A couple things so far about the Gemei MAME4ALL port:
1). Sound is laggy. This issue has been touched on before. At lower sound sample rates, the sound seems to lag - badly. This seems to decrease at higher rates. I'm going to go with the following approach:
There are two sample rates to consider: The emulated rate and the Gemei's playing rate. For most emulators and systems, these are the same. ie. For my versions of MAME4ALL this is always the case.
To help solve the laggy issue, my workaround will be to set the Gemei's sample rate to the maximum 48Khz stereo but still allow MAME4ALL to emulate at lower sample rates (for speed reasons). The emulated sound generated by MAME4ALL will then be resized to fit the number of samples the Gemei is expecting to play (which is a pretty quick step). Obviously if MAME4ALL is set to 48Khz stereo then there won't be any need for "resizing". Complex sound chips like the ym2151, would take a lot of processing at this maximum rate which is why I prefer to emulate it at a lower rate and then re-sample it at the last output step to the Gemei.
2). The Gemei is making use of Cyclone and DrZ80 CPU cores. Great! I've tried some games that really torture MAME4ALL, Outrun is a good candidate having 2x M68000s and 1xZ80. It runs pretty well - though not stellar. I guess the issue is that the Gemei's CPU is an ARM-926 - same as the GP2X Wiz. Whilst on paper the specs seems to indicate it should be super fast, I've found it isn't. And this seems to hold true with the Gemei A330 too.
3). Extra RAM. This is probably the best advantage of the Gemei A330. Glorious extra RAM! We have much more user RAM to play with - 30MB of Heap and 8MB of program space. This was a main issue with the Dingoo A320. Lack of RAM - it only has 16MB Heap and 6MB program.
The extra RAM is good but unfortunately will still mean the Gemei version will need a number of executables to cover all the games - I'm thinking 4 or so module. The Dingoo A320 has 8 modules.
4). Hardware screen scaling! I love hardware screen scaling! In the process of getting this working. Using Rampage as the test subject as it's game resolution is 512x480. And I also like Rampage ;-)