[Waragainstsleep]

Anyone ever OC the bus on a MDD G4? Particularly the single 1GHz (FW800) model?
I figure clocking the bus from 133 to 167 will not only boost data throughput, and add 250MHz to the CPU clock, but it should allow me to run PC2700 RAM (at full speed) instead of the PC2100 stuff. Altogether, I reckon that would be quite the speed boost. The question is, will it survive?

I'm guessing (because all other MDDs except the single 867 had a 167MHz bus), that it should be happy enough to run a little faster.

[Grrr]

In my limited experience of overclocking CPU's and Bus's, its hard to do any real lasting damage. It either works, doesnt work, or works and is unstable. In the case of the last 2, you just have to undo some of your work and be a little less enthusiastic, and try to go for a slightly lower speed gain.
Can be tedious, but worth while.

[Waragainstsleep]

I haven't even bothered looking up the settings yet, I assumed going from 133 to 167 would be the smallest possible increment. I figure the board will be OK at that speed (I'm guessing they downclocked it from 167MHz. Apple have been in the habit of deliberately crippling their slowest PowerMacs (in any given range) these days.

Am I right in thinking that the bus OC will automatically result in the RAM running faster?

[Concorde Rules]

Yes it will, well should do anyway.

I have a Dual 867 MDD, if this works (and is easyish to do) I may need to buy some PC2700

Concorde

[lenox]

The ram won't run faster unless you buy ram that supports the higher speed, but yes - then it will. I have a dual 867mhz mdd and I may eventually do the same thing...now that Apple has made it clear (to me, at least) that buying a PPC cpu upgrade isn't the most forward-thinking idea.

[piet]

I have the resistor on the motherboard (r676) removed to make the bus run on 167 hrz but were are the cpu board settings??
The info for a dubbel cpu is not helpfull (very different)
There are 2rows of PLL resistors markt HI and LO ?? an then there is the cpu multiplier.
For the cpu to work on a hi speed it must have more volt so where are the settings for that?
The generated heat is in my g4 taken care off by watercooling and it is very silend to!
I put in 3200 DDR ram what reads as 2700!

[Waragainstsleep]

The CPU setting is a multiplier. If you up the system bus without changing the CPU (multiplier) settings, the CPU speed should have gone up too.

[piet]

multiplier yes but where on the cpu board and what settings?
Or is there a web-side where the cpu board is explaint?

[Waragainstsleep]

http://www.themacaddress.com/pnews.php?page=ppc74xx

[treebark7182]

after browsing the net all i could come up with is that its a simple 1 resistor removal but i cant find a guide or anything. I'd love to up the bus on my dual 1ghz 133bus to 167 and getting a free upgrade to dual 1.25ghz. The resistors for the cpu itself are the same for the 1ghz at 133bus and 1.25 at 167 bus. If anyone has a guide or can post one that would be fantastic.

[piet]

For the DP go to www.macbidouille.comand www.xlr8yourmac.com

[Waragainstsleep]

I think its the single proc we're looking for here. The DP ain't gard to find.

If you look at the table I posted above from themacaddress.com, you'll see the left hand column gives the PLL settings you need for a given multplier setting. These jumpers are labelled the same way as the ones on the DP module, so the settings are ultimately the same for the single, its just that the resistors may not be in the exact same place.

But like I already said, if you've found the resistors to OC the bus, then thats going to get you a boost in clock speed too, unless you downclock the multiplier. You said your RAM now registered as PC2700, but did the CPU speed not go up too?

[piet]

i have not found the resistors on the cpu board for bus/cpu/volt settings so no speed increase yet.
i probably have to fit a switch block and try endlessly