MDD overclock

Posted by: yann86

MDD overclock - 12/18/05 09:07 AM

Ello there, this is my first post here. I've just made my first attempt of overclocking an FW800 MDD 1.25GHZ.

First thing I did was modify it to run at 1.5GHZ powered by 1.6V, it hung after only 15 minutes. Second attempt at 1.42GHZ (still 1.6V) hung after 38 minutes. Now I'm down to 1.33GHZ, 1.6V running it without problems for 1h20min. Needless to say I'm somewhat disappointed, especially after reading that the 'bulletproof' 7455 should be able to run without any problems at 1.5GHZ.

What I've noticed though, is that I've got dual 7455A's instead of the 7455B's found in all MDD overclocking guides on the net. Besides a different layout of te chip and a 3- instead of 2-phase voltage regulator, I couldn't seem to find any significant differences. Maybe I'm just unlucky or maybe it's the 7455A, what do you guys think?
Posted by: krusher117

Re:MDD overclock - 12/18/05 09:47 AM

WELCOME to MacMod! Good to see another mac user out there modding his system. Maestro (i think) has a lot of experience modding that system so he might chime in here in a little bit. Can you check the temp of your processor (not sure if MDD has those sensors) and also what kind of additional cooling have you used?
Posted by: yann86

Re:MDD overclock - 12/18/05 09:53 AM

In fact, I've built my own independantly controlled air cooling system. The CPU is being cooled by a quiet 120mm fan and a modified 80mm fan to cool the upper part of the heatsink.

Temperatures C (idle/load):
On-board CPU sensor: 44/47
Manually installed sensor: 47/49,5

Ambient temperature is about 24C. My own sensor is in between the 2 cores and is secured to the heatsink.

Thanks for the welcoming by the way laugh

Post edited by: yann86, at: 2005/12/18 17:57
Posted by: krusher117

Re:MDD overclock - 12/18/05 11:26 AM

Maybe someone can correct me if I'm wrong, but that's nothing out of the ordinary. My 1.6 G5 runs at 160 F/ 71 C OR MORE under load. Granted I don't think thats a very healthy temperature and am none too happy about it, but I can't see a G4 processor crashing due to temp at only 116 F/47 C.
Posted by: yann86

Re:MDD overclock - 12/18/05 11:31 AM

I'm pretty sure it's not the temperature as it ran 50/55 before my mod and still on 1.25GHZ. I really haven't got a clue as to what is the cause of those crashes. Probably the CPU just can't handle anything above 1.33GHZ.

Some (relatively) good news: I've been running full load for about 4 hours now, no problems sighted.
Posted by: krusher117

Re:MDD overclock - 12/18/05 11:39 AM

you're stable @ 1.33?
Posted by: yann86

Re:MDD overclock - 12/18/05 11:41 AM

It seems stable, I'm gonna let it run for 24hours straight just to make sure though.
Posted by: Waragainstsleep

Re:MDD overclock - 12/18/05 11:59 AM

Its the 7555A I bet. The A signifies it is an older chip than the ones in the guides you used which were fine to 1.5GHz. The longer a production run continues, the more the process gets refined and the higher the yield will be. Higher yield = more chips which will run at higher speeds. The fact that they changed the revision implies that they made a larger change to the process of manufacture than just the usual day-to-day tweaking.
Posted by: yann86

Re:MDD overclock - 12/18/05 12:06 PM

Waragainstsleep wrote:
Quote:
Its the 7555A I bet. The A signifies it is an older chip than the ones in the guides you used which were fine to 1.5GHz.


It's weird though as the FW800 is the most 'advanced' version of the powermac G4 (the MDD 2003 was actually the same as the 2002 version). The chip also has the 3-phase voltage regulator just like the 1.42GHZ model which is definately a 7455B.
Posted by: krusher117

Re:MDD overclock - 12/18/05 01:40 PM

I'd create a major load on the system. Play the demo of Return to Castle Wolfenstein that you can download for free.
Posted by: yann86

Re:MDD overclock - 12/18/05 02:24 PM

krusher117 wrote:
Quote:
I'd create a major load on the system. Play the demo of Return to Castle Wolfenstein that you can download for free.
Well it's been converting video files (100%load) for the last 7 hours without any problem. So I'm pretty sure it's stable at 1.33GHZ. I'll probably try to find myself a 1.42GHZ module and overlock it to 1.5GHZ though, the larger cache should also speed things up a lot.

