Demo Vision

Discuss hardware-related topics, such as development cartridges, CopyNES, PowerPak, EPROMs, or whatever.

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Fiskbit
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Re: Demo Vision

Post by Fiskbit »

seijurou wrote: Tue May 24, 2022 3:45 am Hello all.

I have both systems, if any pic is needed please let me know.
Hi! Yes, that'd be very helpful! Could you take images of the top and bottom of the PCB in high enough quality that we can clearly see the traces and read the chip markings? That'd be a really great start. Images of both systems would be useful, too; based on the very low quality image we've seen of a Demo Boy, they might be the same, but we can't be sure yet. Any differences would likely be small, but still worth documenting.

Thanks so much for reaching out and offering help!
seijurou
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Re: Demo Vision

Post by seijurou »

Fiskbit wrote: Tue May 24, 2022 4:40 am
seijurou wrote: Tue May 24, 2022 3:45 am Hello all.

I have both systems, if any pic is needed please let me know.
Hi! Yes, that'd be very helpful! Could you take images of the top and bottom of the PCB in high enough quality that we can clearly see the traces and read the chip markings? That'd be a really great start. Images of both systems would be useful, too; based on the very low quality image we've seen of a Demo Boy, they might be the same, but we can't be sure yet. Any differences would likely be small, but still worth documenting.

Thanks so much for reaching out and offering help!
Perfect, I´ll send the pics later tonight or tomorrow.
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Ben Boldt
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Re: Demo Vision

Post by Ben Boldt »

OMG, please take hi-res photos of both sides of the board, where we can clearly see the traces. It would be greatly appreciated.

Edit:
Sorry I didn’t see page 2 with your reply Fiskbit.
seijurou
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Joined: Tue May 24, 2022 3:42 am

Re: Demo Vision

Post by seijurou »

Here is the pics, Hope it helps.

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Fiskbit
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Re: Demo Vision

Post by Fiskbit »

Thanks, that's some very interesting stuff! These boards are actually somewhat different, though it appears that the Demo Boy II is rev A while the Demo Vision is rev B, so it might still be that Demo Boy and Demo Vision systems of the same revision are the same.

The firmware dump that we have is from PRG rev B, so I'd be very interested in a dump of that Demo Boy II PRG rev A firmware. Would you be able to dump that? Given how little there is in the firmware, I'm not sure what could possibly have changed, so I'm excited to compare them. Also of interest for dumping is the U46 PAL on board boards, though I'm told that requires an adapter or specific programmer. I'm not sure yet what it controls, and I'm curious if it differs by board revision.

The Demo Boy top side image is unfortunately very difficult to make out, but it looks like that's a property of the board itself rather than an issue with the photo. Aside from that, I think these images are probably good enough, although if you can do higher resolution, it'd make things easier; the traces definitely blur together at times.

Looking over the Demo Vision board, which is much easier to read, it looks like the 8 KiB CPU RAM is hooked up to the CPU A11 and A12 lines, so I think this system actually does have a full 8 KiB from $0000-1FFF. All 6 DIP switches go to a hex inverter, and I suspect that inverter's output enable is controlled by joypad 1 /OE. The inverter outputs look like they're hooked up to CPU D0-D5, so reading $4016 should give all 6 switches. It's hard to tell exactly in the photo, but I think switches 1-6 connect to D0-D5, respectively. The firmware doesn't use D3-D5, so those switches should have no effect. I guess I'm not 100% sure how the switches read, but it looks like the hex inverter's inputs are pulled up by R6, so when the switches are open, they should read to the CPU as 0, and according to the datasheet, the switch in the up position is open. The image here, I think, shows switches 1 and 3 down, which would result in unlimited time, which makes sense. (Similarly, Chris Covell's had 1 and 2 down, which is an 8 minute timer, and he mentioned his system would 'randomly' reset.)

I'll continue looking over these to see what I can figure out, though I'm more of a software than hardware guy. If anyone more skilled than I can get insights into the unknowns I posted in the first post, please do let us know.


Edit: I've updated the Demo Vision page with these new findings.
seijurou
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Joined: Tue May 24, 2022 3:42 am

Re: Demo Vision

Post by seijurou »

Well I have no Knowledge about Dumping or anything I just was looking for game for my Famicombox collection and find this forum.

