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G5 1.8 processor on 1.6 mainboard?

If you don't want to contact Isobe, here's BadAndy's guess.

There is another small service Processor in our G5 Tower and it's hooked to I2C...

You may have to flash the ROM on the service processor, if there isn't a jumper on the motherboard.

Edit: POR is also on IBM's site ...

mvd_1.gif


The power-on reset (POR) logic of the IBM PowerPC® 970FX processor is more sophisticated compared to previous PowerPC processors that rely on jumpers to select operation modes. The PowerPC 970FX processor initialization is controlled by a pervasive logic that requires communication with an external service processor through an I2C bus.
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v-i-c- said:
that's the point here - if we get rid of the problems the answer is: yes

1. i buy a 1.6 processor and sell the 1.8 on ebay (will work for sure)

2. i buy a 1.8 single (2003) mainboard and sell the 1.6 single board on ebay (will work for sure)

I NEED HELP! 1&2 is the last solution that i can afford because it costs $$$ again and this G5 was only a few $100 cheaper than a new 1.8 single and i still want to see it below that price.

this is the result compared to the same machine at high settings (and the frankenstein G5 still stuck at it's low settings):

http://ladd.dyndns.org/xbench/merge.xhtml?doc1=96222&doc2=96376
Click to expand...

Thanks for the explanation

I saw on the pictures that the new/2nd cpu is just hoocked up to the mother-board with 4 scrwes. but is it connected to the MB trough those or did I miss some wire :confused:
 
v-i-c- said:
1. i buy a 1.6 processor and sell the 1.8 on ebay (will work for sure)

2. i buy a 1.8 single (2003) mainboard and sell the 1.6 single board on ebay (will work for sure)

3. some king of soldering helps us and solder the jumpers on the processor board (like shown on that website - link above) that the processor runs with 1.6 mhz and 800mhz bus.

4. some king of soldering helps us and solder the jumpers on the processor (how????) that the processor speed is still 1.8ghz but bus speed is set to a lower setting than the max mainboard bus speed is (maybe 600mhz like the "new" G5 single 1.8)

5. someone finds out how to overclock the mainboard speed to 900mhz (soldering or not soldering)

6. the way i would prefer (but no big hope): i find a way to patch the firmware of the G5 that this "safety mode" will not be activated and/or i find an app that gives me control over fans and processor speed (which is possible but i think not existent yet)
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I have never done anything like this, but here is what I think:

6. doesn't work. There is no way an 1.8Ghz CPU will work with a 800mhz bus.
3. seems the easiest solution. When the processor presents itself as an 1.6 Ghz processor the logic board will probably just accept it.
4. Is the coolest solution, but probably the most difficult since you need to change the bus speed, the processor multipliers, ram multipiers (if they have those) and maybe even the flashrom. If you got it working though, there is even the foresight of running at speeds above 1.8 Ghz, which would be ultra-cool.
 
saw on the pictures that the new/2nd cpu is just hoocked up to the mother-board with 4 scrwes. but is it connected to the MB trough those or did I miss some wire
Click to expand...

i wish i had an 1.6 processor :( - but i only got an 1.8 so it's not a "new/2nd" processor...

right the processor is fixed on the mainboard using 4 special screws.
it's connected to the mainboard with a kind of multipin slot under the processor board - no wires



@Sun Baked:

any further idea if there is really the possibility to flash that service processor?

do you have the email of Isobe?
 
v-i-c- said:
@Sun Baked:

any further idea if there is really the possibility to flash that service processor?

do you have the email of Isobe?
Click to expand...
Don't know if it's a flash for each bus speed, or a resistor setting (telling the service processor which settings table to use).

You sort of need to compare a 1.6MHz and 1.8MHz board -- and Apple did reship some 1.8MHz machines as 1.6MHz machines when the killed the SP 1.8 the first time.

They also disabled PCI-X on them, so it must be possible to either flash them or move jumpers.

---

He's a member on ARStechnica (M.Isobe), and widely found by doing a google search using "Michiro Isobe AND overclocking"

There is also a thread on ARS you might want to drag back up to the top...

Over-Clocking the PowerMac G5 Thread
 
No answer from M. Isobe yet...

anyone else with new ideas or infos?
 
v-i-c- said:
No answer from M. Isobe yet...

anyone else with new ideas or infos?
Click to expand...
Join ARS and drag the thread back to the top, ARS is generally more technical than here.
 
v-i-c- said:
i wish i had an 1.6 processor :( - but i only got an 1.8 so it's not a "new/2nd" processor...

right the processor is fixed on the mainboard using 4 special screws.
it's connected to the mainboard with a kind of multipin slot under the processor board - no wires



@Sun Baked:

any further idea if there is really the possibility to flash that service processor?

do you have the email of Isobe?
Click to expand...

