Overclocking the DC and where to get the Increase

**Cross** · June 28th, 2005, 16:40

Originally Posted by ptr.lynch

Dozens of Dreamcast fans have spent hours trawling over DC mobo's trying to figure out the point where the voltage supply to the Sh-4 is produced and no one as of yet has found anything... but your gonna ask your mates, so we can all sleep easy at night now

Just joking, but this info won't be found easily on the internet as no one knows of anyone who has done it yet.

LOL they r not internet searchers, they love to trace circuits. They are some of my military buddys and thats what they do for the military. I don't expect them to do any better but we all have people who if we think someone could do it we would say them. I trust them just because I know if its beyond me they always seem to love jumping in and doing it.

**obelisk** · June 28th, 2005, 21:31

bump for dc. keep up the stuff, and let us know your findings.

**Morph** · June 29th, 2005, 05:04

I have faith in you man. Hell, if I had a logic analyzer, I'd do it myself. But, eh, not so lucky.

**Cross** · June 29th, 2005, 07:32

We shall see I am taking them my spare DC tomorrow. I am not sure how long it will take but here goes nothing lol.

**Morph** · June 29th, 2005, 12:34

good luck! keep us posted.

**ptr.exe** · June 29th, 2005, 13:29

Cross i apologize, but when someone on a forum says "My mate..." you immediately just assume its nonsense. Hopefully they can find something.

**Morph** · June 30th, 2005, 22:31

Well, I just got a reply from someone at that site who definately seems to know his stuff. Get this, that CPU line? Thats NOT a CPU line. The the motherboard FSB line. So when we overclock the CPU, we are actually overclocking the RAM and everything else. Here is the reply.

"This is not entirely correct. The basic clock signal comes from a 13.5MHz
oscillator that is fed to a PLL that indeed generates a 54MHz and a
33.33MHz signal. The 33.33MHz signal is fed to the SH4 which generates a
200MHz signal that is used internally, but it also generates a 100MHz
clock that is fed to the rest of the system, including the Holly chip
(which includes the graphics core but also lots of bus control logic) and
SDRAM. That 54MHz from the PLL is indeed also fed to Holly, perhaps it is
even used internally by the graphics system, I'm not sure; the main stuff
would be running off the 100MHz clock though. The primary use of this
clock seems to be to as a pixel clock for the video encoder.

You state that you want to overclock the SH4 to 300MHz, by I'm guessing,
feeding it a 50MHz clock instead of 33MHz. You think the problem is the
1.8V. Sorry, I can't help with that at the moment, but I'm thinking there
are lots of other problems too, such as clocking the GPU and main/video
RAM at 150MHz instead of 100MHz..."

If I understand his point correctly, I will probably also have to boost the FSB (ex-CPU) line to keep it synced with the CPU. Which isn't a problem, it simply changes the playing field a bit.

**Cross** · July 1st, 2005, 06:14

SO we are also OCing the RAM and other parts...hmm I will pass this on.

**Morph** · July 1st, 2005, 06:40

nonono, ignore that whole bit of information. The CPU speed is still independant of the FSB line. So all I need still is the 1.8v thing. Thats just clarifying that what was previosly considered a CPU-only overclock is in fact a FSB overclock.