Hello my fellow Freaks!
There's some final design work yet that needs to be done before I send the boards off for production but I wanted to show a first look at what the boards for my video game arcade system will look like!
I used the EagleCAD files and created some basic 3D designs to see how things would look. This image does not include the game controller.
You can see I've labeled each of the major ICs. What do you guys think?
Why so many chips?
Why so many chips?
All of the unlabeled SOP chips on the larger board are logic transceivers for the VRAM addressing and video output. The one that's unlabeled on the cartridge board is just a level shifter for the Flash memory.
Naa.. Do it Atomic Zombie style with a Tiny45, 2 resistors and a safety pin
If you don't know my whole story, keep your mouth shut.
If you know my whole story, you're an accomplice. Keep your mouth shut. 
Is the CPU on the game card?
That looks a lot like this one!
Is the CPU on the game card?
When we designed/sold a games console (GX4000 - anyone remember?) the "cartridges" were nothing more than an EEPROM (later masked ROMs) and an "unlock" chip to do with protection that meant others could not easily duplicate our cartridges. Everything else lived in the console itself (basically a CPC464+ in a small box).
EDIT: Hey I just read the Wikipedia page I linked to. I am officially famous!!
(I wasn't the designer though - wonder who made that mistake?)
EDIT2: OK so this is a fun new game. Search for references to your own name on Wikipedia. Sadly of the 9 pages that mention "Cliff Lawson" only 3 are really me.
Yes, I would expect game cartridge to be quite simple, unless the idea so to have an upgradeable "CPU card". It's a bit hard to tell just from the picture.
Isn't it the chip marked "System" above then? (though it's true that "Game" having more pins than "System" seems curious).
Judging by the package and placement of crystals, there appear to be 4 CPUs - Game, System, Audio, Video, although some could be FPGA I suppose.
Is the CPU on the game card?
Yes, the game cartridge has it's own dedicated CPU.
When we designed/sold a games console (GX4000 - anyone remember?) the "cartridges" were nothing more than an EEPROM (later masked ROMs) and an "unlock" chip to do with protection that meant others could not easily duplicate our cartridges. Everything else lived in the console itself (basically a CPC464+ in a small box).
As you guys know since the ATmega chips do not execute code from ROMs, this was the reason I decided to put a CPU chip on the cartridge. It also has it's own dedicated external RAM (1 MB) and Flash memory (8 MB) for audio, graphics, levels, etc. The dedicated video chip on the system board handles the VGA video generation and renders the front buffer from one VRAM buffer while the game cartridge pumps sprites to the second VRAM buffer and signals the video system to flip the buffers (only a single clock cycle bit flip).
The system chip right now actually does not handle very much. The name is actually very inaccurate because I haven't really figured out what to call it. It handles system boot up (showing the custom launch screen, ala "S-E-G-A!" on the Genesis) and then passes control to the game cartridge CPU.
EDIT: Hey I just read the Wikipedia page I linked to. I am officially famous!! (I wasn't the designer though - wonder who made that mistake?)
That is so cool that you worked on that! Can you talk about what all you were involved with on the project?
Yes, I would expect game cartridge to be quite simple, unless the idea so to have an upgradeable "CPU card". It's a bit hard to tell just from the picture.
The intent was originally to be able to have a beefier processor such as an ARM processor but that requires some extra care due to the lower voltage than the rest of the system. It can still happen but has not been a large focus as of late because I want to get things in production. I've spent a lot of time designing and prototyping all of the major pieces and it's time to put the pen down and finalize things.
Judging by the package and placement of crystals, there appear to be 4 CPUs - Game, System, Audio, Video, although some could be FPGA I suppose.
That is correct. No FPGAs on the board. The 3 main CPUs on the driver board are all ATmega644 and the larger CPU on the game cartridge is an ATmega6450.
EDIT2: OK so this is a fun new game. Search for references to your own name on Wikipedia.
OK - I'll start: https://www.avrfreaks.net/forum/f...
As you guys know since the ATmega chips do not execute code from ROMs
Well you see, you may know it is ATMega, but since you didn't say, how could we have known? :)
I suppose ATMega is cheap enough to use as a Flash memory, but I guess most designers would put CPU on baseboard (one that supports external bus), so I would say the design choice is "unusual".
That is so cool that you worked on that! Can you talk about what all you were involved with on the project?
While I had a hand in a lot of the software and wrote a lot of the acceptance and factory tests for all the new features it would not be true to say that I was the designer as that Wikipedia page suggests. I was just one of a team. The majority of the "clever stuff" was done by Steve Gane in hardware in fact - he designed the ASIC.
Cliff, thanks for the wonderful explanation! That's very cool! :)
Jamison wrote:As you guys know since the ATmega chips do not execute code from ROMs
Well you see, you may know it is ATMega, but since you didn't say, how could we have known? :)
I suppose ATMega is cheap enough to use as a Flash memory, but I guess most designers would put CPU on baseboard (one that supports external bus), so I would say the design choice is "unusual".
Well, that's definitely a point! Haha
As for the Flash memory, the CPU is not acting as the Flash memory. It's got an external Serial 8 MB Flash memory chip. The Game CPU will load graphics or audio from the SPI and dump them into the RAM chip on the game cart which also has a direct data bus to the back buffer VRAM, making sprite/pixel plotting fairly fast.
Can this be better designed to simplify the game cartridge and move the CPU and RAM to the driver board? Absolutely. There's a couple reasons why I made the design decision to do it the way I am: It allows the games to be "upgradeable" in a way by allowing faster CPUs or more RAM or Flash memory, and the second is I am physically limited to 160mm by 100mm in the board size because I only own the personal edition of EagleCAD. Routing the main system board was already fairly tough in some areas even at that size. The professional edition being almost $800, I'm not at that point yet.
I am physically limited to 160mm by 100mm in the board size because I only own the personal edition of EagleCAD. Routing the main system board was already fairly tough in some areas even at that size. The professional edition being almost $800
You wouldn't have that problem if you used KiCad, I would really recommend giving it a go on the next board you design. Sure, there is a bit of learning curve, but there are no limits.
You wouldn't have that problem if you used KiCad, I would really recommend giving it a go on the next board you design. Sure, there is a bit of learning curve, but there are no limits.
Thanks for the recommendation. I will definitely give KiCad a shot on a new board design and see how I fair with it.
You need to put some of these babies on that thing:
You need to put some of these babies on that thing:
