I have had a similar "problem."  I too had the CPU report at 1.2 on my 2.0GHz Inspiron 8500.  However that was just on boot before I loaded any applications, so the system was essentially idle.  I mean I don't really know but it seems that whenever I lot a fairily resource intensive application that it shows it running at 1.99GHz, even Internet Explorer seems to kick it up to the top speed.  See what I think is that once the processor usage goes up to max, which it always does with Internet Explorer, it jsut adjusts the system clock accordingly.  This might have also been before the update for the SideStep support for WIndows XP, but I'm not quite sure.  I think that your computer if working just fine, just need to understand more about how it determines whether or not to be running faster.  I personally didn't see any option for disabling SideStepping, which is what I want to do, I always plug it in I just carry it around with me everywhere.  The option to disable it in the BIOS says that it will make the CPU run at the lowest state possible I think, maybe you should look at it again.  But, like I said I'm no expert.

Hope this was helpful.

I have a Inspiron 600M, that has developed a really weird issue when playing "GTA Vice City" Here's how I reported it to Dell:
Problem Description:
While playing the game "Grand Theft Auto - Vice City", I have run into a highly unusual problem that wasn't present during early stages of the game. When attempting to load my saved scenarios of the game, with the machine on AC power, my 600m will not complete the software loading and simply stops with a black screen. However, if the machine is unplugged from it's AC adapter and allowed to run on battery, the loading of that saved game completes itself. The problem is resolved completely when running the game in the battery mode. In other words, There is a definite issue where the game runs fine on battery power, but something is preventing correct software loading of the game when the 600m is on AC power. I have double-checked all of my power management settings and don't see anything that should cause this. I have also downloaded all of the latest drivers, which didn't affect the problem either way. I have no other problems with my 600m in any other applications, in either AC or battery.

Dell support seems to think it is a hardware issue with the power adapter. I suppose it's worth a try to swap the adapter, but it seems more like a power management issue. Anyone care to take a shot?

I own an 8500, with exactly the same issue. Let me ask you a few questions, and we'll compare notes.

If you use the Always On setting in Power Management, does it perk up and stay at higher than 1.2g?

If it doesn't, do you notice a sudden 4-second burst of fan activity on the left rear of the system, then no more fan activity at all, for the entire session?

If you enter Setup using F2, does it report the CPU speed as your max CPU speed, for about 4 minutes, then give that odd fan burst I described above, and then report 1.2g, for as long as you care to watch it?

If you set the system over an AC vent, does the system start behaving normally, at the higher CPU speeds, both in Setup and in the OS?

If all of these apply to your machine, there's a problem with the way the CPU is being cooled, and the Pentium 4 chip is throttling down to save itself from thermal destruction.

The cause? On mine, it wasn't the fan or the heatsink. They were replaced and the problem remained. We swapped CPUs with another P4, and the problem followed my system, and my CPU worked fine in the other machine. That leaves the motherboard in my system as a cause.

What tipped me off to this? On a hunch about the thermal issue, I put the machine over the vent, and it fixed it. So I swapped the fan with the fan from another 8500, and it had no effect. So I booted to the Drivers and Utilities CD, and ran the CPU fan diagnostics, and it failed. A lot of folks, thinking this is a CPU issue, run just the CPU diagnostics, and they pass, because it's doing exactly what it's supposed to do. They then turn to Windows XP, and start digging in there, and end up blaming the OS.

Set it over an alternate active cooling source. If it normalizes behavior, then boot to the D&U CD (using the F12 boot menu), and run the CPU fan diagnostics, from the Custom menu. If it fails, contact Dell, and detail the steps you've performed. If they want you to take a cooling fan first, go ahead and try it, and ask the technician to take ownership of the issue, so you can inform them of whether or not it fixed it. But if that doesn't fix it, then explain that the only part left that could cause it is the motherboard.

Good luck. I'm waiting for my motherboard replacement.

I have to agree with you, they finally replaced both cpu and motherboard and the problem has now gone.

In some cases it might be able to be resolved without the ordeal of replacing a motherboard - I saw this fix on the forum here - http://forums.us.dell.com/supportforums/board/message?board.id=insp_power&message.id=19124 - and it worked for me also. It's worth a try, since it only takes a moment. Makes me feel kinda stupid for all the time I spent reinstalling my OS and apps etc...

Yes, I've been getting this issue as well. I run SpeedswitchXP and I8kfanGUI and they report that the CPU speed drops down to 600 MHz from 1.7 GHz after playing for some time. Even if I had the Speedstep settings to Max Performance it will still do this. When I looked at the temperature graphs in I8kfanGUI, it shows that the CPU, HD, and RAM temperatures were going constant for a while, then the CPU speed all of a sudden just falls straight down to 600 MHz. I'm on the A08 BIOS of the 600m.

I have the same problem on a D600 playing Counterstrike.  Sometimes it will drop from 60 fps down to 10 fps roughly every 10-15 mins, caused by the cpu throttling down to 600 mHz, but other times it only does it after an hour or so.  After a few minutes of slowness, it will jump back up to full speed, but it gets very annoying.  I can never see how hot the cpu is while im playing the game, but when I quickly exit, it reads ~120-130 F, and from the graph in fangui I can tell that the temp stayed ~150F for awhile, then the speed suddenly dropped.

However, what I don't understand is why it only does this with Counterstrike, as I've seen it go up to 161 degrees encoding video, and it still stays at 1.6ghz

Also, if this can't handle playing Counterstrike/halflife in January without overheating, how is it going to do with Half Life 2?

Thanks,

Mike

I think I was able to get the answer from another post. I had to actually downgrade my BIOS from A08 to A06. I have never had the problem since. I played Lord of the Rings: Return of the King for hours on end and I never had the problem since. Maybe it is a combination of the CPU temp, GPU temp, DIMM temp, and Hard drive temp that causes this to occur. Encoding video does not really tax the GPU, unlike playing a game.

I think it has to do with the CPU temp. I noticed that I got lag during games after awhile and when I checked the data I found that my cpu would reach 71 degrees and then automatically switch to half speed to cool down regardless of being set to max performance by speedswitchXP. All I did was blow through the bottom vent until i collapsed from dizzyness and now my laptop never gets past 63 degrees and everything runs smooth.

The slow down seemed to be caused by the cpu auto-switching to a lower speed because of heat. Although the intel website says my perticular cpu can take up to 101 degrees so I don't know why it would have a safety measure at 71. Either way it runs fine now.

Hey what a good idea...blow statically charged dust all over the innards of the machine...  I don't think so!...Far better to remove the case and clean the fans etc off properly taking the usual ANTI-STATIC precautions when touching static sensitive parts such as memory sticks, CPU's mobo chips etc etc etc