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PostPosted: Thu Jun 26, 2014 1:37 pm 
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Have you got the pinout differences?


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PostPosted: Thu Jun 26, 2014 1:48 pm 
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Pinouts for 2 different MMC3 clones are at Romlab http://nintendoallstars.w.interia.pl/romlab/pmmc3.htm

Mislabeling is possible I suppose, if they were mixed together somehow. The working ones definitely seemed to work, tests I did were with SMB3 and Double Dragon 3.


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PostPosted: Thu Jun 26, 2014 2:11 pm 
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Yeah the ones that worked for me worked great as well. Tested with Batman, Megaman 3 and 5, Little Nemo. But these other ones baffle me...I don't think it could be a mislabel on some of these, as the game appears to work somewhat, albeit very glitched out. The other chips pinout is way too different for the game to even get that far.


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PostPosted: Thu Jun 26, 2014 9:08 pm 
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How many of them are defected?
Are they defected in the same way?
For example 6 or more of them have the same behavior and output


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PostPosted: Thu Jun 26, 2014 9:22 pm 
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Of the 10 I tested, only 2 worked right. It was several years ago, but I remember the defective ones mostly glitched in different ways. I'm pretty sure at least one of them got really hot too, like getafixx reported.


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PostPosted: Thu Jun 26, 2014 9:34 pm 
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Memblers wrote:
I don't know if we could ever know for sure, but my theory is that all the good chips were built into carts years ago, these were from a known bad batch that was set aside and never used, or were thrown out and someone pulled them from the trash. I have a hard time believing that that many defects could be normal, but I suppose that's possible too.


I think that has a substantial chance of something along those lines being the case. When I first heard about this being a common issue with these chips I had a hard time coming up with a rational explanation for the high rate of defect. At that time part of me wondered if it was just bad testing practices by whoever was making those reports years ago. But here you are years later with a separate batch of chips and having the same issue. I have since gained experience in IC manufacture and testing, knowing what I know now, this really isn't too suprising with NOS. FWIW I purchased a number of yamaha synths from ebay a couple months back and found only 1 of 5 pcs I purchased actually worked properly.

In IC manufacturing parts are practically always tested after assembly/encapsulation because there will always be defective parts during the assembly (wire bond and encapsulation) process. You have to ask yourself what happens to those parts which fail testing? If they're deemed unusable all you can really do is toss them in the trash. If some worker thought they might be able to pull them out of the trash to sell them on a black market of sorts chances are decent that they would have yanked em. One might wonder, well then why do some of them work? In testing there are always false failures, and additionaly a part can fail for reasons besides gross functionality. Perhaps those didn't meet all the timing specs, or they had too high of current consumption based on the spec etc. And the true failures aren't all going to fail the exact same way, they'll have varying issues which is exactly what you're seeing. More over you would probably expect that ~20-50% of the parts you 'throw away' are functional in practice. So that gives even more reason to pull them from the trash and have them end up in your hands 20 some years later. The person/company who sold them to you certainly didn't manufacture them, and they certainly didn't test them. So if whoever sold them to your distributor pulled them from the trash at some point, you'd have to expect what you're seeing.

They're just plain bad parts, not really worth your time and effort to investigate further IMO. Be happy with the working ones you have as proof that your testing apparatus works.

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If you're gonna play the Game Boy, you gotta learn to play it right. -Kenny Rogers


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PostPosted: Thu Jun 26, 2014 10:47 pm 
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And thats more than likely whats going on. Well, it was great while it lasted :wink:


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PostPosted: Tue Jan 10, 2017 2:04 am 
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I found a pinout of another MMC3 clone.
Its pin31 is named : DLYED phi2
How can I find out if this is the same pin for AX5202P (pin39)?


Attachments:
MMC3_DIP42.jpg
MMC3_DIP42.jpg [ 35.76 KiB | Viewed 252 times ]
AX5202P.png
AX5202P.png [ 8.99 KiB | Viewed 252 times ]
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PostPosted: Tue Jan 10, 2017 5:13 am 
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Delayed Phy2 = M2 (with delay added)

That new MMC3 clone you found the pinout for is the one which is usually marked "88" on top.


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PostPosted: Tue Jan 10, 2017 6:29 am 
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So it is the same as this?

lidnariq suggested adding a resistor and capacitor

lidnariq wrote:
Code:
card edge M2 --- 1k --- + --- PAL
                        |
                       33pF
                        |
                       gnd


What else it can be used for?


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PostPosted: Tue Jan 10, 2017 7:30 am 
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I think delayed M2 may be useful to prevent glitching the data written/read when accessing WRAM.

That resistor circuit is what Konami VRCxx cartridges use for delay when they have WRAM in them.


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PostPosted: Tue Jan 10, 2017 6:39 pm 
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What he said.

Delayed M2 is necessary to distinguish between writes to WRAM and writes to registers, because in a normal NES, M2 rises before /ROMSEL falls. Thus, there is a very brief moment that looks like a write to $0000-$7FFF when it's actually a write to $8000-$FFFF.


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