limited color I agree with PingPong and I best prefer a monochrome one (what's that "Static colors" feature?). Anyway, thanks for doing it!, maybe now a Green Beret conversion could be planned for a future, I think that's a far easy one than G'n'G.

Problem is that the 7 MHz CPU requirement is not that common. Right, people with a full fledged Turbo-R won't have any problem, but again, it is hard to accept that a monochrome game needs such a powerful CPU.

By the way, does it work smoothly on an MSX2+ with the high-clock enabled (that should be about 50% faster than a normal Z80)?

Aha!, much better with static colors option active!, now it plays almost as fast as the original version...

I'm a bit worried for this GnG port.
IMHO it could discourage other MSX developers to continue the work on the same game

http://karoshi.msxgamesbox.com/index.php?topic=613.0

Dvik's tests look by far more interesting than the ZX version...
Daniel ! do not give up on your project!

Seeing what you can do with a SPectrum port may also just encourage them to show what could be done with a native MSX version!

BTW
I've just tried the game and I have to say that it works well (in bluemsx with an msx2 emulation)
At least level 1 goes quite smoothly and the scroll isn't as jerky as I was expecting (I'm a "bit" prevented against ZX ports .
Even if not as nice as it could have been if developed for msx, it is worth a try.
Well done!

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Who is the guy that convert ? Can i suggest to get all in monocromatic? the msx has twice the amount of vram to manage if we manage also attributes. Game speed should improve even on msx1

This guy is Daniel Caetano, the one who made Knightmare Gold, who translated Snatcher, who made Shinobi disk version, amonsgt many, many other things.

And if you cared to try the game or read the info, you'll see that ther's already a "static color mode" - which was my suggestion to get a better "monochromatic" - the game for most of the part had the same color all over it, so why not set this color just when the stage begins?. It isnt "monochromatic", but the colors are written only once, at the beginning of each level. (Meaning, same speed as monochromatic, but with results closer to the original "color mode" than just b/w)

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Problem is that the 7 MHz CPU requirement is not that common. Right, people with a full fledged Turbo-R won't have any problem, but again, it is hard to accept that a monochrome game needs such a powerful CPU.

Actually, it's pretty common here in Brazil to have MSX2 or 2+ with 7mhz (made by Ademir Carchano); There was also hardware from Padial, and (afaik) several "7mhz kits" were also sold in Europe... Also people with A1WSX (besides the ones with turbo-Rs), or the OCM can benefit from it.

Before judging, see how fast the game is on Spectrum. 7Mhz is needed to be *that* fast. You can play the game (with frameskip and "static colors" on a MSX1, with pretty good results - just not *as smooth* as the original Spectrum version.

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I'm a bit worried for this GnG port. IMHO it could discourage other MSX developers to continue the work on the same game

You should be happy about having a new game. But if someone thinks something better than that can be done, then this should only motivate them to do it!

Seriously, all this negative feedback won't encourage Daniel to keep porting games... and he have at least more two (that I know of) that he wants to port... and already started one of them.

Apart from all that, he also gathered a lot of info on how to port games from Spectrum to MSX, which he is preparing to release later - so not only the guy port the game, as he will give the road map to everyone who whishes to do that too... let's at least be positive about this, ok?

Well, well, well... let's start again...

Metalion: why converting ZX games to MSX? First of all, my first MSX was MSX1 and most games were converted... Then I am somewhat fond of ZX Spectrum games. Also, converting games from Spectrum (GnG was my first full conversion) is not easy, but is exactly the kind of challenge I like to face. I was able to convert this game in about three weeks (about 1 or 2 hours a day of work) - not counting the time to gather all Spectrum information I needed - and two more months to add extra features (most time consuming was music, since the music compressor (PSG -> MPM - MPM being a new format that I'll release the specs soon) plus VRAM with Buffer replayer took me almost a month so I made it work flawless and with the minimum CPU requirements. I simply have no time to create a full-fledge game (nor the good will to cope with boring parts of game programming). Besides, I know several guys that like converted games (me included), so... it's just a matter of point of view.

PingPong: In slow computers (e.g. 3.57MHz) the game already runs in "monochrome" mode. The original version of "Static Colors" was plain black and white. But SLotman suggested that I could paint the screen with some colors when the stage starts and then forget the color paint... this has the same "overhead" as a black and white game, and the visual impact is less obvious (in some places, the game even looks like the "full colored" version... Er... I said full colored? Well, whatever it means on a Spectrum game.

jltursan: the conversion is not slower only because the colors, there are a lot of problems involved, like the game being a 25FPS game on Spectrum, with two-pixel smooth scroll in both directions... this means I had to update the screen almost every interrupt (and, performance wise, this is a disaster!). At 7MHz, the Z80 code has almost no effect as bottleneck, but the game still needs frameskip (4 by 4 scroll) to keep pace with Spectrum speed; the game runs flawlessly without frameskip, but very slowly. And I could not just "forget about the framebuffer, plot directly on the screen", because the game simply uses the framebuffer to calculate the scroll. The game is so crazy that it even uses PUSH DE instructions to *plot the screen faster* on the VRAM. And every shape is shifted in real time to be placed on the screen, since the RAM space available was very tight. Probably these were the reasons why this game was never ported to MSX (despite the fact it is *old*). As far as I could research, almost all games that uses this kind of PUSH DE trick to plot screen were not ported (besides Astro Marine Corps). The difference here is the fact AMC was a 10~15FPS game, was not *fullscreen* and did not used framebuffer in the way GnG uses (well, AMC is, in my perspective, a supreme job of good conversion... I hope one day I will be able to do something like that!

pitpan: on 7MHz the game is "colorfull". Anyway, in Brazil 7MHz computers are far more common than any other MSX. I don't know how easy is the 7MHz update, but I really think it's very worth the effort. I try my best to make things work nice on 3.57MHz computers (I spent a lot of time adding things to speed up game in slower computers - namely MSX1, which forces me to add even more delay between VDP OUTs ), but I am not a magician nor will try to be. More profound changes in the original code would be as complex as rewriting the game from scratch. I will leave this job to those working on competitions like MSXDev or MRC Challenge.

ARTRAG: as Manuel said, I believe it's not a problem. Dvik's demo is very nice and it would be very cool to have a native GnG version for MSX. I love GnG series and I was missing it in my software collection. Since it was a Speccy 48 game - and a very hard to convert, since it was very videospeed-demanding, I decided it was a good place to start, to develop optimized base conversion functions (screen plot, speaker emulator, keyscan etc). But I really think a native GnG would be 1000% better than this port... at least it could be more colorful, faster and COMPLETE, with all levels.

I just like to say that it is very nice to receive comments after so much work, but I really like correcting/adapting games. So, my project is continue to adapt MSX cassete-only to disk (files) and convert some more Speccy games to MSX. I am sorry if some think this is a time waste, but this is what I like to do, and... since I do it in my free time, as a hobby, it is not a waste of time in any level. At least for myself.

Would be possible to prepare also ROM versions? It would be easy using the DSK2ROM tools, but maybe a straight conversion would be easier, smaller and more ellegant.

And of course, I didn't mean to be harsh or anything. I know how difficult it is, 'cause at the moment I'm also working on softsprites for MSX1 and I must say that it is both intensive in CPU and RAM usage, and the VRAM access bottleneck does not help at all.

So, keep the good work. But again, consider that perhaps an easier game (i.e. without scroll) would be easier and the resulting product could be easily run in a plain-vanilla MSX1 with 64 KB of RAM. For example, I was considering yesterday the possibility of an straight port of SIM CITY. I love the game and the ZX version is pretty impressive. But I let yo do it

Therefore, any ZX spectrum info will be welcome, of course.

