Anyone have CDX/Multimega internal pics?

[RobIvy64]

If any of you have any CDX/Multimega internal pics please post them here. I'd like to overclock it (what else is new) depending on if the CPU is housed in a custom IC or not. If it isn't then the procedure will be the same as the others. Thanks for your help guys!

-Rob

[GZeus]

I'm sure there are some out there, I know someone did a full-mobile modification to one.

[RobIvy64]

I'm sure there are some out there, I know someone did a full-mobile modification to one.

I'm sure someone's got some on their photobucket account or something. An extensive online search didn't yield any clear pics of the entire PCB top and bottom.

[blackevilweredragon]

im wondering if it is a custom IC..  the CDx is small, how much room could be there to fit two 68Ks?  (i know the Z80 is ultra small, probably the same from the genny 2)

[RobIvy64]

im wondering if it is a custom IC..  the CDx is small, how much room could be there to fit two 68Ks?  (i know the Z80 is ultra small, probably the same from the genny 2)

I would be surprised if the Z80 is not housed in a custom IC as well as the two 68Ks. The Genesis 3 and the later revisions of the PICO had 68Ks on a combo chip.

[kendrick]

The trick with the CDX is that there are two boards. Rather than consolidate all the components, Sega put in one board that provides the Megadrive functions and a separate board that provides the Mega CD functions. These two guys sit on top of each other, connected by thin and finicky wiring. If the CDX had taken off, Sega might have been able to take the hardware through another revision to consolidate all the gear on to one board.

I think it's safe to say that even if there are custom IC units on the board, most likely there are still two separate 68000 chips somewhere on there. I'm not willing to take my CDX units apart again, but I'm looking around for pictures too.

-KKC

[blackevilweredragon]

it probably is in a custom IC..  maybe that explains the compatibility problem with some Sega CD games?

[RobIvy64]

The trick with the CDX is that there are two boards. Rather than consolidate all the components, Sega put in one board that provides the Megadrive functions and a separate board that provides the Mega CD functions. These two guys sit on top of each other, connected by thin and finicky wiring. If the CDX had taken off, Sega might have been able to take the hardware through another revision to consolidate all the gear on to one board.

I think it's safe to say that even if there are custom IC units on the board, most likely there are still two separate 68000 chips somewhere on there. I'm not willing to take my CDX units apart again, but I'm looking around for pictures too.

-KKC

Thanks for the information. That is strange that the two are on two seperate boards.

I just got a CDX for $30 on eBay and should be in Saturday(mislabelled auction), so if no pictures turn up i'll bite the bullet and open her up.

Thanks for helping me guys.

[blackevilweredragon]

it's probably on two boards cause they couldn't get it to fit on 1 small board..  so instead of making the one board bigger, risking getting the unit wider or something like that, they pancaked another board on top of it (just making it slightly thicker, which it's already thin as it is)

[kendrick]

Forgot about this. SegaSonicFan, he of the portable CDX with built-in monitor and controller, posted some internal pics on a recent thread:

http://nfggames.com/forum/index.php?showto...t=0&#entry16607

The second picture clearly shows an MC68H000 chip next to one of the custom Sega ROM chips. So we have an independent processor on a small scale on at least one of the two boards. At this point, we challenge SSF to post more pictures. :)

-KKC

[blackevilweredragon]

and that chip would be on the Genesis board..

[RobIvy64]

and that chip would be on the Genesis board..

...and that would be what I would try to overclock since overclocking the SCD just doesn't work. Thanks for digging that up kendrick.

[blackevilweredragon]

good luck overclocking that thing..  it's very cramped, i don't even think there would be room for a crystal...

[GZeus]

Tray raising it by 25% increments.

[Guest]

good luck overclocking that thing..  it's very cramped, i don't even think there would be room for a crystal...

Fitting one in there wouldn't be an issue.

[RobIvy64]

good luck overclocking that thing..  it's very cramped, i don't even think there would be room for a crystal...

