Overclocking the DC and where to get the Increase

***quzar*** · July 14th, 2005, 20:43

Originally Posted by ptr.lynch

Seems feasible but unlikely as the whole reason, the bios will cause the DC to not boot CD-R's but it doesnt really explain why the A02 DC's cant OC.

I posted before a theory and i think that its likely, and could be proved/disproved easily if i had a rev2 mobo.

The chip that (possibly) generates the SH-4's power - IC 104. It's in a differant place on a A02 and is a differant type of V. regulator. You said before that the DC OC's well because of the high vcore of 1.99V so perhaps on rev2 boards the new IC only generates the required V. for the SH-4 to run at 200Mhz rather than the excess the rev1 and 0 produce.

Its possible but again unlikely, as why would they change it?

It is in a different place (makes sense, things have to be reorganized to add chips to the board) and is a slightly different markings, but they probably reflect a revision as opposed to it's voltage output. If anything, it provides higher voltage or more current due to the fact that the mobo itself needs more power than the external gd-rom (then again, it could be less =P)

**ptr.exe** · July 14th, 2005, 20:51

It was only a (wrong) theory

Why would it need more? that chip has nothing to do with the GD-ROM does it?

**semicolo** · July 16th, 2005, 18:58

Sorry it took so long, I lost the post (in fact I searched on dcemulation 8-).
So how do you measure Intensities ? Do you have some sort of inductancy ampmeter ? (sorry I don't know how it's called in english) But those just work for several amps, so how ?
(If you just measured between ground and the spot where you want to read intensity, I'm afraid your measures are wrong).

***quzar*** · July 16th, 2005, 20:13

Originally Posted by ptr.lynch

It was only a (wrong) theory

Why would it need more? that chip has nothing to do with the GD-ROM does it?

with the v2 the gdrom controller was biuilt into the dreamcast motherboard itself, so it is possible that there needed to be different power levels going to different things (not that the cpu would need more power, but possibly more or less current going into the VRM which would require the use of a different one possibly...)

**flaming_carrot** · July 17th, 2005, 14:48

Originally Posted by semicolo

Sorry it took so long, I lost the post (in fact I searched on dcemulation 8-).
So how do you measure Intensities ? Do you have some sort of inductancy ampmeter ? (sorry I don't know how it's called in english) But those just work for several amps, so how ?
(If you just measured between ground and the spot where you want to read intensity, I'm afraid your measures are wrong).

Yes, you measure volts in parallel and current in series. But why are you people bothering with all that stuff anyway? Seems very $#@!bersome. Instead of going to all the trouble of building your own power supply, wouldn't it be much easier to just replace the controlling resistor with a higher rated one to up the voltage? No muss, no fuss

***quzar*** · July 17th, 2005, 21:26

nobody implied replacing the powersupply... the current discussion was mostly about modifiying something near the vrm that takes power to the cpu (be it changing it for a different model, adding a pot, or adding a resistor)

**flaming_carrot** · July 17th, 2005, 22:08

Sorry but the discussion about current was all about building their own circuit to supply the CPU power, ie replacing/bypassing IC104. Which I find a little amusing since the goal seems to be raising the voltage, and that can be done by simply replacing the one resistor that controls the output of IC104. Seems a lot more efficient to me, but what do I know...

**ptr.exe** · July 18th, 2005, 13:29

you measure volts in parallel

Doh! how could i forget such a simple thing!?

To clarify, i read V. by using the ground coming from IC 104, which i assumed would be the ground fed to the SH-4 therefore the multimeter was in parallel. Perhaps im wrong?

Anyway, flaming_carrot, thats a good point but the problem is that if i was bothered to find a resistor that was in series with the output of pin 3 of IC 104 then i would have to replace it with something so close to the original value as the V. is only increasing so slightly (eg. V=IR 1.99/0.23= 8.65, so to increase that: V'= 2.01 so: 2.01/0.23= 8.74 - i know that these values for resistance arent true but for an example) i dont think i could find a resistor so close to a value as the ones used are gonna be nice round no.s such as 100 then im gonna need something like 101.7. The other way would be potential dividers but thats even messier on an already packed board.

Maybe i'm wrong and over complicating it, this is only GCSE physics, and me doing A2 i should know this stuff

**semicolo** · July 18th, 2005, 14:19

You're right for measuring the tension as ground are likely to be the same, but your intensity measure is likely to be bad if you measured in parallel like the tension, you short circuited the power supply (that's probably why you see fluctuation at first).
That's why I asked if you desolderd pins to take the measures.