9MHz Overclock

Discussion in 'Mega Everdrive / Everdrive MD' started by lnx64, Dec 26, 2012.

  1. lnx64

    lnx64 Robust Member

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    I was curious, will the Everdrive boot on a Genesis overclocked to 9MHz? Technically not overclocked since the CPU in my Genesis technically was made for 12MHz (military version of the 68000 in a nice hardened ceramic package).

    If not, what if I run it at 8MHz? It's a small overclock to the Genesis, but sure beats the odd 7 and a half MHz SEGA chose, which is still an under clock to what the original was rated for anyway.
     
  2. APE

    APE Site Supporter 2015

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    You're misinterpreting a lot of details there.

    First off, the 68ks were designed to run at a variety of frequencies; there is no "technically" about it. The Genesis runs just fine at 7.67 MHz and games were designed around that. There is nothing deficient about it and it is not considered an "underclock". You can get 68ks that run at 20mhz but that doesn't make it an overclocked CPU. Unless you've swapped out the 68k that was originally in your Genesis for this mil spec model I highly doubt it is the same part as mil spec usually costs considerably more than a plastic packaging. I could be wrong but I don't see why SEGA would use military grade parts in consumer hardware. Running the poor thing at 12mhz is too much for the rest of the system to handle properly and you get graphical and audio corruption.

    That said I have run a 10mhz crystal inside a JVC X'EYE without any noticeable problems even in games that are finicky about clock rate. Unless the Everdrive is even pickier it should likely run but the whole point of using a HALT switch is so that you could boot a game with the Everdrive and switch frequencies so that the Everdrive (hopefully) won't mind.
     
  3. lnx64

    lnx64 Robust Member

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    I did swap out the CPU. But these CPU's are rated in their part numbers. The MC68000P8 used in the Genesis means the CPU is rated for 8MHz. It can of course be under clocked, but Motorola rated it for 8MHz.

    My CPU uses a custom part number, but Motorola says it's basically a special version of the MC68000L12, which is rated for 12MHz use.

    I was hoping to NOT use a HALT switch, and basically find a speed that works with everything without issue.

    The only reason SEGA chose the speed they did for the 68k, was to keep costs down, and share the clock used for the YM2612, since it's close enough.
     
  4. sonicdude10

    sonicdude10 So long AG and thanks for all the fish!

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    KRIKzz has said he doesn't support overclocked systems for his Everdrive line.

    SO...
     
  5. lnx64

    lnx64 Robust Member

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    Well supporting it is one thing.

    The question is, does it work though? Sonic 2 doesn't support overclocks, but it can work. ;)
     
  6. MottZilla

    MottZilla Champion of the Forum

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    You can try it and find out. Chances are no one has tried it here and that it will work if you use the standard scheme of starting in the normal clock frequency and after loading the game switching to the higher frequency. As others stated there is no support offered for modded or cloned systems. The higher frequency could cause problems with SD card access. Really I don't see what's so bad about doing the normal method of having a standard and high speed mode and utilizing the Halt feature to switch.
     
  7. Barone

    Barone Active Member

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    This is not true in all cases. Some Genesis/Mega Drive revisions of the model 1, like the VA5/VA6, do handle the 12 MHz overclock just as most of the models handle the 10 MHz one.
    Here's a video from a friend of mine using the same overclock circuit that I use:

    http://www.youtube.com/watch?v=66NayvXWhkY


    Exactly, there is no support and we should not blame KRIKzz for any possible problem/issue involving a modified/overclocked/clone Genesis/Mega Drive.
    However, just as an unofficial piece of info and don't blame me or anybody else for whatever problem you may have using such info: you won't be able to boot your system overclocked and use your Everdrive MD if it has a firmware v9 or older. All I say is just based in my friend and mine's experience, so it's not a general rule and NEVER something to go bust KRIKzz balls. Anyway, I boot my 12 MHz overclocked JP MD and use the Everdrive MD with no problems. The halt switch is always a must IMO since you may want to check the overclock "improvements" in games on the fly or just to make it easy to debug your circuit when you're testing it.

    With that said, again, NEVER ask for KRIKzz support about any overclock related stuff and don't blame anyone here if you, for an example, end up exploding your Genesis and burning your house down due to the overclock.
    Also, we had already addressed all these questions in Sega-16 but you could have asked it there anyway, lnx64/evildragon. ;)
     
    Last edited: Dec 27, 2012
  8. KRIKzz

    KRIKzz Well Known Member

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    I definately know that early vesion of edmd does not work with overclocked systems, but i don't know what about mega-ed and current version of edmd. I did never tested my carts on overclocked system
     
  9. APE

    APE Site Supporter 2015

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    There is no need to do 12mhz unless you're lazy/cheap. On most units (part of my quote you cut out to make your case) it'll result in graphical or audio corruption. There are obviously exceptions but 10mhz is more than enough to smooth out the majority of slowdowns I've seen.

