Mods
It is possible to use Pentium III CPUs in the ThinkPad 600E. It does however require a little more than just popping in the MMC-2 module and firing it back up. The highest specification PIII CPU you can use is the PIII 850MHz.
The ThinkPad 600E has a Pentium II motherboard; as such it doesn’t quite know how to handle Pentium III architecture. That was the bad news. The good news is you can work around this with good results. After installing the new CPU the first time you power on you will receive a POST error 127. You need to hit ESC and F1 a bit to bypass the error and get to the BIOS settings.
Error 127 is cause because the BIOS does not know how to initialise the Level II cache on PIIIs. Get into the setup menus and click CONFIG, once there hold ctrl-d to open up a hidden hex editor. From here we can disable the Level II cache routines altogether. Move to b yte 20 and change the value of 02 to 0A. Hit F2 to save the change then power off the ThinkPad. It is important that you power off, a reboot does not apply the change. You will now be able to boot without the error 127.
Note: Some people have experienced instability after upgrading to PIII CPUs caused by the onboard RAM. When you install a PIII CPU you automatically increase the FSB to 100MHz which can be too high for the 66MHz specification memory. You can disable it in the same manner as the Level II cache by setting byte 2B from its original value of 80 to 81.
Anytime you use the Initialize function in the Easy Setup utility will undo these changes and they will need to be reapplied.
So now we have a CPU running with no Level II cache. Thankfully there is a work around. It is not perfect and people are working on a patched BIOS to permanently fix this problem. For Windows a small application called Powerleap can force the Level II cache to enable at start up. It can be found here: http://hnpy.onlinedown.net/down/PLeapCCP_V5_1_0_0_1.rar
Set it to force the Level II cache and auto load at startup.
There are a couple of utilities for Linux mentioned in this thread: http://www.wimsbios.com/phpBB2/viewtopic.php?t=4046&postdays=0&postorder=asc&start=0
I have no experience with them. Please feel free to email me katch@xabk.co.uk your experiences and I will add your information to the site.
FSB Mod
It is possible to mod the motherboard to increase the FSB to 108 MHz giving a stable 8% overclock. It is necessary to open the ThinkPad and remove the MMC-2 Module. Then on the left of the socket you need to carefully solder a 1k ohm resistor from the lower end of condenser C21 to the right side of resistor R164.
Fig.1 - Resistor placement
When you reassemble make sure the resistor does not short against any part of the system board or the MMC-2 module!
Your system will now run at 108MHz FSB. Some people got instability from the onboard RAM at this stage. Refer to the end of the PIII CPU installation guide for details on how to disable it in the BIOS. I personally have never experienced this instability with my ThinkPad’s onboard RAM.
Speedstep Mod
The majority of Pentium III MMC-2 processors use a technology called Speedstep to throttle down the CPU speed when demand is low. Unfortunately this technology requires a motherboard that supports it. There is however a way to mod the CPU to automatically run at the higher speed.
With the MMC-2 module removed from the laptop find the Speedstep controller chip. It sits on the underside of the module (refer to pics). You need to cut the track from the 4 th pin in from the lower right of the chip just before the first dot.
Fig.2.a - Step 1 on earlier CPUs 500MHz - 700MHz
Fig.2.b - Step 1 on later CPUs - 750MHz - 850MHz
To complete the Mod refer to the correct picture for your CPU and solder a 2.2k ohm resistor as indicated, again being very careful upon reassembly that the resistor does not short against and part of the module.
Fig.3.a - Step 2 - Resistor placement on earlier CPUs - 500MHz - 700MHz
Fig.3.b - Step 2 - Resistor placement on later CPUs - 750MHz - 850MHz
To ensure the CPU starts at the higher frequency cover the cooler vent while powering on. Without covering the vent the higher frequency only activates about 30% of the time. The cause of this is being investigated and is thought to be heat related. If a better solution is found you will find it here.
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