Fitting one in there wouldn't be an issue.

[RobIvy64]

Hmm looks like segasonicfan has already attempted an overclock on the CDX (note he has raised clock pin 15 and has a wire attached). It's a shame he probably wouldn't answer any PM I send him.

No big deal, i'll attempt this one myself and share the results with everyone.

[Segasonicfan]

hey, of course I would answer  I have checked and that is the right chip for overclocking, but it is pin 16 and not 15 (that's VCC).  Never hesitate to PM the segasonicfan  I also have pics of all the insides I will try to post up later (not sure I can get them off my camera with my adapter in LA though...:/)

-Segasonicfan

EDIT: Looks like I uploaded a couple before I left town ^_^ :
http://i18.photobucket.com/albums/b134/Seg...CDXlargetop.jpg
http://i18.photobucket.com/albums/b134/Seg...largebottom.jpg

[kendrick]

Huh. Was I wrong about the two boards then? It looks like the two 68000 chips are right there on the main board, side by side. They have slightly different model numbers though, so maybe there's more to this story. I'm sure after some light head trauma one of us would be able to figure out which one of these guys is the main Megadrive CPU.

-KKC

[blackevilweredragon]

well the CPU i saw was the Genesis one..  you can tell cause it's 8MHz..

[RobIvy64]

Thanks for the pics Segasonicfan! The two 68Ks are right next to each other, awesome. The one labelled MC68HC000FN8 is the mega drive CPU, and the one labelled MC68HC000FN12 is for the Sega CD.

What were your results when you overclocked it? Also, I heard you overclocked the saturn as well.

[Segasonicfan]

Yup, the MC68HC000FN8 is the cartridge CPU (8Mhz...well actually, 7.6Mhz) and the MC68HC000FN12 is for CDs (12Mhz).

I actually got side tracked working on some other projects right now so I haven't OCed it yet but I'm sure it will work fine with 10Mhz and 12Mhz xtals.  I just checked to make sure that it won't boot when that pin is disconnected (to make sure it's the clock input for the genny).

Also note, be DAMN careful desoldering it and using the trace for the original 7.6Mhz.  That is one of the only places to get the signal, screw up that solder pad and you will have to pull it from the output pin of the main processor (which=soldering hell).

and yup, I did overclock Saturns and sold em too  It's the exact same IC so you just lift pin 16 and input a new TTL clock signal (14Mhz worked just fine for Saturns).   You're welcome for the pics Rob, never be afraid to seek help from your friends on the forums

oh, and I'm suprised nobody noticed my little mod in the first pic...I put in a better chroma encoder (CXA2075 clone) ^_^

-Segasonicfan

[RobIvy64]

Yup, the MC68HC000FN8 is the cartridge CPU (8Mhz...well actually, 7.6Mhz) and the MC68HC000FN12 is for CDs (12Mhz).

I actually got side tracked working on some other projects right now so I haven't OCed it yet but I'm sure it will work fine with 10Mhz and 12Mhz xtals.  I just checked to make sure that it won't boot when that pin is disconnected (to make sure it's the clock input for the genny).

Also note, be DAMN careful desoldering it and using the trace for the original 7.6Mhz.  That is one of the only places to get the signal, screw up that solder pad and you will have to pull it from the output pin of the main processor (which=soldering hell).

and yup, I did overclock Saturns and sold em too   It's the exact same IC so you just lift pin 16 and input a new TTL clock signal (14Mhz worked just fine for Saturns).   You're welcome for the pics Rob, never be afraid to seek help from your friends on the forums

oh, and I'm suprised nobody noticed my little mod in the first pic...I put in a better chroma encoder (CXA2075 clone) ^_^

-Segasonicfan

Ahh OK i thought you had already overclocked it. On a side note, it is pin #15 that is the clock input pin. Pin 14 is VCC.



