Hi guys, I suspect a handful of you may recognise my username from other forums. Not quite sure why I've never registered here before, as I've been directed to some pretty technical and helpful posts in the forums here over the years. I'm pretty impressed with the collective knowledge that is imparted in these forums to be honest. I've been interested in emulation of classic gaming hardware for well over a decade now. Initially software only, but in recent years it is primarily FPGA emulation of gaming hardware. Professionally, I'm an electronics design and software engineer, which has included a decent amount of FPGA work over the last several years. Most of my own efforts in the emulation area have admittedly been 90% complete 'proof-of-concept' efforts as part of a larger, more ambitious project. But my interests cover most of the mainstream retro console, micro-computer and (perhaps most significantly) arcade hardware. Jack of all trades, master of none I suppose. My most recent project is to produce an emulation of the Neo Geo MVS & AES systems on custom-designed prototype hardware. It's an ambitious (and costly) project that is going to take many months to complete, but I'm intending on taking a decent stab at it as it's probably the 1st project I've undertaken that has a viable market for a finished product. But that's even further away again. Along the way I'll obviously be immersing myself in the technical details of the Neo Geo primarily, but my technical interest in the other hardware won't be diminished. EDIT: I should also add that I have a passing interest in development for these platforms as well. I've done a few ports of titles from one platform to another, and always interested in collecting programming information as well as hardware documentation.
Sounds like a fun project- but I can see that sprite engine in the NeoGeo taking up quite a lot of LEs / Logic cells and RAM resources based on the quick look I had at it once. I guess the other bottleneck is going to be emulating all the memory spaces that exist on a NeoGeo cart - I don't think you could multiplex a single memory system (especially something high latency like SDRAM) across all those buses and still hit the latency requirements for. I guess you could design it with a socket for real carts, but where's the fun in that
You're spot on there of course. I've been emulating various platforms for quite a few years now, and took a look at the Neo Geo some time back on hardware that wasn't up to the task of a full system emulation. However, I did manage to get the MVS BIOS booting and JoyJoyKid running with the fix layer only. You could actually coin up and "play" a game... Since then I've acquired access to more powerful platforms, but still nothing suited to Neo Geo. The sticking point as you rightly mention is the 5 buses on the cartridge connector... So I finally bit the bullet and decided to make a real go of it, and design a purpose-built platform for Neo Geo emulation. It will double as my 'generic development platform' for all my other projects for quite a while, so it's ridiculously over-spec'd even for the Neo Geo. Aside from a massive FPGA, flash for all the on-board ROMs (hey, it's dirt cheap), some SRAM and SDRAM (probably unused) it also has both MVS and AES cart connectors and SD card. The purpose of the hardware is to make the job as easy as possible, as a first-pass. Once I have what is essentially a (very, very expensive) replacement motherboard, I can look at not only de-scaling the design but also alternatives for the cartridge storage etc.
Ah, OK - I guess I was thinking of a rather less targeted platform than the one you have in mind. I guess the obvious next question is if you intend to connect the flashes directly to the cart buses (presumably with the high order address lines broken out for custom chip magic) or just make the flash arrays completely generic and route them inside the chip. I you go for the latter, I guess you will need an FPGA that not only has a lot of logic, but a lot of IO too. Is there a freely available cycle accurate (and otherwise accurate :smile-new 68k core? I can't remember seeing one, but I have to admit I haven't looked - although I guess if you have enough IO you could just hook a real CPU up to the FPGA and know that the behavior is 100% correct. That would also mean that if you ever decided to implement a soft core 68k you would have a ready source of verification data.
Even with the largest FPGA, I was limited by the I/O. So by necessity any flash device that is on a cartridge bus is routed externally to the connector as well as the FPGA. All extra flash I/O goes to the FPGA, so each device is fully usable (and independent) for other designs. The only doubling up I had to do was the BIOS flash and the SRAM. There is a freely available 68000/020 core (used in Minimig, Atari ST, Sega Megadrive) but I don't believe it is cycle accurate (yet). That aside, you read my mind; there's a "CPU Socket" which actually takes a small daughterboard and is (just) adequate for a 68K. I will also be using it for verification of my own cores (eventually). I've got a 6309 in the works... More info here.
...Certainly better than a master of one! Welcome aboard, good to see another Sydney-ite join the ranks! :smile-new: I was a bit worried there for a while that I was only going to have Victorians and Queenslanders flanking my sides! Regarding your custom-made hardware, you'll be documenting the whole thing I take it? No doubt one day, someone would be able to use that sort of knowledge. I for one, wouldn't have the slightest on how to do that without extensive research and learning... But a guide sure would make things easier! :congratulatory: Enjoy your stay!
Argghh - can't think of anything worse. Well you're not alone any more! The hardware design is straightforward, nothing interesting. The VHDL on the other hand... it'll remain proprietary for the time being, but I guess eventually I'll release it into the public domain so it's not lost forever should I get hit by a bus... There's another response from me in this thread awaiting moderation atm which has a link to the project blog... BTW had a look at your site - very, very interesting indeed! Your Sophia looks awesome! I'd like to know the story of how you came to possess it!?! Do you also have the development software that runs on it? Are you planning on doing any evelopment on it, or is it simply for your collection? Since you're in Sydney maybe one day I can convince you to let me touch it if I give you a live demo of my Neo Geo running!
And that's why I use Google for images, they aren't going anywhere for a long while yet by the looks! :encouragement: Not even a bus can stop Google! That's a negative on development (I'm not as crazy as some of the others on here!) since there are much better tools available these days. I suppose I am more a hardware collector than anything. The games are there, but it is the hardware that does it for me! Haha, maybe one day! I'll need to get into Neo Geos first... I've still got a long way to go! I think a party would be the best way to celebrate! Edit: Forgot the Sophia story! Purchased as completely broken from eBay in Japan, it was originally to be used as a conversation piece. It became much more than that when a member on these boards was kind enough to donate some SH-2 CPUs to give it life again! Oh and all that jazz about capacitor replacement, etc! :loyal: I should really fix up my website... so much to correct... I really should have some dedicated pages to the more unique hardware. But how to arrange it? :grief:
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