Thanks for that

Hope your project turn out well, becasue then we might see more people building costom G5's :D
 
i'll try to install yellow dog linux on the g5 today - just to see if the linux fan driver will slow down the fans.
 
yes fans run fine under linux - no vacuum cleaner sound anymore - yellow dog linux shows 1800MHz as processor speed but since osx said the same i don't trust that. i need to find some benchmarks and comparison charts of other G5 1.8 or 1.6 to see how fast it really is - any idea?

it really looks like i need a new kernel extension for thermal management now. but that's not existent.

btw: there was an major update to the selfmade G5 1.8 on a 1.6 Logicboard site
 
v-i-c- said:
yes fans run fine under linux - no vacuum cleaner sound anymore - yellow dog linux shows 1800MHz as processor speed but since osx said the same i don't trust that. i need to find some benchmarks and comparison charts of other G5 1.8 or 1.6 to see how fast it really is - any idea?

it really looks like i need a new kernel extension for thermal management now. but that's not existent.

btw: there was an major update to the selfmade G5 1.8 on a 1.6 Logicboard site
Click to expand...

I like what you have done to your web page ;)
Hope that you will be able to get the fans normal in OS X.
By the way how does Linux work on mac :confused:
 
By the way how does Linux work on mac
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i used Yellow Dog Linux for PPC they have a version with thermal drivers for the G5. i don't really know if it's really running at 1.8GHz now - i found a benchmark but it crashed while running lol - there is a kind of system overview which shows bogomips and i compared this value with some that i found with google, but i didn't found bogomips of a G5 1.8 running YDL, so i calculated it and it looks like it's a faster than 1.31GHz but slower than 1.8GHz. so maybe YDL is faster today (i use 4.0) or faster than other linux for PPC because i think those values i found was from other linux versions. maybe someone can help out with his YDL 4.0 G5 1.8GHz values? anyway it works fine and it's really quiet. but it's no solution for me because we want to use the mac as a mac.
 
Hector said:
he's saying the only mac quieter than the G5 is the cube.

no computer on the planet is quieter than a g4 cube with a flash based HD (you can get them they are very expensive).
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That and the iMac DV 400mhz. Convection cooled as well.
 
Remember there will also be a bank of jumpers for the HT PCI-X controller (which could/should enable PCI-X on the 1.6 board)

Edit: Remember I asked for some pics of this controller (or the part number and manufacturer) if you can find it, which should be where the majority of the PCI trace go.

BadAndy hoped there was a hash table controlled by jumpers... hopefully this does turn out to be the case.
 
Thermal Problems

Hi Chaps,

I'm really sorry to ask a favour on my first post here, I know it's not the done think on forums, but I desperately need the Apple Calibration Software to stop the McDonnell-Douglas Boeing type fans on my G5. I've replaced a faulty 1.8 processor and the thing sounds like it's going to taxi across the room and head for the window.

Can anyone post a link to this software ? Please, for the sake of my ears.

Steve
 
now it's running quiet but still at 1.3GHz. :) my brother disconnected all fans and reconnected them one by one to see if it can work with less fans. seems like the G5 fans ignore the failsafe mode when the HD Bay fan is disconnected. still no 1.8GHz but a working machine without noise problems.
 
v-i-c- said:
now it's running quiet but still at 1.3GHz. :) my brother disconnected all fans and reconnected them one by one to see if it can work with less fans. seems like the G5 fans ignore the failsafe mode when the HD Bay fan is disconnected. still no 1.8GHz but a working machine without noise problems.
Click to expand...

Good to hear that is is working but hope that you will get the extra 500Mhz :rolleyes:
 
MacTruck said:
I thought all macs use the exact same motherboard. I thinks I is right!
Click to expand...
Now that they got rid of the iMac-based Single processor Powermac the number of boards dropped from 3 to 2.

The single processor Rev. B used a iMac chipset. U3-Lite & Shasta.

The Rev. B duals have a PCI-X and a PCI version, the PCI version lacks the PCI-X controller and taps PCI from the K2 controller.

The Rev As were all one board design and Apple populated them in various configurations. Single CPUs lacked the 2nd socket, and PCI versions just had a different jumper setting that limited the PCI-X controller to PCI speeds.

---

So that would be 4 major board designs total for the 2 generations of PM G5.

The Rev. B duals used 2 different memory controllers U3 & U3H, the Rev. C duals all use the U3H with the PCI version still deleting the PCI-X Controller.
 
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