Garbled sprites on FDS

[Zycrow]

My suggestion is, if you have any of the games on this list (which contains all Famicom carts with CHR RAM) is to test one of those games and see if you also have corruption. The only thing to throw a wrench into that line of reasoning is that your FC worked with koitsu's RAM adapter but not your own. That should rule out the FC itself, except for the fact that your RAM adapter worked on koitsu's FCs but not your own.

Maybe it's an issue of dodgy pins on both your FC and your RAM adapter, but the pins aren't dodgy enough to fail when used with other hardware, but when used together you have a pin not making a connection at all. Sort of like how the Guitar Hero 3 guitars with removable necks inevitably get dodgy connector pins, but swapping necks can cause different behavior from the pins being worn differently.

I took a cursory look over that list and I have at least one game on it (Rainbow Islands) and haven't experienced corruption with it. At the moment I don't think I have any untested games for my FC, and I haven't experienced anything remotely like what I have on the FDS.

Also, did you try your FDS + my FDS AC adapter + your FDS RAM adapter? Part of me ponders voltage, since you're normally driving your FDS off of C batteries.

Another test would involve $$, and that'd be getting yourself another Famicom to see if the problem goes away.

I will do some power-related tests tomorrow and see what I get.
I really don't want to have to buy another Famicom, especially since I'd need an AV or an AV modded one to reliably get it to work on the TV I use.

Part of me thinks it's got something to do with the edge connector contacts between the FDS RAM adapter and the Famicom, which could explain why Zycrow's FDS RAM adapter worked just fine on my Famicom AV. I should have tried wiggling it or applying more pressure to it while it was inserted. Zycrow, you might try that -- just try shifting around or applying a bit of pressure to your FDS RAM adapter while attached to your system (doesn't matter whose FDS from the sound of it).

Since the issue reminded me of some of the graphical garbling I used to get on my NES when I was playing with a poor pin connection, I did try this a bit before I got on the forums, and it didn't seem to make a difference. Will try it again, though.

P.S. -- Zycrow, there was something I noticed about your FDS RAM adapter -- one of the screws in one of the corners looked like it wasn't screwed in all the way. I didn't touch this/change it at all, but if you didn't open it then someone in the past may have, indicating someone may have tried to repair or fix something previously. Totally speculative, but thought I'd mention it.

This was probably just from when I opened it up earlier to take a look at the chips inside. The garbling was the same before and after I did this (and I probably just failed to screw that last screw in all the way, yeah.)

So, if you exchange your RAM adapter with Koitsu's, you'll both end up with fully working FDSes, no ? Although it doesn't answer to why a particular combination doesn't work, honestly this is really crazy.

Getting a new Famicom or FDS is expensive, but plain RAM Adapters are very common and cheap on EBay (or at least were last time I checked), so it shouldn't be too hard to have a solid stock of a few adapters if there is a need to.

Exchanging our RAM adapters is my preferred course of action. I'd be willing to trade back if mine starting malfunctioning with Koitsu's system, even. But that's entirely up to Koitsu. I'm just really happy that you guys have been willing to try to help me out on this at all.

[koitsu]

Please try the power-related tests (AC adapter vs. C batteries).

There's something that just doesn't sit well with me about this situation in general -- it's probably the OCD part of me wanting an actual explanation for what is going on, rather than just swapping FDS RAM adapters and saying all is well. I worry that if we swap, fast forward a few weeks/months (or maybe even a year), and suddenly "something odd starts happening", I'm going to be kinda ticked off. I only say this because I think I've spent something like US$500+ on Famicom and FDS stuff to get a working/reliable setup and I'm a bit reluctant to change what I know works when we don't have a completely definitive technical explanation for what's going on. I'd really have expected your FDS RAM adapter to malfunction on my stuff... :/

I have an alternate/different solution that will probably work (if not we're in no different shape than now), but it will take me some time to get it to you (roughly 2-3 weeks). You can use my stuff in the meantime; no rush to ship anything back yet.

[lidnariq]

But does it really take extra time in the PPU to flip a sprite horizontally? I thought it'd be just a mux between the flipped version of the sliver and the not-flipped version, selected by the H bit of the sprite's attribute 2. Vertical flip is just an XOR gate between the line-within-sprite and the V bit.

