Took pics and made an OC diagram

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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FamilyGuy
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Post by FamilyGuy » Fri Sep 01, 2006 3:32 pm

To overclock the DC you'll need:
- A 4pin oscilator (40 MHz works fine)
- Wires
- Soldering iron + solder
- Swith if you want to make it switchable between OC'ed and non-OC'ed
- Talent
- Steady hand
-Maybe a better fan/colling system

And a ~7.2 Oscillator if you want to sync a vmu with
the 240MHz dc

So look for it on ebay (steady hand cannot be bought)
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Post by miggi03 » Sun Sep 03, 2006 6:58 am

Hi there, I was wondering is there a any point on the board where you can get a 40mhz signal or can you only get it from an external oscilator, Basicaly can you get 240 or under using the DC alone. If not can anyone tell me the part number needed or point me in the right direction, i did try jameco but had no luck. Thanks all. :wink:
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Post by FamilyGuy » Mon Sep 04, 2006 7:51 pm

You must take a external signal .. lokk the precedent post in this thread to see diagram and aprts you need
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Post by kohan69 » Sat Mar 03, 2007 2:42 am

Wow! Great progress. Not surprised to see Morph here ;)

Can the VMU and/or the controller it's in be hotswapped without loss or corruption while game is on?

How high can the VMUs be overclocked?

Did anyone try to overclock the whole maplebus/controller port board ?
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Post by fahlim003 » Mon Apr 09, 2007 5:05 pm

My question relates to chaoticj's, and believe he bought a 2pin oscillator, like me. Looks like this
Image
Is it still possible to OC with this?
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Post by WarGames » Tue Apr 17, 2007 6:20 pm

those look like crystals, according to my electronics class, a quartz crystal has cuts in it from a laser encased in a metal "can". Using some components such as an operational amplifier (not typically used for frequencies above a few MHz, high speed CMOS IC's seem to work well for high frequencies) or transistors and capacitors to meet the Barkhausen criteria for oscillation:

B*A is slightly greater than 1
where A is the amplification gain (typically -1) and B is created from the capacitors to produce a phase change of 180 degrees (same as a gain of -1) hence -1*-1 = 1 (the product should be slightly larger than 1, which the causes the cut crystal to oscillate at it's resonant frequency. This type of oscillation is typically called "Pierce Oscillator". The quartz crystal will tend to oscillate at its resonant frequency as long as B*A is in a certain range.

since crystals can be difficult for for some, oscillators were made with the circuitry inside the metal can/casing eliminating the need for building a proper circuit to oscillate the crystal only needing to apply a voltage (usually 5V or so).

I'd recommend using regular 4 pin oscillators unless you have a decent amount of circuitry skills so you don't have to deal with those issues. (although crystals tend to be cheaper).

I purchased a bunch of 45MHz 4 pin oscillators recently which I'll be receiving soon, anybody tried overclocking with this frequency?
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Re: Took pics and made an OC diagram

Post by Morphv2 » Sat Jul 28, 2007 8:17 am

I have. But, unless you to what I did (usd direct Nexus -> PC saving), or one o' them VMU mods, save corruption thresholds become unacceptable.
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