Posted by Deliverator on April 3rd, 2006
I’ve heard from many PPC owners that the Xscale series of processors are often very conservatively clocked. Most PDAs don’t need a whole lot of processing power for the tasks they perform. I believe that the first couple generations of palm pilot, for instance, were 16mhz Motorola processors, and almost all the applications I used to run felt quite snappy compared to their PC equivalent. Today’s PDAs seem to be clocked at between 300 and 600 mhz and are almost universally Xscale/Strongarm processors at this point. My needs are a bit more demanding than the typical PDA user, so I decided to see if I could overclock the Xscale PA255 processor in my Netbook Pro a bit. I managed to find a overclocking utility for the Xscale processor. The application is in japanese, but is fairly self explanatory, and full source code is included, so it should be possible to create an english language version. The application was designed for the NTT Docomo Sigmarion III, a japan only HPC that has gained a cult international following despite the japanese only Win CE OS version. The utility works fine on my Netbook Pro and is reported to run on the NEC Mobilepro 900c as well.
After some mucking about with the utility and some nominal overclocking just to test that the utility was actually working, I decided to put my Netbook Pro through its paces. I gradually increased the clock speed and benchmarked and looked for signs of instability at each progressively higher clock speed. I ran timedemos in quake, a video benchmark using TCPMP, ran the BMQ benchmark suite and calculated PI out to a rediculous number of digits. All the while I watch for signs of overheating (visual artifacts, hotspots of the case, weird smells, smoke, etc.) and found none. I also checked to ensure that the Netbook Pro’s CF, SD and PCMCIA slots were working properly. On my Strongarm based Jornada 720, I found I could overclock the unit, but that the expansion slots would stop working, rendering any overclocking of limited utility. On my Netbook Pro, I had none of these difficulties and was able to stably clock the unit to ~800mhz, double the units manufacturer clocked speed!
I am not sure how badly battery life would be impacted at this extreme speed, but I noticed no stability issues while running at this speed. General system navigation was perceptively snappier, and every quantitative indication of performance increased substantially. BMQ returned very high scores, with only an overclocked Sigmarion III scoring higher overall, due to its dedicated video processor. I would like to plant a thermistor on the CPU and get temperature readings at different speeds before overclocking on a more or less permanent basis, but am a little wary of cracking open my rather expensive Netbook Pro. All in all, I am quite impressed with the overclocking potential of the Xscale processor. Not since the mid 300 mhz Intel Celeron processors can I recall a processor that so easily overclocks to nearly twice its default clock speed.