Last night I ran a "Thorough scan" as defined by avast. Typically I do a standard scan, and that is the type of scan I would run as a benchmark to measure how long it takes avast to run. And I will do this eventually...but for now, here is what happened:
I started the thorough scan at 9:47PM. By 9:53PM about 22K files were scanned. At this point (and coincidentally) the Apple iTunes folder was being scanned. The scanning slowed down to one file at a time. This continued for about a half hour. I stopped watching after about 45 minutes, but rechecked later, and by 10:53, about 34K files had been scanned. At this point, I pretty much fell asleep at the wheel and I cannot tell how long it took to complete the scan, but when I checked this morning, 26.3GB had completed scanning and the process was complete. In the past, I have noted roughly 130K files are scanned (but this is with the standard scan). While I was awake, I did monitor system performance, and my CPU was hitting 100% utilization frequently. About 66% of the RAM was in use, and "ashSimpl.exe" was the program driving the CPU usage from what I could tell (I assume that's Avast using ashSimpl?).
In summary, I concluded that my CPU is likely inadequate to handle the load demanded by Avast. If newer releases of Avast have been optimized to run a a dual thread CPU, by elderly Pentium 4 is slower and has much less L1/L2 cache so it is my number one suspect.
As far as RAM goes, 512MB is a respectable amount of RAM for this vintage notebook (I have a Compaq laptop, same age that has 256MB installed, and I have an IBM T-41 that has 768MB RAM installed, so the 512MB in this laptop seems in line).
In addition, the HDD led was pretty well lit up through the process. I had done a defrag right before scanning, and only about 40% of my HDD is used, still the HDD seemed to be laboring. Surely today's SATA HDDs are able to outperform my older PATA, maybe 4200rpm drive.
Maybe its just time to retire my older laptops. Now that I've been exposed to my wife's Core 2 duo, with 2GB RAM and a 5400rpm SATA drive, I will always feel hobbled with this present equipment.
I will rerun a standard scan now that I got some sleep, and report results on this thread.