    And on model 2s I'm not sure there is a convienent source for 12mhz. I just use 10mhz crystals and call it a day.
     
  10. MottZilla

    MottZilla Champion of the Forum

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    Since you have a modded system, can you tell me how well does a 10mhz overclock help the game Mega Man The Wily Wars? Particularly sad is the slowdown when you fight Cut Man for the first time. Does this overclock manage to eliminate that slowdown? Also in general, what games really benefit from an overclock anyway?
     
  11. APE

    APE Site Supporter 2015

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    I don't have an overclocked system on hand but someone just sent me a model 1 that will be getting overclocked. Luckily I also made a repro of Wily Wars (patched region free) that I'll be sure to test as soon as I have the crystal wired up.

    The only games that I've seen benefit are Sonic 2 (too many sprites on screen causes slowdown) and X-Men 2? (the snow/rain does a number on the CPU). The majority of Genesis titles I own lack any sort of slowdown making it hard to test the overclock out. While I can't think of any game that is flat out too slow to play without an overclock it is rather nice to not have it slow down at all.
     
  12. sonicdude10

    sonicdude10 So long AG and thanks for all the fish!

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    I experienced slowdown in S3&K many, many years ago (1999). I was in Lava Reef Zone act 1 playing as Sonic with Tails in tow. Had 999 rings (no cheats) and lost them all. Game completely froze for like 5 seconds on a model 2 revision 0. Scared me into thinking the game locked.

    But then any MC68000 that has to render over like 1,000 sprites would scream...

    And the console was stock with real carts. No overclocks and flash carts didn't exist in abundance yet if they even existed then.


    Would an overclock help that? I doubt it... (LOL)
     
    Last edited: Dec 28, 2012
  13. Evil Homer

    Evil Homer Member

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    That's kinda weird. I'm pretty sure no more than 20-30 rings are actually ever displayed when you get hit, regardless of what the counter says.
     
  14. sonicdude10

    sonicdude10 So long AG and thanks for all the fish!

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    Musta been a glitch then.

    Couldn't get a full count in the 5 second freeze time but there more than 20 to 30 for sure. Well north of a few hundred...
     
  15. lnx64

    lnx64 Robust Member

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    First of all I never once said KRIKzz needed to make it overclock compatible. I also never said I would bother him if it didn't work. So putting words in my mouth is highly unappreciated.

    And wow someone made the connection also evil dragon on SEGA 16. And that mattered how? I never tried to hide it or otherwise I'd use a different YouTube channel or photo bucket account.
     
  16. MottZilla

    MottZilla Champion of the Forum

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    I read a thread at another forum, domeone that has done OC mods said the EverDrive will not load games properly when overclocked. He says you need to be able to switch speeds to be able to load the game while in normal speed mode and then you can switch to your overclock speed and use the Play Game option after that.

    I have also read that the 10mhz overclock tends to have better compatibility than 12mhz. Also if Sega CD and 32X are of interest to you, people say that you need to set stock speed for those devices to work properly. You may not need a halt switch but you will need a switch to go between the stock clock and the OC clock.

    It seems the mod is quite simple, just adding a crystal and a couple switches. Mounting them nicely might be the harder part. You could probably steal the RF channel switch to use as a halt switch.

    Update: I found the answer to my question about Mega Man Wily Wars. It seems a 10mhz overclock virtually eliminates the slowdown problems, atleast judging by the first battle against Cut Man. http://www.youtube.com/watch?feature=player_embedded&v=KT3NsySaDbA

    Makes me want to install a 10mhz overclock in one of my 3 Genesis consoles.
     
    Last edited: Dec 29, 2012
  17. lnx64

    lnx64 Robust Member

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    Ok, just did a VA3 overclock. Went to 10MHz.

    Everdrive is working just fine and I do NOT have Genny 3 mode on.

    Will have proof in a second.

    No halt switch, and no stock speed setting.
     
    Last edited: Dec 29, 2012
  18. APE

    APE Site Supporter 2015

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    That has been my experience with 99% of games right there. At 12mhz a lot of titles won't boot without a halt switch but plenty boot just fine at 10mhz. If you're modding the model 3 you should install the 7 wires for 32x, GameGenie and Virtua Racing support. A bit of a challenge but well worth the time and effort.
     
  19. lnx64

    lnx64 Robust Member

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    It's a model 1 va3 not a genesis model 3.

    Actually with the ever drive 10mhz is resulting in some ok flashes and some bad flashes. Sonic 2 works fine. But batman and Robbins music is playing like a drunk.

    I have an 8mhz oscillator. Not much if an over lock but does bring the 68000 up to its rated speed as on the chip and seems to be working fine. My 9mhz osc that I got today doesn't work.
     
  20. lnx64

    lnx64 Robust Member

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    Welp, 8MHz didn't work either. I mean, the games are flashing, but somehow they are still getting corrupted.
     

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