About the Demoboy 2 the pic of the traces of the chip, is almost imposible do a good picture becuse the lines are no so clear as the other one.

Actually i looking for trades for the demoboys for Famicombox games i miss, or maybe selling don´t know.

If any specific pic is needed i´ll be happy to help.

Here is some pics of my famicombox collection, sure you like it.

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Ben Boldt
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Re: Demo Vision

Post by Ben Boldt »

Nice Famicombox collection.

Thank you for the photos of your DemoVisions. Maybe we can get a better idea how this thing works now.
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Ben Boldt
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Re: Demo Vision

Post by Ben Boldt »

I am making progress using KrzysioPCB:
krzysiopcb_demovision.jpg
There are some areas where the traces are difficult to see and presently have me baffled. If I get enough of the visible stuff figured out, along with known pinouts, it should be possible to narrow down where the traces are going underneath the chips.
Fiskbit
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Re: Demo Vision

Post by Fiskbit »

Wow, Ben, this is incredible! Really excited to see how this progresses.
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Ben Boldt
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Re: Demo Vision

Post by Ben Boldt »

Thanks Fiskbit.
seijurou wrote: Wed May 25, 2022 3:01 pm About the Demoboy 2 the pic of the traces of the chip, is almost imposible do a good picture becuse the lines are no so clear as the other one.

If any specific pic is needed i´ll be happy to help.
Hi seijurou,

I am having some difficulty seeing some of the thin traces in crowded areas on the blue Demovision circuit board. However, when you zoomed in on the MMC5, the thin traces were extremely clear to see. I am wondering if you could take zoomed photos of each quarter of this board on each side, kind of like this:

Code: Select all

+---+---+
| 1 | 2 |
+---+---+
| 3 | 4 |
+---+---+
(A total of 8 photos.) I think it would be very helpful for some tough spots.


Edit:
One interesting note, I find that the CPU-RAM is a full 8 kilobytes in range $0000-1FFF. It is an 8k x8 LH5168 chip (U39) being mapped there by a 74HC139 Decoder (U29). Is this expected?

The decoder appears to be hooked up the exact same way as it is in the Famicom, producing /ROMSEL, CPU-RAM /CE, and PPU /CS (aka /DBE).
Fiskbit
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Re: Demo Vision

Post by Fiskbit »

I had the same conclusion about the CPU RAM, but don't know why they used 8 KiB here. The firmware doesn't require it.
seijurou
Posts: 9
Joined: Tue May 24, 2022 3:42 am

Re: Demo Vision

Post by seijurou »

Ben Boldt wrote: Mon May 30, 2022 7:46 am
Hi seijurou,

I am having some difficulty seeing some of the thin traces in crowded areas on the blue Demovision circuit board. However, when you zoomed in on the MMC5, the thin traces were extremely clear to see. I am wondering if you could take zoomed photos of each quarter of this board on each side, kind of like this:

Code: Select all

+---+---+
| 1 | 2 |
+---+---+
| 3 | 4 |
+---+---+
(A total of 8 photos.) I think it would be very helpful for some tough spots.
Image

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Image

Image

Image
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Ben Boldt
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Location: Minnesota, USA

Re: Demo Vision

Post by Ben Boldt »

That is extremely helpful, thank you!
seijurou
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Joined: Tue May 24, 2022 3:42 am

Re: Demo Vision

Post by seijurou »

thats great, i also like know more about the machines.
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Ben Boldt
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Re: Demo Vision

Post by Ben Boldt »

The new images definitely allowed me to find and fix a bunch of errors I made before. I don't have a great method yet to figure out traces beneath the chips. I think that figuring out which pins are inputs and outputs could help; I could rule out possibilities where there would be 2 outputs together.

I notice that CPU A15 appears to go out to the Gameboy on the P2 connector. Why on earth would it do that? I think I must have made a mistake because I can't imagine any possible way that would be useful. That signal is going to be constantly toggling when executing from ROM and using RAM.

U13 and U25 must be the RAMs that store the Gameboy video image. U38 is CIRAM. U45 is the normal Famicom latch that turns PPU AD0..7 into PPU A0..7. It is pinned out the same way as in the Famicom.

Are you interested to see it; would you like me to find a free file upload website? It zips to 8 MB which is too large to upload directly here.
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