A switch will be necessary for that master 68K (genesis) because the Sega CD will not function even with the slightest overclock. I wouldn't anticipate too high of a clock speed since it has the same 315-5660 ASIC as the Nomad, which doesn't like the 68k overclock well.

As for the slave 68K (sega cd), don't even bother with that. For some reason the sega CD just will not boot with anything but the stock 12.5 MHz clock signal. I've tested anything from 12.8 MHz to 14.3 MHz on a model 1 and model 2 sega cd.


As for the Saturns, it sounds like you overclocked the 68K, which is only used as an audio controller. Any lag or performance issues are going to be totally dependant on the two Hitachi SH2s.

Did you overclock the 2 SH2's or the 68K?

[kendrick]

Not to get lost in a side topic, but isn't the function of the 68000 in the Saturn set by the software, the way it is in the Jaguar? I know that most games use it for audio, but as I recall the Shining Force titles used the 68000 for sprite scaling and animation functions.

-KKC, who wonders what happens if you put a 68010 in a Jaguar...

[RobIvy64]

Not in the saturn. It was strictly used as an audio controller just as the Z80 is used as an audio controller in the Genesis.

Overclocking the 68K would likely just cause a physical change in the speed and/or pitch of the audio.

[Segasonicfan]

ah yes, my mistake.  I confused it with the Saturn 68k which is pin 16.  

I have overclocked the Nomad before and I'm not sure what you mean about it not liking high OCs.  I sold a perfectly working OCed Nomad with 12Mhz and 10Mhz xtals (see here: http://www.neo-geo.com/forums/showthread.p...cation+service)

As far as the Saturn goes, you may be right about the 68k not truly overclocking the system, I did not test it enought to know (I never tried to OC the SH2s)  However, when I did OC the 68k to 14Mhz the audio remained the same so I'm not sure that it functions soley for audio...

-Segasonicfan

[RobIvy64]

ah yes, my mistake.  I confused it with the Saturn 68k which is pin 16. 

I have overclocked the Nomad before and I'm not sure what you mean about it not liking high OCs.  I sold a perfectly working OCed Nomad with 12Mhz and 10Mhz xtals (see here: http://www.neo-geo.com/forums/showthread.p...cation+service)

As far as the Saturn goes, you may be right about the 68k not truly overclocking the system, I did not test it enought to know (I never tried to OC the SH2s)  However, when I did OC the 68k to 14Mhz the audio remained the same so I'm not sure that it functions soley for audio...

-Segasonicfan

The saturn's 68K uses the same surface-mount package, so it's still pin 15.

Relatively speaking, 10 and 12 MHz isn't really a high overclock considering the Genesis model 1 can reach 24 MHz. 10 and 12 does smooth out most 2D games pretty well.

Devon Gallo and I are working to overclock the two SH2s to try and squeeze a little more performance out of it. I've overclocked the entire system with the two SH2s running at 40 MHz, but the video was out of sync, respectively. We know what clock signal it takes, we just need to find the right pin (the SH2 has a weird clock input-clock output system).

You may want to edit your sale thread and your website to reflect that it's not a true overclock since its the audio (and possibly I/O) controller you've overclocked and not the 2 CPUs. I hope you haven't sold too many.

[Segasonicfan]

foI didn't test it enough to see performance gains.  Just saw that it booted up and played.  its a different version of the 68k though and I remember it being a different pin than the gennys (pin 16).  Not really worth talking about though.

12Mhz is as high as most gennys will go with 100% compatibility rate.  So that's high enough OC for me

[RobIvy64]

foI didn't test it enough to see performance gains.  Just saw that it booted up and played.  its a different version of the 68k though and I remember it being a different pin than the gennys (pin 16).  Not really worth talking about though.

It's the same package. I'm not trying to argue I just don't want anyone to read this and try to overclock the audio controller by hooking their new clock to a ground. Thats why you didn't see any difference, you were still running off the original 11.3 MHz clock with your new clock hooked to a ground.

