Tom: Unless I got confused along the way shubibiman and I were discussing a card that one could use on a Duo that would add SGX capability. Since a flash card from Tototek is $50 by itself and isn't even in the same universe capability-wise as these cards we are discussing (which are in may ways more complex that the PCE itself) I can't imagine the cost being anywhere near as low.
Ohh... Well, the setup I was talking about wouldn't be that expensive as long you don't mind it looking like this:
Which I don't. Anything more fancy like a real looking hucard is going to be more expensive.
I agree that the audience is small, but viability is a balancing act. There are homebrew hardware addons for the DS (such as the motion sensing card) that don't have any use with legit software. Obviously the DS market is at least 1000 times the size of the PCE market, but PCE people are crazier so maybe they can make up for their lack of numbers by individually putting more $$$ into the scene. (Think Neo Geo here).
Yeah. It is a small target audience. But wouldn't it be a treat for owners of such SGX CD combinations get a cool homebrew soft? I personally think so. And, it's not like the SGX is some convoluted beast and hard to code for. It's just as straight forward as the PCE's video hardware, but really lets loose some of the original limits of the PCE. Imagine games running completely in 512x232 res. SGX has the realistic vram amount for it. SGX has the realistic sprite bandwidth for it. And a second BG layers makes things less complicated for scrolls effects. Not that I don't like a challenge and pushing hardware limits, but sometimes it's nice just to have the hardware directly for you.
Adding SGX compatibility via the HuCard slot: Is this possible? Seriously possible? And if it is possible, would be in any way reliable?
I've looked at this situation a while ago and what's doable. IIRC: From what I've looked at, it appears not 100% doable because of some mirroring issues of the original PCE. That's not to say that they couldn't have just made the SGX as an upgrade to the PCE originally. Given all the pins on the back, they very well could have. So, I *think* the problem might be mirror issues (otherwise if it was open bus, it wouldn't be a problem). If I remember (a few games access this mirrored area, thus the switch they put on the SGX to make it more compatible). This would cause bus conflicts. You can definitely at a version of SGX on a card. But the memory mapped I/O would be in different locations. Any new soft would detect which "SGX" setup, and use the correct address I/O's. You'll also need to have another VCE and redirect all writes to the original (so more hardware). And the biggest problem; you'd have to do analog mixing. Normally, the SGX handles all mixing digitally because the VDP(s) output it's data in digital pixel form. But since you don't have access to this on the cart port, you need to manually mix the two VDP signals. That means a composite scanline sampler (a quite easier it required it to only RGB input though).
If this were an addon via the backplane of a non duo unit, you don't need the analog mixing part. But the backplane isn't going to solve the mirroring(bus conflict) issues. You'd have to open up the system itself and make some modifications to remove the mirroring.
So, you could make an SGX card per se, just not one that is backwards compatible via ports. Though software can be easily mapped to use an alternate mapped ports - but is only for future SGX softs and not backwards compatible existing SGX hucards. Did I mention this would be
expensive and will most likely require a separate power supply to this card?
Well, it's not entirely true that you can't do an SGX as a card addon. You could do both VDC's on the cart, and redirect original VDC read/writes to one of the primary VDC on the cart, and VCE/VPC/VDC#2 address writes to those on the card too. No need for analog mixing as you have all the digital pixel data you need right there. And the original VDC, since it has the same settings as the duplicate, still generates the interrupts you need and on the right vector (no SGX soft that I know of uses interrupts from the second VDC. There's no need to). So that means you need to have a VCE, 2xVDC, VPC on the cart. And, you need to find some way of syncing *ALL* of these chips with the VCE and VDC of the original console (because you need scanline interrupts to match up). That means running the composite output to the cart for the initial sync and any resync'ing. Oh and the last condition is: you can't read vram from the second/SGX VDC. As long as no game does this, then it'll be fine (I don't see why they *would* read vram back into main ram, but you never know with devs. The cool thing is, is that you only have like 5 games to test to see if this is the case). Reading from vram of the primary VDC is not a problem, because you're reading the duplicated data inside the original VDC. This card would probably still require an external PS. And yes, that would be expensive still. And 2 or 3 fast fpga's. The VPC and VCE can easily be combined into a single chip since they don't do very much. Probably condense the 2 VDCs into a single chip as well.
Remember a while back we were talking about how for some reason some games no longer worked with certain hardware combinations after grounding pin#29 on the Hu6280? I think it was the SuperCDROM2 when combined with a SGX that didn't work with some random games. Does anyone have the slightest idea WTF that happens?
It's not the SGX. It's the Super CDROM^2 unit itself (though the SGX *does* have this yellow wire modification inside the console, going to the back plane to the cart port. Might be this pin specific pin? Maybe not all SGX's got this mod from the factory?). I have a PCE and tested it on the unit. Came up with the same problems. Bubble Gum Crash had problems detecting BRAM (didn't see it, IIRC). The tototek card totally fails though with the SUPER CDROM^2 unit. It'll corrupt BRAM if a flashed hucard tries to access it. Lost all my save files because of this
But the ACD Pro, the Super CD 3.0 card, Tonoke back up card, all have no problems accessing BRAM on that unit regardless of what main system is attached. Definitely weird.
The Tototek card: This thing is not famous for its reliability and ease of use, even though its made by rather experienced guys. I'd gladly buy a System Card 4.0 for any reasonable price (say, less than $200) but is has to actually work...more or less perfectly. No proprietary software that doesn't run half the time, thank you, and I don't even own a machine on it with a parallel port so f*ck that shit.
It's been very reliable for me. And very easy to use the programming software (just a gui where you pick roms, add cheats, enabled bit swapping, etc). It's finding a system and setting up the parallel port that's always been a bitch. It took a bit of messing with bios to get it to work on this motherboard. I could not get it to work on another tower I had, regardless of the settings. USB interface would be sooo much better though.