Hi Fubeda, sorry if I gave the feeling I do not appreciate your work.
My comments suffered of my prevention against ZX ports, but
after having tried your game I have to admit that it is much
better than many other msx "native"games and by far better
than the average msx ports I have seen, (but this was easy )
Well done!

I think no one could say : 'Daniel is time wasted': i and other msx people greatly apreciate the effort. I think also that the only drawbacks are that whatever efforts could be, a msx1 3.5 mhz convertion is often undoable due to the differences between the machines, and due to the code that 'emulate' the speccy vram management. Different is the situation in 7mhz or more performant machines.....

However, Daniel keep up converting!, there is a lot greater probability to have a zx converted game that a msx1 game from scratch. Re-writing a game is extremely time consuming.

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Would be possible to prepare also ROM versions? It would be easy using the DSK2ROM tools, but maybe a straight conversion would be easier, smaller and more ellegant.

I don't know. :/
Zipped the game has 60KB, that means that the better compression we can get would require a 64KB ROM. Also, the game cannot run in ROM, since it has a lot of auto-modified code (both original and mine aditions). So, I believe it would only be a different way to package something without any real gain.

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And of course, I didn't mean to be harsh or anything. I know how difficult it is, 'cause at the moment I'm also working on softsprites for MSX1 and I must say that it is both intensive in CPU and RAM usage, and the VRAM access bottleneck does not help at all.

No problem, man. SLotman was pissed because it seems people wants to everybody to think the same. What is important to one is not always the same to another one. This is why SLotman and me stopped the "why don't you do this, why don't you do that" and started to do things the way we think fit. We all must learn to enjoy things as they are given to us... we must rejoice with nice additions like Space Manbow 2 (and not keep moaning about the fact "the background is static, they should have used screen 4".
We are in a very active community. At the same time there are people developing MSX1 games, MSX2 games, porting games, and so one. Some like better to develop MSX1 games, some like better develop MSX2 games and some ... porting games. I see no problem at all.

Yesterday I was reading about MSXDev discussion. I think it is nice the community discuss the limitations matter, but I believe the limitations change would only change "who" will develop. If it is decided it'll be a MSX2 game, then MSX2 game programmers will rejoice. If it is decided it'll be a MSX1 game with 8KB of RAM, minimalist MSX game developers will rejoice.
The important thing is: *more* programs and games available every year... and I believe we are the most active "old-computers" community in that matter.

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So, keep the good work. But again, consider that perhaps an easier game (i.e. without scroll) would be easier and the resulting product could be easily run in a plain-vanilla MSX1 with 64 KB of RAM. For example, I was considering yesterday the possibility of an straight port of SIM CITY. I love the game and the ZX version is pretty impressive. But I let yo do it

Humm... Well, let's say this game is very pretty in the top of my stack. Or has it already been poped? Who knows?
But keep in mind that with very optimized routines developed for GnG, porting a game simpler than it (b&w and/or with no scroll and/or with less scroll) can be a lot less difficult *and* with better results. This is why I choose a game that, from beginning, I knew it would only run nice on 7MHz (no matter how much effort I put on it).

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Therefore, any ZX spectrum info will be welcome, of course.

I will try to release something, but the docs are not fully complete. Much things are not correctly specified on the net and I am only able to correct/add data when developing (that is: reversal engineering). And since the docs will have the need to be translated (I need someone that understands português and english... and has at least a minimal knowledge of MSX and Spectrum hardware), I think its better to "mature" the docs first and then let them be translated. Translate a "work-in-progress" usually means a lot of lost work and also is the source for several errors on technical documents.

But I can say in advance that Spectrum is just a very nice hardware, even if it has its limitations (similar to MSX1, for instance). I am becoming more and more fond of the Speccy games and programmers while I am doing these ports. Very clever tricks, nice speed *and* space optimized routines... I am learning a lot about Z80!