Finally

Pyrosurfer · Post by **Pyrosurfer** » Mon Dec 20, 2004 6:25 am

I'm sure the dc has some sort of onboard voltage regulator to bring 3.3V down to whatever the processor uses. If the dc's pll is not adjustable though, I don't think this will be either.

Matt · Post by **Matt** » Mon Dec 20, 2004 6:43 am

It definately does, can't you still put a different crystal on it to generate a different multiplier. And if you could find it (im sure theres SH4 pinouts on the net), cut the voltage trace, insert a wire and up the voltage with some sort of external power

Pyrosurfer · Post by **Pyrosurfer** » Mon Dec 20, 2004 6:46 am

I think Kamjin said before it is a bad idea to replace the plls crystal.

Epicenter · Post by **Epicenter** » Sun Jan 02, 2005 12:53 am

It definately does, can't you still put a different crystal on it to generate a different multiplier. And if you could find it (im sure theres SH4 pinouts on the net), cut the voltage trace, insert a wire and up the voltage with some sort of external power

First off, the pin is a BGA-similar design embedded in a multilayer PCB. Good luck finding the trace to cut! Also there will probably be MULTIPLE vcc (core voltage) pins, not just one. That won't be easy. At any rate, you don't use an oscillator to select a multiplier. The multiplier appears to be internally locked into the SH-4.

The formula for CPU Clock is: Bus Speed x Multiplier = Final CPU Clock. Here, it would appear to be 33 x 6x Multiplier = 198 MHz CPU Clock.

Replacement of the PLL itself is also going to be a bit of a nightmare, you'd have to match up the multiplier/divisor values for EVERY Clock, not just the CPU. Video, et cetera. Also, this will have NO effect on the core voltage (VCC) to the SH-4.

The most likely path to getting a Dreamcast's SH-4 to 300 MHz? Supercool it with a high-wattage thermoelectric cooler (though, fitting a heatsink able to cool the TEC under that RF shield and drive assembly will be tricky, you'll have to make a ribbon cable or similar to get the drive away from it) .. then replace the RAM with something rated for higher. Also, different CPUs will take more abuse than others, so you might just buy a few Dreamcasts and try it on each one.

I'd also strongly recommend a variable oscillator so you can tie this onto the clock output trace to the SH-4 and gradually step it up AFTER boot rather than try to boot at extreme frequencies where it's very likely the BIOS will crash and bring down the boot process.

Zealous zerotype · Post by **Zealous zerotype** » Sun Jan 02, 2005 2:01 am

Yea just simply replace the ram in the dreamcast no problem.....

Epicenter · Post by **Epicenter** » Sun Jan 02, 2005 2:29 am

I would have to assume that's sarcasm.

If you're adept at soldering it's not a difficult task. The RAM's not anything propreitary, you can buy it at a number of places at a higher rating, then install that in the place of the old RAM.

Not that trying to feed on a new VCC will be any easier, wise guy.

Zealous zerotype · Post by **Zealous zerotype** » Sun Jan 02, 2005 2:40 am

Jesus christ please stop.
NOW.
Oh I can tell you have an insane I.Q. by how you picked up my sarcasim.
To you I tip my hat.

Epicenter · Post by **Epicenter** » Sun Jan 02, 2005 12:12 pm

Apparently posting the truth in a thread full of misinformed statements that will lead to dead Dreamcasts is a crime around these parts? Well damn, guilty as charged.

bizzle · Post by **bizzle** » Sun Jan 02, 2005 12:17 pm

zerotype, don't give Epicenter a hard time. He is a good man who deserves much respect.

Epicenter · Post by **Epicenter** » Sun Jan 02, 2005 12:27 pm

Hey, thanks.

Alexvrb · Post by **Alexvrb** » Mon Jan 03, 2005 10:55 pm

Epicenter wrote:That won't be easy. At any rate, you don't use an oscillator to select a multiplier. The multiplier appears to be internally locked into the SH-4.

That's what I wanted to know many posts ago. I was tired of being told to replace the crystal, since that doesn't have jack to do with the multiplier. It was more out of curiousity anyway.

Epicenter · Post by **Epicenter** » Wed Jan 05, 2005 3:38 am

Raising the multiplier would be ideal as the RAM clock wouldn't rise. But unfortunately, it seems to have been masked into the chip with everything else, and after analysis of the chip that belief's only been reinforced. I don't see any means to externally set this value. Sorry.

Prophet][ · Post by **Prophet][** » Wed Jan 05, 2005 4:34 am

Just to let anyone that doesn't know the website has changed and is now at http://www.ucm.cjb.net

Zealous zerotype · Post by **Zealous zerotype** » Wed Jan 05, 2005 7:12 am

Just so everyoen knows the guy who wrote that english guide. He has tried 280mhz on a (1) model. It did nto "boot" just got a white screen. Also flipping the switch afterwards does not work as it locks up the dc. Becuase it is not getting anythig for a short second. So he is gona try a (0) sometime soon to see if it will go to 280.

kohan69 · Post by **kohan69** » Mon Apr 17, 2006 11:34 pm

http://nifty.amikai.com/amiweb/browser. ... c_id=nifty

jap guide in 1/2 english > english guide