Great comparison between Mega Drive - Genesis RGB output.

[bateman82]

I've discovered this great article recently:

https://medium.com/rgb-inside/comparing ... d3703270ba

It's a great work done with precision (not too far from Fudoh incredibly high standard) and love, here's the (quite incredibile) results:

"Ranking of RGB quality of our tests
1) X’Eye from JVC
2) Mega Jet
3) Mega Drive III from Tec Toy
4) CDX from Tec Toy (we tested the Tec Toy model, but any CDX would apply here)
5) 32X
We hope the information here will help you choose the best Mega Drive/Genesis to use in your setup. Please notice that these results were reached in a top of the line setup, and of course even different units of the same console model can produce different results. In addition, the assessment here was subjective, from observations and comparisons using the TV screen itself and the screens captured. For those who are not demanding enough to seek the most expensive models, you can easily go for the Sega Genesis Model 1 or Mega Drive III and you will have good results too!!!"

So the Japanese Model 1 High Definition has terrible jailbars and the X'eye the best clarity

I know that there is a thread on Sega-16 http://www.sega-16.com/forum/showthread ... m-bad-ones but it is incredibly long, not updated in the first-main page (only composite).

I think it's worth a mention in one of the RetroRGB podcast (great work man!).

[tjstogy]

Thanks- interesting article and super in depth. I was surprised he didn't throw an RGB bypass modded console in there- I bet that would've come out to be the "best"

[Syntax]

Guy has way too much spare time.
Why anyone would review a Mega Drive 3 is beyond me. Such a hack of a console with poor compatibility.

Best cheapest option by far is RGB bypass amp which he never even touched on.

Pretty pictures tho..

[FinalBaton]

I disagree with them on the sound : an X'eye sounds super clean, yes, but it sounds a bit clinical (not as involving, as enjoyable)compared to a model 1 VA 2 or VA3-VA6.5. The filtering is just not as musical...

[ApolloBoy]

Guy has way too much spare time.Why anyone would review a Mega Drive 3 is beyond me. Such a hack of a console with poor compatibility..

To be honest it's actually not all that bad if you just want to play Genesis/MD carts, granted it doesn't have stereo audio but a Mega Amp mod sorts that out.

[BuckoA51]

Good article but would have been better if he'd actually opened the Megadrives and checked what motherboard revision it was.

[Fudoh]

nice info indeed.

I'm wondering why the Genesis exhibits visibly less jail bars than the MD1. On the VDP the clock signal is obviously still located next to the blue color channel. Did Sega change the board, so the two signals are no longer running next to each other before they reach the video encoder ??

[kamiboy]

Bu- bu- but what about the @games Mega Drive? The choice of the true connoisseur.

[FBX]

Honestly, once I severed the trace to pin 6 on the CXA chip, the jail bars were 100% gone on my Hi-Def model 1 Genesis. The picture is absolutely perfect on it.

Edit: I see they did try one with the trace severed. They said it was quite good, but on mine, it came out frikken amazing. Might be different revision or something.

[FinalBaton]

Honestly, once I severed the trace to pin 6 on the CXA chip, the jail bars were 100% gone on my Hi-Def model 1 Genesis. The picture is absolutely perfect on it.

Edit: I see they did try one with the trace severed. They said it was quite good, but on mine, it came out frikken amazing. Might be different revision or something.

I also have no jailbars whatsoever on my model 1 VA2 (see my captures from hardware on YT). I lifted pin 50 on the VDP chip but to be honest I'm not even sure there were jailbars in the picture before I performed that ¯\_(ツ)_/¯

Maybe different revisions of the model 1 have some jailbars ones while others don't?
(could the way the traces are laid out differently on different mobo revisions have an effect on this, as Fudoh said? because they all have the Sony CXA1145 encoder chip)

[FBX]

I lifted pin 50 on the VDP chip but to be honest I'm not even sure there were jailbars in the picture before I performed that

On mine, it was a night and day difference. Before severing the trace: Massive jail bars. After severing the trace: Crystal clear RGB picture.

