For some time now I have been following the ThinkPad 600E CPU upgrade thread at http://www.wimsbios.com/phpBB2/viewtopic.php?t=4046&postdays=0&postorder=asc&start=0
, and have been fascinated by the longevity of the thread, and the amount of great information from sharedoc and many others - thanks to you all! When I came across this tread on upgrading the CPU in a ThinkPad 390E I decided to give it a try, since I had an old unit (2626-DOU, P-II at 300MHz) lying around doing nothing. These are my findings after modifying the FSB to 100MHz - please excuse the long post (which is my first in any forum!) but I wanted to give detail in the hope that someone might be able to suggest fixes for the problems that I have encountered.
I followed the directions given in rottenmutt's post, (plus the Cypress CY2285-2 clock generator chip's documentation he referenced), to get 100MHz FSB by pulling pin 14 high with a 10K-ohm resistor. After the modification the original CPU is reported by the BIOS as a Pentium II, 450 MHz! The system booted into Windows (98SE) OK, and WCPUID reports 100MHz FSB and the CPU to be a P-II at 450MHz! Sounds great, BUT ...
1) the floppy drive is not working - Windows Explorer shows a 5 1/4" drive, not 3 1/2" ??
2) USB is not working
3) serial port is not working
4) I haven't checked the parallel port, but the PCMCIA slots do appear to be working since a USB 2.0 card was detected OK.
The BIOS is at version R01_C9, the latest available for the 390E.
I have also tried a couple of other CPU's with this 100MHz FSB mod:
1) a P-III, 500 MHz (non-speedstep) - this is detected by the BIOS as a PENTIUM PRO, 500MHz, but the boot into Win98SE hangs! I tried doing a clean install of Win98SE with this CPU installed, and did manage to get into Windows with the default 640x480 video resolution. But after installing the NeoMagic AV256 driver from IBM all I got was a black screen!! I never did get it working.
2) a Celeron 466MHz - being designed for a 66MHz FSB I had hoped this might run at 700MHz, but no such luck!! In fact, NOTHING AT ALL other than the power-on light - no BIOS, no video!!
My lastest experiment has been to update the 390E's BIOS with the latest version for the 390X (ISB055WW), which takes the P-III CPU. The BIOS updated OK - after some fudging! (Initially the update program reported "This diskette does not support this system.", but I located where the model ID was being checked and changed the test value to be the same as in the 390E update program. Then, because the floppy wasn't working, I had to make a bootable CD of the update program in order to do the update!) With the 390X BIOS installed, the system runs the same as it did before with the P-II 300MHz CPU - i.e. the CPU is detected as a P-II at 450MHz, it boots into Win98SE and everything seems to work except for the floppy drive and the USB and serial ports. On startup the new BIOS does give a message saying "Re-work needed - using old RTC" but it continues to boot, or hitting F1 causes it to enter BIOS Setup OK. With the 390X BIOS the P-III CPU is now detected correctly as a "Pentium III, 500MHz", but the system still hangs on attempting to boot to Win98SE. And the Celeron 466 still gives NOTHING AT ALL!
I've learned a lot by reading this, and other, forum posts and would like to thank the many talented individuals who have shared their knowledge in these forums. But I'm strictly a 'follower' when it comes to these sorts of experiments with computers, and I've reached my limit! I'm hoping that perhaps some of the very talented individuals reading these forums may have suggestions on how to fix the problems I have identified with my 390E 100MHz FSB mod. Or might it be that the floppy, USB and serial ports on the 390E will not work at 100MHz FSB? (rottenmutt reported problems with his mod. 'on the table', but floppy and USB working OK when fully reassembled in the case; however that has not been my experience.)
One final piece of information. The 390E has no on-board memory, just two memory slots each of which can take up to 128MB of PC-66 memory according to the IBM website. I found that the original PC-66 memory worked just fine at 100MHz, but I also tried substituting PC-100 memory to see if that would make any difference; it did not! And I also found that - quite contrary to information on IBM's site - the 390E will take two sticks of PC-100 256MB memory for a total of 512MB, the same as the 390X!! In some forum I've seen a question about the maximum memory a 390E will take, and I can now say the answer is 512, not 256MB.