Questions about the VA4 Genesis/Mega Drive model 2

[Xaranar]

So, by sheer luck I've managed to get a hold of a VA4 model 2 Mega Drive; a PAL one no less, I didn't think anything beyond the VA1.8 even existed in the PAL region, but I am wrong it seems. Now, I am to understand that being the final board revision of the console, Sega condensed the entire system into a GOAC - mine has the Sega 315-5960 ASIC, which means it doesn't have a separate CPU or anything. Now, some people tout this board revision as the very best stock version of the model 2, but others have noted some incompatibilities with it and some 32X games, probably most significantly Knuckles Chaotix. Does anyone have any experience with this board revision in particular? I'm going to basically retrofit it into a US NTSC board by removing the jumpers that set the region so they both pull up 5V, and replace the master oscillator with a 53.6931MHz one, but is there any truth to the Knuckles Chaotix thing? Also, because everything has been condensed into one ASIC, is it even possible to overclock this revision like you can with those that have a separate Motorolla CPU?

Edit: The board I have is also somewhat rarer I believe, as it doesn't have the Sony encoder as the spec sheet says it should, it has the Rohm BH7236AF.

Cheers all!

[Xyga]

Yeah it's supposed to be the best MD2 revision, in particular for sound if I remember correctly.

Missed two opportunities to get one in like 10 years, never seen another one ever.

Does it have the damned jailbars on RGB as well ? That's really the main problem with MD2's, and apparently lifting a single pin like on the MD1's is not an option.

[Xaranar]

VA3 and VA4 are identical in terms of sound, but yes it’s by far the best MD2 revision for sound, improved upon by the Mega Amp. I’ve never had a problem with jail bars on an MD2, only on the MD1, and cutting the composite video trace made no difference at all. Because it is a GOAC, though, similar to how the SNES Jr is a single chip revision, it makes me wonder if there are quirks.

[SCARTicus]

I have either a VA3 or a VA4 (don't remember) and it is great. The sound is fantastic. I don't feel a need for a MegaAmp, and it is the best mate for an SCD2 (MegaAmp breaks SCD compatibility).

I have never noticed anything odd or broken as far as compatibility goes. I do not have a 32X, though.

They're not rare, good-sound model 2s. You can usually tell without opening them by looking through the vent holes in the bottom of the console. The good ones have half or three-quarter cut boards, and the bad ones are usually full size, IIRC. That's how I found mine.

I have never heard about a Genny with a Rohm encoder. Maybe that was a PAL only thing?

Anyway, cool find, but it seems to me that it would be easier to just get an NTSC model 2 VA3/4. If you ask an ebay seller, they will usually check the console for you.

I hope someone else can chime in on the Chaotix thing; that is something that I would be very interested in hearing more about. I love the model 2.

[FinalBaton]

Also hoping to pick one up cheap, for matching with a Sega CD model 2. Already have a model 1 genesis + model 1 Sega CD combo, but I want a model 2 one too.

[Xyga]

It's on sega-16 that I've read about slight differences between VA3 and VA4 for sound. Anyway yeah they're both good.

They might not be rare where you are but in my country they sure are, vA1.8 are all I've ever seen besides those two VA4's.

[Xaranar]

After testing mine out, I'm disappointed. Maybe I'm spoiled by the Mega Amp, because it sounds just amazing, but the VA4 sounds very weak and muffled compared to it. I don't know how the Mega Amp breaks Sega CD compatibility, I've never had a single issue with running the SCD through it, mine works great. Also, the RGB video output is some of the noisiest I have ever seen, perhaps even noisier than the VA0. I've never come across a 2 or 2.3, but as it stands, I'm of the opinion that a 1 or 1.8 are the best, with a Mega Amp installed.

[Xyga]

RGB quality (save for the jailbars apparently since not everyone has had the same experience) should be consistent accross revisions, but if you're using an original MD2 scart cable those are notoriously terrible and the cause for the noise.

I have two that I'm using with two VA1.8, and I had to mod both cables radically, cutting two traces and rerouting 5V.
The signal's now completely clean and noise-free.

There are tutorials around showing the traces to cut, but not how where to bridge 5V (it's facultative anyway)

[Xaranar]

You're right, it *should* be consistent, but it isn't. I use the same cable for all my tests, which is an individually shielded SCART cable from Retro Gaming Cables, and I have found the VA0 to be the worst, followed by the VA4, then the VA1 and 1.8 which look amazing by comparison.