(offtopic: what's up with the karma thingy on the left?)

Post edited by: yann86, at: 2005/12/18 22:25
Posted by: krusher117

Re:MDD overclock - 12/18/05 05:38 PM

karma is an unregulated points system. kinda like giving props to somebody when you give them some karma and scolding them when you take it away. BTW, karma to you on the successful overclocking :woohoo:
Posted by: maestro

Re:MDD overclock - 12/18/05 06:48 PM

You can easily clock it to 1.42. I did the same, but added an Apple copper heatsink. I also added 2 small fans behind it and a pci slot fan. That will keep you temps down. The case is the problem. When I put mine in a G5 case (see my mod on this site), temps went way down.
-maestro
Posted by: yann86

Re:MDD overclock - 12/19/05 07:12 AM

maestro wrote:
Quote:
You can easily clock it to 1.42. I did the same, but added an Apple copper heatsink. I also added 2 small fans behind it and a pci slot fan. That will keep you temps down. The case is the problem. When I put mine in a G5 case (see my mod on this site), temps went way down.
-maestro

Changing the case would be an option but that would include a lot of work and I'm not up for such a major mod. I don't know if you've read my previous post but I've currently got a small finned aluminium heatsink being cooled by both a 120 and an 80mm fan providing a total of about 100CFM. Also my current temperatures aren't even that high, CPU is currently 45.8C according to temperature monitor.

EDIT: I would add the copper heatsink if it wouldn't cost me an arm and a leg to get it :s I might come accross it on eBay someday, who knows...

Post edited by: yann86, at: 2005/12/19 15:16
Posted by: maestro

Re:MDD overclock - 12/19/05 08:24 AM

The heatsink is 60 bucks from Small Dog. Your temps seem great, I cant say why its locking up.
Did you replace the heatsink compound? I used Arctic silver. The stock 120mm fan actually only
cools half of the sink. You can fit two thin 80mm behind the heatink. Also, the mdds, even the newer
ones are noisey as hell, you could replace the fans with Panafloes. What was the temp when
you locked up? You could bump the voltage slightly too.
-maestro
Posted by: yann86

Re:MDD overclock - 12/19/05 08:36 AM

maestro wrote:
Quote:
The heatsink is 60 bucks from Small Dog. Your temps seem great, I cant say why its locking up.
Did you replace the heatsink compound? I used Arctic silver. The stock 120mm fan actually only
cools half of the sink. You can fit two thin 80mm behind the heatink. Also, the mdds, even the newer
ones are noisey as hell, you could replace the fans with Panafloes. What was the temp when
you locked up? You could bump the voltage slightly too.
-maestro

I live in Belgium so including shipping costs that would make quite an amount of money.
I replaced the heatsink compound (arctic silver 5) with every test. Also every fan in my system has been replaced by quieter models. As I've said before, I've placed an 80mm fan behind the heatsink where it normally wouldn't be cooled, this seems a bit more effective than 2 80mm fans also because it's been proven that blowing air across a heatsink results in cooler temps than sucking air over it.
Posted by: maestro

Re:MDD overclock - 12/19/05 10:11 AM

Its seems that you have done everything right. Didnt you see which chips you had when you cleaned
the paste off? Mine was a 2003 model with 1.25 A 4mb cache. The 1.42 and 1.25 are actually the same
chip designation but with a higher clock listed on it. Not all chips clock the same. It looks like you
should stay at 1.33.
-maestro