[pyroman512]

I have a model 1 without HD graphics logo. It is the one that has the space for that port on the back. According to that thread on RetroRGB it still has good sound. I haven't tested that one on my 4K tv to see how the jailbars would look. But it looks fine on the CRT I keep in my backyard man cave.

I keep a genesis II on my main setup and maybe the framemeister is compensating for it but I have noticed no issues on it with video or sound. I think I got very lucky with this revision. Of course I don't have the eyes FBX has but I'm fairly happy with it. I think I'll still do a bypass once they are readily available.

[Ryoandr]

I have found with MD1 that, the instant you have a subcarrier you'll get jailbars. Be it with composite as sync, or with S-video modding. But, if you use a cleaner signal as sync such as luma as sync, composite sync from CXA1145 pin 11 or sync from the VDP, you'll have no jailbars (or extremely little), even with subcarrier clock line still connected between VDP and CXA1145.
Jailbars were never a problem with french MD1s because they're wired a bit differently, there's no Y/C mixing and composite out components and AVOut composite pin is wired to CXA1145 pin 11 with a jumper wire. But when I tried to s-video mod I got jailbars. And of course the cable used has it's importance, a long and/or poor shielded cable will amplify jailbars, sometime dramatically.

I don't know if the CXA is at fault but it seems it really doesn't like having some kind of load related to the subcarrier. I have an MD2 with a Fujitsu MB3514 that is S-video modded and with the right cable it's pretty much crystal clear, even rivaling RGB.

[FBX]

I don't know if the CXA is at fault but it seems it really doesn't like having some kind of load related to the subcarrier.

On mine it was a physical property of the CXA causing the jail bars. The blue channel of the RGB lines is situated right next to the composite encoding process inside the CXA chip. That composite video processing was physically coupling over into the blue line of the RGB signal. So by severing the trace to pin 6, the processing is cut off before it can begin. Hence, the instant clearing of the RGB image after cutting that trace.

I remember getting into a heated argument about this with some modder on Facebook that claimed in all his 20 years of working on Genesis consoles, he had NEVER heard of that issue, and as such, I must be either wrong or lying. He kept arguing and arguing, and would refuse to watch videos I linked to him from other modders that were fully aware of the issue. This was just so he could keep arguing the point. I'm pretty well headstrong as others here know, but eventually I figure it out and get it right. This guy wouldn't hear of it no matter what proof was brought to the table. He eventually got spiteful and reported my name as being false to Facebook, and I had to eat a 24 hour suspension while I proved my name was legit.

[bateman82]

I disagree with them on the sound : an X'eye sounds super clean, yes, but it sounds a bit clinical (not as involving, as enjoyable)compared to a model 1 VA 2 or VA3-VA6.5. The filtering is just not as musical...

I've only got a pal Mega Drive model 1 High Definition, but I like how the Jvc unit sounds (not by any means filtered like, for example, the FM sound on the Everdrive or Power Base FM, here's the video:
https://www.youtube.com/watch?v=ayKxnrYCpPI&t=34s)

Sound is a lot more a personal preference than the video quality, so it's hard to declare a true winner.

You can hear the difference in this video too:
https://www.youtube.com/watch?v=O-KsaGBUVz4&t=247s

In any case I've got an X'eye coming so I can test it.

Good article but would have been better if he'd actually opened the Megadrives and checked what motherboard revision it was.

You're right, it's a pity.

[FinalBaton]

Sound is a lot more a personal preference than the video quality, so it's hard to declare a true winner.

In theory, yes. But the revisions I mentionned were around when developpers made games, while the JVC was not(or was for the very late part of game development cycle of the console), so it's hard for me to be convinced that the JVC's EQing of the soundchip is "how Genesis games were intended to sound like". *is skeptical*

Anyway, were not talking a HUGE difference here, the JVC sounds great either way!

In any case I've got an X'eye coming so I can test it.

Nice! I've always wanted an X'eye. It's a away cool machine. Hopefully I'll find one at a decent price in the local classified at some point

[AndehX]

My Japanese Model 1 has really bad Jailbars and lifting pin 6 on the CXA did absolutely nothing. I NEED Rene's RGB triple bypass! Someone start producing them!!

