My 2p worth, for what it's worth.
Very interesting Alan.
I very rarely delve deeply into the setup.log, only taking a cursory look at it. Your observations are totally correct in the use of the /limitcpu parameter. I have recently cleared out my setup.log file and there was only 56KB so doing a search for /limitcpu only gets one hit and that was on the 23rd and I have had a number of updates since then. This however doesn't seem to be a VPS update but news.
So it would appear that some updates have also got past without this limitation. My Update (Basic) settings have the Virus Database set to 'Ask' so I get notification in the form of the pop-up at the bottom of the screen and I usually click that when it is displayed to do the update.
I don't know if that 'Ask' would be classed as a manual update or not (as it is initiated automatically), but if so then I wouldn't have had the single /limitcpu entry from the 23rd either. Even then I'm not sure if that single entry was for the VPS update as the command line didn't have that in it rather it had /updatenews, see below.
I did a manual update and did a screen capture of the Task Manager that shows avast.setup at 97%, giving an overall of 100% with Task Manager taking 2% and something else taking the remaing 1% to make up the 100% cpu. So on manual (and possibly 'Ask') the avast.setup happly gobbles up what ever cpu is available. During this time there is a noticable slow down in browsing, etc. but for me this isn't for that long as a) I don't have big gaps in my VPS update cycle.
Auto ? - general Cmdline: /downloadpkgs /noreboot /updatenews /verysilent /nolog /limitcpu
Manual or Ask ? - general Cmdline: /downloadpkgs /noreboot /updatevps /silent /progress
So there are other differences to the command line other than the missing /limitcpu. This difference could mean even though you have selected 'Ask' this happens automatically regardless, hence the /verysilent parameter.
Unless it is Alwil's thinking that when launching a manual update there is no need to limit the cpu activity as would appear to be the case with Igor's response. As for the comment:
It's normal for a program to perform whatever it's asked to in the usual way, using as much CPU as needed (there's even no documented way to limit one's CPU usage, as far as I know - it's kind of a trick here).
What would be wrong with applying the same trick, /limitcpu to the command line for the 'Manual' or 'Ask' form of updates.