Post edited by: maestro, at: 2005/12/19 18:16
Posted by: yann86

Re:MDD overclock - 12/19/05 10:17 AM

Just my luck :angry:
By the way about the voltage (overlooked it in your last post): I also bumped it up to 1.6V, when I noticed it wasn't stable I went up to 1.625V without improvement. Currently 1.33GHZ @ 1.6V, guess this is the end of my (quite unsuccesful) overclocking attempt frown

Post edited by: yann86, at: 2005/12/19 18:17
Posted by: Waragainstsleep

Re:MDD overclock - 12/19/05 11:01 AM

I'd quite like to overclock my single 1GHz MDD, but I was thinking of clocking the bus up rather than just the CPU. If I can get the bus up to 1.67MHz, It will boost the CPU up to 1.25 anyway, and take faster RAM too. All together should make a fairly hefty difference.

Does anyone know how to OC the bus?
Posted by: yann86

Re:MDD overclock - 12/19/05 11:44 AM

Waragainstsleep wrote:
Quote:
Does anyone know how to OC the bus?


There's a guide on macbidouille (don't worry, it's english) on how to overclock a dual 867mhz MDD's bus speed. I guess it's all the same.

EDIT: forgot the link http://www.macbidouille.com/article.php?id=89&page=3 :silly:

Post edited by: yann86, at: 2005/12/19 19:50
Posted by: maestro

Re:MDD overclock - 12/19/05 12:31 PM

Some people have had success oc'ing system busses. Im absolutely against it. They are not as stable, and if
it all goes south, so does you mb, and cpu and well, what ever it wants to take with it. I myself got in a little
too deep on the MacMod Server Mod, and toasted the board and cpu. Everything else seemed okay. We learn
from mistakes but your's could be an expensive one and I already had replacement parts waiting. You may want to
look at some cpu upgrades (which use newer cpus, but are still with the fat cache) or go all out and buy a G5.

By the way, I was all for taking mine to 1.5dp, but could not afford the risk and just bought a dpG5 instead. Man was
it worth it.
-maestro
Posted by: Waragainstsleep

Re:MDD overclock - 12/19/05 01:10 PM

I will admit some trepidation at the thought of overclocking my MDD's bus. However, looking at the specs across the board of MDDs, mine is a second generation with FW800. All the first gen were running a 133MHz bus like mine, all the others run 1.67MHz. It looks to me like my machine is the first example of Apple's tendency to deliberately cripple the base model in every given range of PowerMacs (Think about the G5s with only four RAM slots). So based on this I figure there is a good chance that my board is the same as the other rev2 MDDs, and quite likely, the chip is the same too. Just downclocked by Apple, since they couldn't get the top of the range ones to run any quicker.....

I guess I could check the part numbers on some logic boards.

Any thoughts?
Posted by: maestro

Re:MDD overclock - 12/19/05 03:32 PM

That may very well be. Check you bus controller, the Motorola chip and see what it says. By all means, try it, but be careful and take the time to be causcious. Good luck.
-maestro
Posted by: nighthawkfx

Re: MDD overclock - 03/07/13 05:58 PM

I too have 1.25 MDD that I tried to OC, to 1.5ghz, it did work for about 15 min, then I got the 'warning' that I need to restart my computer.. I would to take the speed down in increments but charts I found are not real clear as they dont show the bit order to resistor placement tho pix do show pll cfg#s. (I got where I did because 1.5g - 10111 didnt leave much room for error) bitsandpieces archive. Id like to try 1.417ghz

Any help on bit order be good, I do understand binary-the chart isnt clear which way MSB-LSB reads, I dont have enuf examples.
MDD in a MacII case, watercooled, temp on cpu block: 92F
Posted by: NucleusG4

Re: MDD overclock - 03/07/13 08:04 PM

You do realize that you're responding to an 8 year old thread? Those guys have prolly gone to the great CPU in the sky by now......
Posted by: nighthawkfx

Re: MDD overclock - 03/07/13 09:25 PM

yes I do ... first clue was the bitsandpieces is archive only,
just trying to find some info
Posted by: NucleusG4

Re: MDD overclock - 03/08/13 03:57 AM

Roger that.