When I first bought my R31 last month, it came with a 1.06GHz Celeron Mobile, and while usable I found it quite easy to hit its limits, especially when web browsing with a few hefty tabs open. I did a bit of research and easily sourced the flagship processor for the model, the 1.13Ghz Pentium III Mobile (SL5CK). A bit of money thrown at Ebay and I had a processor within a day or two, and since I wanted to change the CMOS battery anyway it seemed a good opportunity to dismantle it.
Dismantling is pretty straightforward if you use the Service Manual, although the keyboard bezel has plastic hinges which don't look like they'll take a lot of abuse. If yours is anything like mine, the heatsink will certainly need cleaning and new thermal paste applying. Once the heatsink is out of the way, changing the processor is as easy as on a desktop.
The performance difference is pretty impressive. Multimedia is marginally better, but tasks like web browsing are an awful lot more civilised, scrolling is a lot smoother and it doesn't feel anywhere near as sluggish to use as the Celeron. Considering that the SL5CK doesn't cost much second hand, I'd definately recommend it.
[ThinkPad Roll Call] T61 (FreeBSD) - X60 (Arch Linux) - X40 (Arch Linux) - A31 (FreeBSD) - 600E (FreeBSD) - A21p (FreeBSD)
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