Heres a pic of my saturn's motherboard from wikipedia:

(note: 68K is located just right of the power connector)

[Segasonicfan]

jeezus...

I'm trying to stop people from reading what you're typing having NOT done the mod and messing up their boards.  I did the mod and it is a different surface chip, the MC68EC000FN12.  See below.



pin 16.

-Segasonicfan

[RobIvy64]

OK I stand corrected on the 68EC000 clock pin, but i've never tried to overclock the Saturn's audio controller before since there's no need to do so.

jeezus...

No need to get irate, i'm just trying to understand the facts.

[Segasonicfan]

I got irate because I had to take time out of my day to find the data sheet, copy the image and convert it to a paint document, upload it to photobucket and post it here because you wouldn't back down of the issue.

and like I said I don't think you are correct about it only being used for audio as when it is overclocked the audio speed does not change.  I could be wrong about this since I have not seen full documentation on the Saturn but I would like to know how why you think it is soley an audio controller.  

I'm just here like you to try to help people out so please, when someone has done a mod that you haven't just try to take their word for it.

-Segasonicfan

[blackevilweredragon]

even if it was an audio only CPU, it wouldn't change the speed of the music..  doesn't it get it's timing from a RTC?  cause if so, it just means it gets done crunching numbers quicker..

[Segasonicfan]

even if it was an audio only CPU, it wouldn't change the speed of the music.. doesn't it get it's timing from a RTC? cause if so, it just means it gets done crunching numbers quicker..

Good point.  It may be just an audio CPU I'm just curious how Rob knows (I don't know too much about the Saturn hardware).  Any schematics out there online?  I'd also like to help with the SH2 OCing when I get done with some other projects.

-Segasonicfan

[RobIvy64]

I got irate because I had to take time out of my day to find the data sheet, copy the image and convert it to a paint document, upload it to photobucket and post it here because you wouldn't back down of the issue.

and like I said I don't think you are correct about it only being used for audio as when it is overclocked the audio speed does not change.  I could be wrong about this since I have not seen full documentation on the Saturn but I would like to know how why you think it is soley an audio controller. 

I'm just here like you to try to help people out so please, when someone has done a mod that you haven't just try to take their word for it.

-Segasonicfan

Even if myself, and everyone else were wrong about it being an audio controller like the Z80 is in the Genesis, it's still not the CPU, and overclocking it and selling it as an "Overclocked Saturn" is wrong in my opinion. You can't honestly tell me as an experienced modder that the two SH2s aren't directly effecting performance and that the 68K tackles the load.

Check out the schematics, and check out the position of the 68K on the board (right next to the Yamaha  SP). It all adds up.

I don't want someone overclocking the 68K thinking they are overclocking a Saturn.

[blackevilweredragon]

The Z80 was near the YM2612, but it could be allowed for game logic too..

[Segasonicfan]

you do you don't even have any proof that its an audio controller? only that it's near the Yamaha chip?

I sold my Saturns as OCed because I thought they were, you are the first person to bring to my attention the possibility that the 68k is only used for audio.  and technically speaking i did still overclock them, it was not like I was trying to rip people off.  That is a pretty rude thing for you to insinuate.

-Segasonicfan

[RobIvy64]

The Z80 could not be used for any "game logic" besides audio and master system compatibility (using the converter).

you do you don't even have any proof that its an audio controller?

Saturn Schematics

CLick on the sound CPU, the lines attached to "MPU" are connected to the 68K.

Also, there's schematics for the SH2's if you are wanting to try it yourself. If you thought they were overclocked then you can't help it, but if you continued to sell them as overclocked that wouldn't be cool. Technically, yes, a component is overclocked, but when someone is looking to purchase an overclocked system they are looking for a performance gain which this doesn't deliver.

[blackevilweredragon]

Then how did F-22 use the Z80, along with the 68K, to run the game logic?

[RobIvy64]

Then how did F-22 use the Z80, along with the 68K, to run the game logic?

What are you talking about?