A20m "Successful" 600-900 MHz upgrade and freezing

[Harbinger]

I was able to "successfully" upgrade my A20m from a 600 MHz to a 900 MHz CPU, and run the unit without problem for a time. Last week, however, my laptop seemed to develop the 'black screen, no POST, no boot" problem described by many others here on the board and elsewhere. I fixed that problem, and in doing so may have found a solution for it but I'd need more people to test.

First, the success story. I determined which CPU my unit had and ran a program to test the BIOS and let me know which CPUs it would recognize and still boot up. The result of that test told me that the machine would recognize a CPU with an internal code of 0686. Next, using the FSB speed (100) I determined that the original CPU must be using a multiplier of 6 to get its original 600 MHz speed. After visiting Intel's Processor Finder (on their website) and determining which chip package I needed I then compared Mobile Pentium III CPUs with the appropriate package, multiplier and internal code. I found that a 900 MHz processor with a stepping code of SL59J would work, so I bought one from eBay.

I knew the stock heatsink wouldn't be beefy enough, so I spent time with the Hardware Maintenance Manual. I found that different models of A2x machines with faster processors had different part numbers on their heatsinks. Also, those units had an additional part mounted to the heatsink, called a "heatpipe hinge (lower)." The next question: what and where was the upper part of that component? I finally discovered that there's an additional aluminum heat plate in the LCD cover assembly that mates to that heatpipe hinge. I bought the heatsink/fan, heatpipe hinge, and used upper cover online from some IBM surplus parts dealers. Total cost of all the pieces/parts: about $60.00.

I put the pieces together and turned the unit on. It worked! I ran it for several hours the first day with no lockups. Ran it a second day for a longer period with no problems. The third time I went to use it, WIndows XP loaded and froze. When I powered the machine off and on again, boom! The dreaded black screen appeared.

I read a number of posts here and there, with people pointing to one or another solution. Some replaced the two surface-mounted power management chips. Some replaced the CMOS battery. Others disconnected the CMOS battery, main battery, and main power then held the laptop upside down and depressed the power button anywhere from 2 to 2000 times. None of these worked for me.

I was about to strip the laptop down to the mainboard and replace any surface-mounted electrolytic caps I found around the power management chips first, but got an idea: what would happen if I stuck the original CPU back into the unit? Well, that worked. The laptop is again functional but at its original 600 MHz speed.

I'm just wondering if some of these failures are due to faulty CPUs? Did my mod fry the CPU, or did it just choose to die at that particular time without any help from me? I need to try and find another SL59J on eBay, but it took a good two months earlier on to find a listing for one at a decent price.

I just thought I'd pass this along...perhaps some of the readers of this post can borrow/find/steal another CPU to try in their failed laptops?

[STSinNYC]

Sorry to read about your struggle with the CPU upgrade. I have an A20m, model 26284SU, which I upgraded from a P3 700 Mhz to a 1 Ghz with no problems. I don't have a high level of technical knowledge about the motherboards, so these questions may not help. You have the latest BIOS? The original 600 Mhz processor is P3, not Celeron?

Hope you can work it all out.

[Harbinger]

The laptop is a 2628-4UU, and the processor is indeed a PIII. I had loaded the latest BIOS available on the IBM/Lenovo web site (v1.13).

At this point I'm glad it was just the processor and not the mainboard. The unit's still usable but slower. Oh, well.