Hi. I have this weird adaptor for the Megadrive / Genesis. What I think it does, is add 'extra power' or additional buffer RAM or something like that. I know this, because when I play something such as Sonic 2 without it, and drop 100 rings, the Megadrive lags out and the FPS drop. With it, this does not happen. I do not play with it, because if I bump it the game will freeze and it is not reliable as it is like a tower... Here are some images of it. It would be better, to just solder inside the Megadrive to the correct pins the chip for optimal performance and no more FPS drops... http://www.box.net/shared/fchal5hijdxjnhm64sgh http://www.box.net/shared/hcoc18crsjvzulsqz25a http://www.box.net/shared/nijy922cvdevvqohz6gs
The chip is a Programmable Array Logic chip so it's not high speed ram or anything like that. All the chip does is to override the jumper switches in the Megadrive, this one will allow you to play american games on a PAL system.
Oh. Well, I was WAYYYYYYYY off then - haha. But then why does the lag stop when I use it wit Sonic 2 (PAL)? *EDIT* IC is CPL20L8-25NC
The lag stops as the game is running at 60Hz as apposed to 50Hz. The chip is not a COP8 microcontroller, the datasheet for the chip is this one... http://www.ic-on-line.cn/download.p...89A2254E770&file=0272\cpl20l8-25nc_429722.pdf
Thank you very much. I suck when it comes to finding the right datasheet... Making it run at 60 hertz, produces more heat from the CPU though correct?
Don't worry about it making more heat. I've run pal megadrive's in 60Hz for years and never had a problem
Haha, I know the heat will be minimal, but I just wanted to know if it would increase the heat output. And it does. Thanks! I will solder this microcontroller inside my modded SEGA Megadrive II with a switch on ground.
Er, if you are going to do that then you might as well fit a switchless mod or even just two switches, as all this chip does is force the machine to a 60Hz state and if you are going into the machine then you might as well mod it yourself.
Well I already did the S-Video mod and made the LED green. I want to make it so the LED goes yellow (get one of those voltage sensitive colour LED's) when the console is off and green when power is active... So it is a standby light... Would also like to do this with my PS1...
Switching between NTSC and PAL doesn't affect the CPU speed at all, the MD always divides the master oscillator by 7. Also this thing doesn't even change the VDP frequency, it simply overrides the status register to trick software into running.
Maybe this prevents slowdown by making the software 'think' its running in NTSC mode (lower vertical resolution) but actually providing more raster time because it is running in PAL. When that is the case, you should notice extra borders on the screen?
I dont know if there are extra borders. The thing does not work. I tried for an hour, cleaning all the terminals and still nothing. I did the region mod instead, and I am going to put a oscillator to make the 60 hertz (when active) run at a certain frequency. This will give me colour.
This thing only changes the region when the game tries to detect it from reading a specific I/O register. It's used to bypass region lock for protected games but it actually does not change the VDP refresh rate so most game will still be running at 50fps. That's said, a few games (Sonic 2 is one of them I think) will not use the VDP refresh rate for main synchronization (VSYNC) but rather use CPU cycle counts. Those games are generally designed to run on both PAL & NTSC hardware without speed differences (similarly as PAL-optimized games) and use the detected region to adjust their speed on startup. These games can therefore run faster if the region is set to NTSC but the fact the VDP is still running in PAL mode can cause glitches later in the game because of timings incompatibility (indeed, PAL has more lines per frame and so can return different and unexpected values when the VDP status or HV counters are read).