Sorry for the wild tangent, but I felt this overwhelming need to find where this was in Visual2C02.

Nodes 1860 and 1842 are the gating signals that select horizontal mirroring bits or not respectively, and they allow conduction from e.g. _db0 or _db7 to later processing logic (and ultimately spr0_l0 and spr0_h0). They're the two halves of an SR latch, gated on /spr_loadFlag NOR pclk1, and ultimately fed from spr_d6.

So, yeah, that random hypothesis neither made sense (in hindsight) nor has anything to do with the actual instantiation.

[Zycrow]

Please try the power-related tests (AC adapter vs. C batteries).

There's something that just doesn't sit well with me about this situation in general -- it's probably the OCD part of me wanting an actual explanation for what is going on, rather than just swapping FDS RAM adapters and saying all is well. I worry that if we swap, fast forward a few weeks/months (or maybe even a year), and suddenly "something odd starts happening", I'm going to be kinda ticked off. I only say this because I think I've spent something like US$500+ on Famicom and FDS stuff to get a working/reliable setup and I'm a bit reluctant to change what I know works when we don't have a completely definitive technical explanation for what's going on. I'd really have expected your FDS RAM adapter to malfunction on my stuff... :/

I have an alternate/different solution that will probably work (if not we're in no different shape than now), but it will take me some time to get it to you (roughly 2-3 weeks). You can use my stuff in the meantime; no rush to ship anything back yet.

Perfectly fine and understandable. Meanwhile I'll try some of those other tests.

[Zycrow]

OK! I tried a couple other things, but the results weren't terribly surprising.

First, I used my FDS and RAM adapter and powered it on with Koitsu's AC adapter. The results were garbling, as usual. I then used this same configuration switching to Koitsu's RAM adapter, and the garbling was gone.

I also moved my RAM adapter slightly in and out of the Famicom while a game was on. This would usually cause the game to freeze or the whole screen to go into a sort of plaid glitch-out, but I didn't see a visible effect on the sprites. (I performed this test with Super Mario Bros. 2, where the garbling is easiest to see from the get-go.)

If you guys would like for me to try some other tests, I'm happy to, and Koitsu, just tell me when you'd like me to ship your stuff back to you and I'll do so. Once again I'm super appreciative of all of your help.

[koitsu]

Bummer, was hoping as a last resort that the AC adapter might rectify something. Oh well, at least we've ruled some bits/pieces out.

I'll be sending you something (it's a surprise) in a couple weeks to see if that solves your dilemma. If so (crossing my fingers!), keep it (free of charge -- let's just say knowing people who live in Japan comes in quite handy). After that, yes, please send me back my FDS + FDS RAM adapter + AC adapter + box + Kid Icarus disk. :-)

[Pokun]

Have you tried holding START and SELECT on controller I while powering on with the RAM adapter to start the RAM test? I doubt anything will come out of it but it's worth a shot.

@Bregalad -- ahh okay. (See, EE isn't my thing... heh )
For an unrelated yet equally bizarre-as-hell issue with someone's FDS RAM adapter, check out this thread at Famicomworld. It starts getting interesting (and into specific models of chips in the FDS RAM adapter that are glitchy/buggy in some way?) at the 2nd page. Ignore the crap on page 3 onward -- just adolescents fighting over nonsense -- although there is an interesting tidbit on page 5 (talking about FDS RAM adapters with two different kinds of CHR RAM chips I think).

I remember that thread. It was a heated discussion and it looks like some of the posts have been deleted since then. Anyway that incident is what made people to start suspecting CHR RAM chips to be faulty and is why I thought this was something similar. It has been researched in this thread http://www.famicomworld.com/forum/index ... pic=8512.0 but in the end no concrete results have yet to appear.

[koitsu]

Have you tried holding START and SELECT on controller I while powering on with the RAM adapter to start the RAM test? I doubt anything will come out of it but it's worth a shot.

I had no idea there was such a self-test. Hidden features...! :P

[Pokun]

There's also a hidden message on newer BIOS revisions. After starting up with the self-test, hold RIGHT and A buttons and Takao Sawano's hidden message appears. Doesn't work on mine because I have a RAM adapter with the older BIOS.

