Official DC Overclocking thread

Discuss modifications you have done or plan to do to your Dreamcast or any other hardware, or discuss devices you want to build. If your console does not work or is acting up, ask about fixing it in here.
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Official DC Overclocking thread

Post by robivy64 » Wed Nov 15, 2006 10:09 am

Hello!

I'm sure most of you have seen the overclocking tutorial I wrote a few years ago featured on Devcast. I get all kinds of questions about the procedure, results, etc...

My time has become increasingly limited, so I wanted to post this thread to allow people to ask me questions relating to this particular mod. Thanks!

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Post by FamilyGuy » Wed Nov 15, 2006 6:10 pm

I overclocked mine and it works fine at 240MHZ but what is the max power anybody had hit ??
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Post by Morphv2 » Wed Nov 15, 2006 6:28 pm

I believe matthemodder hit 286. You'd have to do some looking, or asking.

I have hit very high clockspeeds, but stability takes a nosedive after 276Mhz. From our assumptions at dcdev, 2 things could be holding it back from clocking higher:

1. CPU voltage
2. Slow memory

It is possible that the vcore line was located, but the memory is another story.

On most models, the system memory is rated for 10ns, which means it was rated for 100Mhz only. A lot of the time, the GPU and Sound memory is rated for 8ns aka 125Mhz, which means you aren't technically "overclocking" that memory until you peak over 125Mhz. However, the fact that your system memory is only rated for 100Mhz operation, means that ANY increase in speed is pushing it over designed specifications.

I have a board with 9ns memory for everything, but lord knows if the oddball even works.
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Post by neoknux_009 » Sun Nov 19, 2006 4:29 am

so has anyone gotten any good results? the video given couldnt really tell me anything. results as in... a game that had some lag time has improved? aka shenmue people loading or soa b4 battle scene?

otherwise theres not much point in me overclocking. i dont really use my dc for wathcing movies.
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Post by Prophet][ » Sun Nov 19, 2006 7:00 am

do a search on this forum, you will find their is another official over clocking thread which has much discussion and information on this.

Also, I am the moderator of Devcast if you need anything changed or updated.
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Post by FamilyGuy » Sun Nov 19, 2006 11:39 am

I've got about 10% speed increase in dreamsnes with my oc'ed dc at 240 MHZ
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Post by Morphv2 » Sun Nov 19, 2006 6:41 pm

If someone can prodive me with a game/demo/THING with an FPS counter, I'll whip together a video. I can compare 200, 240, and 270. Preferrably something that lags like crap.

I need to put my Radeon 8500 AIW to SOME kind of use....
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Post by neoknux_009 » Mon Nov 20, 2006 5:44 am

well, lets say i do overclock my dc, where would you get the oscillator?

is this correct?

http://www.cascadesurplus.com/catalog/p ... cts_id=631

or would an electric store have one?
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Post by Prophet][ » Mon Nov 20, 2006 9:07 am

you could get a 555 timer and make your own, the beauty of that would be that it is variable, but it is hard to get precise (ie, down to an exact frequency)
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Post by robivy64 » Tue Nov 21, 2006 9:30 am

Digikey.com sells them, but if you want to go absolutely cheap, you can salvage them from old circuit boards.

If overclocking is something you might do to other systems, you can get some good bulk-buys on ebay. Only the 4-pin variety will work.

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(Note: the other 2 pins aren't visible in this pic)
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Post by Morphv2 » Fri Nov 24, 2006 4:27 pm

I generally just use Ebay myself. WE're talking you can get these things in BULK for like $10-$20.

Also, prophet, I kinda jimmied myself a "switch" together. It's not completely variable, but you get the idea. It contains 3 oscillators (37Mhz, 40Mhz, 45Mhz) inside a cheapo Radio Shack housing, all soldered to a small PCB with 4 switches (one for each clockspeed, Normal, 112Mhz, 120Mhz, and 135Mhz). It's bolted to the side of the DC itself, with a small hole drilled into the side of the DC, and the side of the housing to run the necessarry wires through.

It's crude, but it works like a dandy.
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Post by FamilyGuy » Wed Nov 29, 2006 10:22 pm

4 switches (one for each clockspeed, Normal, 112Mhz, 120Mhz, and 135Mhz)
I bet you mean Normal, 222, 240, and 270,

Because the DC multiplier is 6, so 6*37, 6*40, and 6*45.

Does the 45mhz works well ??
I tried it at 48Mhz but I got a black screen.
40Mhz works perfectly thought.
I'm working on a synch'd VMU
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Post by Morphv2 » Thu Nov 30, 2006 9:46 pm

I rate by front side bus speed, not the entire clockspeed. When I overclock the DC, like a computer, I am overclocking the whole bus, not just the CPU. Also, its a multiplier of 2. The clock signal is multiplied by 3 from the PLL (for the FSB), then further by 2 for the CPU.

You'll have to show me how to sync a VMU, I use a Nexus part I got from Newegg (r.i.p.) with a USB cable. I usually save directly to a computer with it. It'd be much better to use a solution like yours.

Once I cut the procrastination, I'll do a video. For me, 270Mhz works fine, although I get occaisional corruption. In dcemu, we have a far more detailed thread on the subject.
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Post by neoknux_009 » Sun Dec 03, 2006 7:19 am

when you guys say sync vmu, i assume it means that the dc can still read information from the vmu, but it cant show pictures or give sounds with the games. right?

if 270mhz works, then excellent. thats my next project...just waiting for the video.
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Post by robivy64 » Mon Dec 04, 2006 1:40 pm

Morphv2, what revision of dreamcast do you have? I assume it isn't a version 2 if you are hitting 270 MHz.
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Post by muthafied » Tue Dec 05, 2006 6:22 pm

Hi there don't know much about overclocking a dc, so how do you know if you have successfully overclocked a dc apart from the game speed and is it true that you can't use your vmu once your dc has been overclocked? Thanks.
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Post by miggi03 » Thu Dec 07, 2006 10:06 am

Hi there, some of the links to the oscillator needed are outdated. Anyone know where i can pick one up? I live in the Uk been googling all afternoon to but no luck and ebay ain't got any. Thanks.
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Post by robivy64 » Fri Dec 08, 2006 11:03 am

muthafied wrote:Hi there don't know much about overclocking a dc, so how do you know if you have successfully overclocked a dc apart from the game speed and is it true that you can't use your vmu once your dc has been overclocked? Thanks.
Well whenever I overclock a Dreamcast I always turn it on once I disconnect the stock clock signal to ensure it will *not* boot. So when I hook up my new speed and it boots, I know it's running on the faster speed. If you have a game that is nutorious for slowdown like Shenmue, Psyvariar 2, or Sega bass Fishing, you can generally see an increase in performance.

As for the VMU issue, i've never tested this, does it not function?
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Post by robivy64 » Fri Dec 08, 2006 11:05 am

miggi03 wrote:Hi there, some of the links to the oscillator needed are outdated. Anyone know where i can pick one up? I live in the Uk been googling all afternoon to but no luck and ebay ain't got any. Thanks.
http://cgi.ebay.co.uk/SMT-SMD-40MHz-CRY ... dZViewItem

40 MHz part, this would make your Dreamcast run at 240 MHz. Auction ends in ~4 days.
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Post by miggi03 » Fri Dec 08, 2006 7:51 pm

Thanks bought it just now. :P

[img=http://img246.imageshack.us/img246/6788 ... ut5.th.jpg]

EDIT, still waiting on the crystal, *sigh* as soon as the mods done ill post the results.
Last edited by miggi03 on Thu Dec 14, 2006 5:55 am, edited 1 time in total.
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