Thursday, March 23, 2006


Sega Master System emulation improving

I've rewritten parts of the video emulation to render per scanline instead rendering once per frame.
This has improved compatibility and accuracy for quite a bit, because effects done by changing video registers in line interrupt handlers are now emulated correctly.

Also, performance has been improved dramatically. I can now easily run 4 or 5 SMS emulators at once at full speed on my not-so-new Athlon 1800XP machine, which I think is not bad for a java based emulator.
There's even room for more optimizations (caching of decoded video tiles might help for example), but I think I'm satisfied.
Performance problems are always temporary problems so I'm not too obsessed with it (who wants to run multiple SMS emulators at once anyway?), but it's still a nice side effect of the recent changes.

Last but not least, I've made some utilities which makes it very easy for me to add support for online high scores in more games. It now takes just a few minutes per game, tops.
The parameters of the online high scores per game are also not hardcoded in the source code anymore, but are now loaded from config files.

Friday, March 17, 2006


JEmu2 does Sega Master System!

JEmu2 now supports a classic console: The Sega Master System.
It currently fully supports sound, and even has support for saving your scores on the internet (currently implemented in 7 games, for example Sonic The Hedgehog).

There is still some room for improvement though. For example the renderer is a frame based renderer, which means that video emulation is only done once per frame.
In some games though, this isn't enough because they use some tricks which requires the screen to be updated more often.

For example, the palette may be changed a few times during video updating so that there can be more colours displayed at once than the official hardware specifications allow for.
Thus, such games are not emulated perfectly yet.

The same goes for sound updating, which is also only done once per frame, so digital sound effects do not work yet.

I did however keep track of the horizontal scroll register each line, so for example the road in racing games are still displayed properly.

The Sega Master System is a fun system to emulate: It's not too difficult compared to get some games to work, but it's still a good challenge to make it accurate and compatible.

Check it out at the official JEmu2 homepage!

Friday, March 03, 2006


MSX2 emulation improving.

Working on improving the V9938 instruction set emulation is starting to show results. Next release, JEmu2 will be running a game which is often touted as the best MSX2 game ever: Metal Gear 2: Solid Snake. And it now finally works perfectly!

People who know this game often regard the game Metal Gear Solid, which first appeared on the PlayStation, as a 3D remake in terms of story, events and gameplay.
Metal Gear 2: Solid Snake game is quite unique in the sense that it is the only 'real' successor of the first Metal Gear game, and the MSX2 was the only platform it has been released on (the first Metal Gear game has been developed and released first on MSX2 as well).
There has been been a Metal Gear 2 released for the NES, but the original game designers were not involved in that and the game turned out as a real disappointment, sharing none of the qualities of the successful first Metal Gear. Even the story has no connection with the Metal Gear saga whatsoever.

Fortunately, an official Metal Gear 2 was made by the original designers from the first Metal Gear, the still very successful Hideo Kojima being the most important, and this version was not only a worthy successor but a fantastic game in its own right as well.
The only downside of the official Metal Gear 2: Solid Snake was that it exclusively appeared on the MSX2 (a system which was only successful in a few countries), and it was also only released in Japan, so difficult to understand by people who don't understand japanese, if they could even get a hold of this game in the first place.
Fortunately, Metal Gear 2: Solid Snake has later been translated to English by fans (so it's not an official translation), and this is the version which will appear on Now finally everyone can see what a wonderful game Konami has kept from non-japanese and non-MSX2 users.

There will be a few more games in the next release of JEmu2, such as Arkanoid 2: Revenge of Doh and Contra (a.k.a. Gryzor).

Thursday, March 02, 2006


JEmu2's Development blog

V9938 emulation progress
I finally got the V9938 instruction 0x0F working (high speed put bytes CPU->VRAM) and the instruction 0x0E (high speed Copy Vertically), which made Gryzor/Contra playable, fixed some missing graphics in Vampire Killer (most notably the doors at the end of the levels) and made various other games work somewhat better.

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