[Einzelherz]

These kinds of tests always irk me. How many of each identical mobo model presented were tested? Were they all recapped? Did they all use the same cabling? Etc.

Because in this hobby group one person makes a claim and more often than not it becomes repeated as gospel and just argh.

[ApolloBoy]

My Japanese Model 1 has really bad Jailbars and lifting pin 6 on the CXA did absolutely nothing. I NEED Rene's RGB triple bypass! Someone start producing them!!

You can try lifting pin 50 of the VDP (or at least cutting the trace to it) which is the color subcarrier signal. It's a little tricky but once you do it, the blue jailbars disappear and you get a very nice picture.

[FBX]

My Japanese Model 1 has really bad Jailbars and lifting pin 6 on the CXA did absolutely nothing. I NEED Rene's RGB triple bypass! Someone start producing them!!

You can try lifting pin 50 of the VDP (or at least cutting the trace to it) which is the color subcarrier signal. It's a little tricky but once you do it, the blue jailbars disappear and you get a very nice picture.

That's the same trace as pin 6 of the CXA.

[FinalBaton]

These kinds of tests always irk me. How many of each identical mobo model presented were tested? Were they all recapped? Did they all use the same cabling? Etc.

Because in this hobby group one person makes a claim and more often than not it becomes repeated as gospel and just argh.

This is a good point

It's still cool that these people did this test. but yeah it could have been more rigourous

[ApolloBoy]

My Japanese Model 1 has really bad Jailbars and lifting pin 6 on the CXA did absolutely nothing. I NEED Rene's RGB triple bypass! Someone start producing them!!

You can try lifting pin 50 of the VDP (or at least cutting the trace to it) which is the color subcarrier signal. It's a little tricky but once you do it, the blue jailbars disappear and you get a very nice picture.

That's the same trace as pin 6 of the CXA.

True, but I've heard cutting pin 6 doesn't always work (as you probably saw in the post I quoted!) so it's better to cut it off right at the source, no?

[FinalBaton]

True, but I've heard cutting pin 6 doesn't always work (as you probably saw in the post I quoted!) so it's better to cut it off right at the source, no?

It does make more sense (at least to me) to cut it at the source, indeed

[FBX]

True, but I've heard cutting pin 6 doesn't always work (as you probably saw in the post I quoted!) so it's better to cut it off right at the source, no?

It does make more sense (at least to me) to cut it at the source, indeed

No because the coupling is happening inside the CXA chip, so it doesn't matter where you cut the trace. If it doesn't work when you lift pin 6 for example, then the CXA is not at fault in that case.

[FBX]

I made an image of the schematic of the CXA chip so you can see the physical location of where the coupling is happening:



As you can see, it doesn't matter where you cut the trace. Just so long as that oscillator can't receive the signal, so it won't couple into the blue channel.

[Ryoandr]

Anyone decaped a CXA1145 ? Would be nice to see the exact root of the problem.

[FBX]

Anyone decaped a CXA1145 ? Would be nice to see the exact root of the problem.

It's already been documented, and you can see it in the image I posted. The oscillator is physically right next to the blue line, so it couples over to it.

[TestType]

I think it's worth a mention in one of the RetroRGB podcast (great work man!).

Actually Bob already covered this on the podcast back in July: https://youtu.be/XWCIj1q_Kq0?t=609

It's a very interesting comparison indeed, but I do agree with others that I wish it was a little bit more thorough and had more information about the models beyond surface observations.
Still, it was enough for me to cancel the Japanese Mega Drive 1 that I was in the process of buying when I saw this in July.

[Ikaruga11]

Which model of the Genesis has the best picture/sound?

[FBX]

Which model of the Genesis has the best picture/sound?

I can only speak of ones I've seen of course, but I've got zero complaints about the sound and RGB PQ on mine (after I severed the trace to pin 6 of the CXA of course). Mine is an original Hi-Def with expansion EXT intact, and the board revision is a VA3. VA2 is the very earliest, and have the best sound provided the game doesn't drive the sound too loud, if the game is too loud, the sound gets pretty awful. On my VA3, the sound is a little more filtered, and the gain has been lowered to prevent games from overloading the sound into a static mess.