[Jacques]

I was going to do a long writeup of my O2 upgrade, but I've finished getting my O2 to good install state and wil be focussing my efforts on my Octane from now on. But I don't want to leave the upgrade process undocumented on this forum so here is the short-short version.

The process was previously covered by ChicagoJoe on Nekochan, I've had to cobble together various sources of information to get to this point, so here it is. 

Shopping List :

An O2 suitable to accept a R10K / R12K (See my previous guide)
R10K 250Mhz O2 cpu module (you can also use a 225Mhz R10K CPU as well, I'll try and find the resistor settings for this)
R12K 300Mhz CPU, mine came from a donor Octane Pimm.
A fine tipped soldering iron, solder (I used 60% lead), tweezers and a steady hand.
5mm Hex key / Allen Key.

The usual disclaimers follow : You do this at your own risk. You need a very steady hand to solder the resistors in place,  make sure you follow the usual anti-static precautions, the CPU modules are very susceptible to static discharge.

I started off by removing the R12K CPU from the Octane PIMM.

1) Remove the four no. sprung hex screws from the top of the Octane PIMM, together with the two smaller screws on the voltage regulation board.



2) The bottom section of the heatsink will be free for removal. Put both of these to one side. 


Bottom of Octane PIMM

3) Gently remove the CPU from the socket and place it to one side, that's if it's not stuck to the heatsink. If the thermal tape tears you will need to replace it with similar thickness tape, you can buy these from most online electronic retailers or Amazon etc. Mine came off in one piece.



Top of Octane PIMM


CPU stuck to heatsink


Next Up - The O2 PIMM

1) Disconnect the fan from the PCB

2) Undo the four no. hex key screws, once removed you can safely remove the rear retaining bracket. Careful to keep the plastic 'gasket' on the bracket. 







3) Remove the CPU and place to one side, do not touch the golden contacts in the socket.  We'll be working on the pcb next. Look at the rear of the O2 PIMM, go and find the resistor bank that looks like the bottom right in the photo below.




We will working in the bank of resistors 507 - 559 for this mod. Small aren't they!

In this mod, we are keeping the SysClk frequency at 100Mhz, so no need to change the SysClk resistor. If you were running a 225Mhz R10k, your SyClk would be running at 90Mhz. We also have to aware of another factor here, and that is the clock multiplier value.  A 250Mhz CPU clock would be 2.5 x 100Mhz (CM * SysClk), a 300Mhz CPU clock would be 3 x 100Mhz (CM * SysClk), etc.



In order to change our multiplier from 2.5 to 3 (to go from 250Mhz to 300Mhz) we need to change resistor 537 to 538 (move it across) and 552 to 553. 

How small are these? Well, very small! I managed to ping one away with a pair of tweezers and miraculously found it 2 days later on the carpet! 




I found the best way to work these is to desolder the resistor, clean the pads with some solder wick, then prep the new pads with a shaving of solder. The shavings are about 1mm in size, if you try prep straight from the wire you're in for a tough time. Place the solder shaving on the pad, apply heat and it should melt right on. 

Keep the resistor in place with some sharp tweezers while you solder, the best way is to position the resistor on top of the solder 'lump', while keeping the tweezers on top of the resistor apply the sharp end of the iron tip to the side and press down gently on the resistor, the resistor will sink in toward the pad. 



Some solder shavings. 

Once you've moved your resistors you should have a resistor layout as below.




Changing the SysClk.

I've not done this, but there are reports the resistor layouts for the System Clock value changed between pcb updates, the best I can find is the following : To go from 90 to 100 you need to swap resistors R644 to R646 and R649 to R650 on some boards, but on my board the resistors correspond to R647 to R649 and R654 to R655.  I can't guarantee this though! Best I can find to describe it visually is as below.



Closing thoughts

As always, don't over tighten things when re-assembling, and re-assembly is the reverse of taking apart. 

Ive not changed the fan on my module, it's been running fine for about 4 weeks now, no issues what-so-ever. It doesn't feel a huge amount faster than the R10K 250 for average use, but I suppose every second counts if you're compiling an app or doing a quick render. It does feel snappier though. It is a lot faster than my RM5200 300Mhz cpu!

Hopefully the above is some help to those contemplating the upgrade.

[gijoe77]

how do you go about figuring out which resistors to move? I've got a 400mhz o2 PIMM that I would love to try to overclock to ~450mhz but I have no idea how to figure where to begin...

[Jacques]

No idea, ChicagoJoe figured it out. I just scrambled together bits of info from Ian, some French website and old Nekochan archive posts.

If old neko posts are anything to go by, the 400 doesn't overclock very well from memory, I think the most somebody got was 425 Mhz odd, not worth risking a PIMM. Even at that speed it threw up errors, most likely due to cache issues.

[BrainStorm]

Excellent writeup, JacquesT!

Both of my O2s are R10k@175MHz, and I've never got into an O2 at this level, so I'm wondering what could be done with the sorriest of the non-R5k modules. Even with 15k RPM HDs, they are less fun than a dumb terminal connected to a rock. I have an abundance of 195MHz R10k Octane PIMMs and some others for donor parts, but no clue of the 175 board's capabilities. I really need another project to take up counter space I don't have.

We need to add a wiki topic for hardware overclocking and start a repository of information and tuts on the subject. I would especially appreciate just tech docs listing resistor and jumper configs for [n]CPU on [n]PIMM at [n]clock, maybe with photos of the different module boards in their factory configs. I'll try to dig up the stuff I had archived and submit it somewhere. Who else has photos/info?

[Jacques]

Excellent writeup, JacquesT!

Both of my O2s are R10k@175MHz...

...are overclocking and start a repository of information and tuts on the subject. I would especially appreciate just tech docs listing resistor and jumper configs for [n]CPU on [n]PIMM at [n]clock, maybe with photos of the different module boards in their factory configs. I'll try to dig up the stuff I had archived and submit it somewhere. Who else has photos/info?

Agreed! Especially the various PIMM and resistor layouts.

With the 150/175Mhz versions, these may have a different ASIC which could cause some latency issues. Not sure if you can therefor do a straight swap.

Top of the 250Mhz R10K PIMM below.