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Cartridge Emulator
lazereyes - Jun 27, 2005

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  lazereyes Jun 27, 2005
I've had the idea for years but never bothered as my electronics is limited but with modern USB and parallel connections would it be possible to emulate a cartridge which plugs in to a real Megadrive? Then the PC could act as a massive multi-cart....

What you think? :huh

LE

 fonzievoltonov Jun 27, 2005
Assuming the time of a "Parallel > USB > COMPUTER > SOFTWARE > COMPUTER > USB > Parallel" communication which is certainely over 10ms, the genesis could crash (it needs 150-200ns responce time).

I think it is impossible.

 it290 Jun 28, 2005
It could be done if the unit had a bit of flash memory (or even just plain ol' ram), with boot code in ROM. Basically, the same concept as the Sega Channel unit. But as far as just sending info directly to the Genesis with no buffer, nah, I'm in agreement with fonzie.

 Mask of Destiny Jun 28, 2005
I thought about trying to do this with a custom ISA card, but it just wasn't fast enough. Parallel and USB 1.1 would definately be too slow. USB 2.0 would probably be fast enough, but the latency probably would still be too high.

You could do it as a PCI card, but it would be easier (and probably more cost effective) just to make a RAM cart that could be quickly refilled by the computer.

 fonzievoltonov Jun 29, 2005
Sram is damnly expensive...

Some times ago, i searched for some parts (to make a 4MB ram, then flash cartridge) it was approx 300USD for a 4MB/16bit SRAM ...

 Mask of Destiny Jun 29, 2005
DRAM controllers aren't that complicated. Probably less complicated than writing your own PCI bus logic.

I did find someone on e-bay that was selling NVSRAM for what came out to be ~$30 US for 4MB. Pretty sure it was new and they were nice easy to use DIP packages as well.

 lazereyes Jul 3, 2005
Ok -

How about this - a cart made up of Standard simms - with some kind of boot loader , this is connected via usb to PC - cart communicates with software running on PC to get a directory listing - software on the cart boots up on Megadrive and gives you the listing to choose ROM from , the rom you choose is sent via USB to the simm cart and then boots up as normal. The idea being to use the PC as a hard drive/cdrom rather than trying to make a flash cart (which I've seen somewhere for only 40-50 UK pounds)

LE

 ExCyber Jul 6, 2005
What you're describing is basically similar to the Doctor V64 Jr., except that's for N64 and has a parallel interface instead of USB. I think it would end up being better to stick a CompactFlash or MMC slot on there instead of a USB interface, though, because that way you wouldn't need a PC for the cart to be useful.

 it290 Jul 6, 2005
CompactFlash would be good; that way you could interface with it using normal IDE device commands.

 maiki Jul 26, 2005
There is actually a very interesting project on allmighty Commodore-64 called IDE 64.

http://www.volny.cz/dundera/...

I think this is the right way - Mega Drive has always been a very portable arcade gaming system and we should not mix it with bumpy PCs. INstead I woould provide it with a massive media card and here we go!

 ExCyber Jul 27, 2005

  
	
	

		
		

			CompactFlash would be good; that way you could interface with it using normal IDE device commands.


I'm not sure how much hardware a really basic ATA <-> 68000 interface would need, but on the SD/MMC side there is the SPI Flash standard that should be able to be bitbanged with minimal hardware using some interesting combination of the cart control signals; the CPU/system bus utilization would be absolutely atrocious, but it wouldn't matter since it wouldn't have much else to do. Interfacing the DRAM would really be the more challenging side of it.

 Mask of Destiny Jul 27, 2005
ATA is dirt simple. Really all you need is some simple logic to manipulate the ATA address lines so that the bus goes into a Hi-Z state. Everything else can connect pretty much 1 to 1.

 lordofduct Jul 27, 2005
If your gonna go through all this trouble, time, money and everything... why wouldn't you just make an IDE interface like that one guy and hook a dedicated HDD up to the thing? What was that guys name...? He made the MegaDrive PC.

I think he is a member here but never posts. I know some of the major users here know who I am talking about, Cybie, Mask, it290 you know who I'm talkin' about?

 fonzievoltonov Jul 27, 2005
Yeah, Devster

 Mask of Destiny Jul 28, 2005

  
	
	

		
		

			Originally posted by lordofduct@Thu, 2005-07-28 @ 06:23 AM



If your gonna go through all this trouble, time, money and everything... why wouldn't you just make an IDE interface like that one guy and hook a dedicated HDD up to the thing?


The HDD/Flash drive interface isn't the hard part, it's the RAM needed to support the drive. A processor can't run code directly from a hard drive, it must be first loaded into RAM and so in order for this to work you need to add RAM where the cartridge would be. Large quantities of SRAM tend to be expensive and DRAM requires relatively complicated logic (compared to an ATA/IDE interface anyway).

 maiki Jul 30, 2005
anyway, one can always go for software emulation (advance mess...)

 lazereyes Aug 14, 2005
you could, but emulation is never ever the same as the real hardware.

 maiki Aug 19, 2005

  
	
	

		
		

			Originally posted by lazereyes@Mon, 2005-08-15 @ 07:37 AM



you could, but emulation is never ever the same as the real hardware.




[post=138315]Quoted post[/post]


You are absolutely right. Emulation is MUCH BETTER than the real hardware.

What is actually "the real hardware"? I have got a Mega Drive II but when you open it, there is not any Z80 or MC68000. You can just find some weird custom (emulation) chip labelled SEGA. So is this the real hardware you mean???

The reality is as strict as follows:

an emulator delivers much better performance on both video and audio engineering of Genesis / Mega Drive games

on the emulator one can easily get 44 kHz stereo (!!!) audio output, this never ever can be compared to that awfull noise produced by "real" hardware

the VDP emulation on all the emulators I have tried is designed to overcome that stupid buggy sprite displaying limitation... much much better than "real" hardware

The concnlusion is as simple as that. Emulation is the only future for not only Mega Drive but all the others.

see ya :cheers

 Mask of Destiny Aug 19, 2005

  
	
	

		
		

			Originally posted by maiki+Sat, 2005-08-20 @ 01:01 PM-->
QUOTE(maiki @ Sat, 2005-08-20 @ 01:01 PM)
What is actually "the real hardware"? I have got a Mega Drive II but when you open it, there is not any Z80 or MC68000. You can just find some weird custom (emulation) chip labelled SEGA. So is this the real hardware you mean???[/b]



Just because the 68K and Z80 have been integrated into a custom chip doesn't mean they aren't there.


  
	
	

		
		

			Originally posted by maiki+-->
QUOTE(maiki)
on the emulator one can easily get 44 kHz stereo (!!!) audio output, this never ever can be compared to that awfull noise produced by "real" hardware[/b]



All the PCM samples are still as low bitrate as they were on the real thing. The only thing that has changed is the number of samples produced for the FM synthesis, but audible difference is relatively small. Though I have heard at least some Megadrive 2's have weak power supplies which cause distortion on the audio output. Perhaps this is why you feel the emulator is far superior in the sound arena.