[lidnariq]

newer BIOS revisions

Plural? I only knew of "original" and "Twin Famicom"...

[Pokun]

I don't know how many versions of the BIOS there is, but counting the Twin Famicom there are at least 3 versions.
I have the older 7201 FDS drive and the included RAM Adapter also seems to have the older BIOS as that hidden message doesn't appear, while on my friend's RAM Adapter (he has the newer 3206 drive) it does appear. I've tried the trick on both RAM Adapters myself.

It should work on the Twin Famicom BIOS version as well, I think the hidden message says what BIOS build it is.

[Bregalad]

Considering there is no jump table for BIOS calls, the room for revising the BIOS is extremely thin. How does both versions differ (if those 2 versions are actually confirmed to exist) ?

I should definitely try to dump mine with TapeDump.

[Pokun]

The only difference I know of is that the hidden message doesn't exist on the older version(s). Maybe I should try dumping my RAM Adapter since the newer BIOS is already dumped. I have no experience in dumping though.

[Zycrow]

OK! It's time for a new chapter in Zycrow's Weird FDS Problems.

Today I received in the mail another package from the endlessly generous Koitsu, and this time it was a third RAM adapter (we will call it subject "C").

The bad news is that subject C did not solve our problems. In fact, to make things even stranger, subject C is actually less reliable than my original adapter (we'll call it subject A).

So far, I've tried all of my games with subject C and my own FDS. I may try some other combinations before I ship all of Koitsu's stuff back to him. The results:

Super Mario Bros. 2: Game freezes on the title screen; sometimes the screen is blank or completely glitched out. Mario's sprite is garbled like with subject A, but not quite as much.
Moero Twin Bee: Garbling on the sprites during the intro sequence; game freezes afterward.
Doki Doki Panic: Game freezes immediately.
Metroid: Game freezes after title screen.
Palutena no Kagami (my copy): This was the only game that actually loaded all the way. Pit's sprite was garbled, but not as badly as on subject A, and there was some other graphical glitchiness here and there.

I have not tried out Koitsu's copy of Palutena no Kagami yet.

So, wow! What a weird situation. I think what I'm gonna have to do is just hunt down RAM adapters until I get one that works.

EDIT: I should note that before and during my testing, I did several rounds of cleaning on subject C's connectors, as well as my Famicom's connectors, just for good measure. This appeared to have a small effect on SMB2, though I was never able to get past the title screen there.

[koitsu]

The fact there's now two suspect FDS RAM adapters involved (one of which worked fine on my own setup here) seems to imply the issue may in fact be with the Famicom, possibly the cartridge/edge connector not making full/good contact with all FDS RAM adapters.

I can't confirm or deny that the FDS RAM adapter we call "C" works, because my FDS setup is with you. :-)

So if there was something to try replacing, I would suggest starting with a Famicom. I know your Famicom is modded or something to work on your setup (video-related? Maybe RGB mod? Or component mod?), but it's starting to sound to me like you just have a crappy cartridge slot on your Famicom that works "mostly well" with carts but possibly used FDS RAM adapters have a slightly different edge connector thickness or something and it's just enough to make your Famicom wig out. I've seen this myself on my old (now-given-away) original Famicom whose cartridge connector was quite worn -- slightly touching a cart would result in graphical garbling. It's the best guess I have at this point, and it's all speculative on my part.

This is partially why I wish I had sent you my Famicom AV as well, but to ship all that in one box would have been quite a lot (more than I already paid). Otherwise I do not have a spare Famicom or Famicom AV to send you. :(

I also don't mod anything I own (nor do I buy modded stuff) solely because I don't trust the modifications. For all I know one of those bazillion mods causes some kind of weird voltage or electrical problem that manifests itself in rare edge cases. I'm not an EE guy so again all this is speculative. This is one of those things where someone familiar with all that needs to be present physically in person to actually troubleshoot what is going on, otherwise all we're gonna end up doing is just spending money on products + shipping until "we find a combo that works" (when aside from clone incompatibility, all this stuff should "just work").

EDIT: I should note *prior* to sending you FDS RAM adapter "C", I cleaned the edge connectors using the same methodology I've cleaned all my NES and Famicom cartridges with (glass top cleaner followed by post-clean-up using ~80% isopropyl alcohol).