Underclocking in a HTPC setup

I've got a spare 2.4B PIV and a spare XP2500+ Barton (locked :( ). I'm planning on using one of these cpu's in a HTPC setup. In order to get a totally silent box I'm thinking that the cpu could be underclocked to reduce voltage/heat/cooling requirement. I don't need any great processing power. I've no experience of underclocking and would welcome anyone's views on this. Which of these two cpu's would be a better candidate? I also need to find a micro-atx motherboard with onboard graphics and would like to know if anyone has any recommendations.

how about going selling both and getting yourself an a64 3000. IF you dont need the processing power it will run in cool and quiet all the time and them if you do need the extra little oomph it will be there?

they are perfect for this environment.

Nice idea, but I want to keep both these cpu's as they are 'spares' for my two systems listed below.

The problem you are faced with is that if both CPU's are multiplier locked then you will have to lower the FSB. This is bad for overall system performance.

Either find a CPU with an unlocked multiplier, or just try finding the lowest stable voltage for the CPU.

I'd say go for the P4 and try undervolting.

Or get another mobile barton. Extravigant I know, but they are well known for their underclocking abilities.

I have undervolted my P4 in my shuttle to 1.3V, the temperature drop was a nice 6 degrees! Im sure you can do the same with your cpu. Also lowering the fsb is definately a possibility if you dont need performance and just want to do easy tasks like watching dvds etc.

you could lower the fsb to speeds the same as an XP mobile. I think this would give the same performance as having an XP mobile. Please correct me if I am wrong though

go for a XP1500M or a XP2500M after you sell those older processers :D

Have either been run before? If not - dont even boot them at higher voltages as that'll reduce your undervolt.

Reducing speed doesn't actually help an undervolt - I have seen overclocks performed better with undervolting than at stock.

Both cpu's have been overclocked previously. I'm inclined to go for the P4 though I guess I could swap the XP2500+ for the unlocked mobile XP2500+ in my gaming system, then use the unlocked cpu in the htpc - seems a bit of a waste though!

Just set the locked Barton to 133FSB for 1.47GHz. At that speed it wouldn't surprise me if it'd run on 1.3V or less- I could easily run a Tbird at 1.6GHz with 1.4V- it ran just a few degrees over ambient with an X-Dream on it's lowest setting:). At that speed you'll have power to spare for any HTPC application short of real time MPEG4- re-encoding or whatever.

Your only problem would be if the board doesn't support voltage adjusdtments- AFAIK the locked bartons can't have their voltage adjuisted by pinmodding:(.

Rich :¬)