Well, the card works as advertised. No power issues at all with the 300W Dell PSU and I can run most games at reasonably high settings and get good frame rates for casual gaming, so quite happy from that perspective.
However, with the card being thicker due to bigger heatsinks + fans than my old HD3450, I noticed when I put it in that it sits right next to the southbridge chip and actually overhangs it a tiny bit. In typical Dell fashion , there was no heatsink on the southbridge, and probably barely room for one with the new card installed, so I thought I'd better install a monitor to check temps.
Idle temps:
With HD3450: southbridge idles at 50C
With HD5670B south bridge now idles 10 degrees hotter at 60C
CPU and northbridge temps pretty much unchanged
Temps under load: (While playing Assassin's Creed)
HD3450 - Southbridge temp hit 63 - a 12 degree C rise from idle
HD5670 - Temp hit 85C (a 25 degree C rise) pretty quickly, at which point I got concerned, stopped playing and opened the case to cool it off.
Aside from there not being a heatsink on the southbridge, I think the main problem is lack of fresh airflow on the GPU side of the case which is pretty closed of from the main part of the case due to the card and cables from the PSU.
By removing the blanking plates on bottom three expansion slots the idle temp with the HD5670 dropped 4 degrees to 56C.
I temporarliy mounted an 80mm fan on the outside of expansion slots to see if I could get the temps down more. Wasn't sure if I should have it blow in or out, so tried it both ways.
Blowing out: idle SB temp dropped to 51C
Blowing in: SB temp dropped to 47C
However, in that config the fan was way too loud. Too much of a pain to mod the 540s case as there is a wide stabilsation bar that goes front to back across the top of the cards and SB chip.
So - thinking about moving everything into a slighly larger, better ventilated micro ATX case - but if I'm going to do that, I may as well get a bigger PSU as well - which was the recommendation the first place.
Conclusion: while you can put a beefier graphics card into the Dell 540s slim case, it will cause the SB to run too hot unless you mod the case with an extra fan.
As mentioned, I'm going to go for a new case - still small, but wider with better ventilation, and a new PSU.
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For those who are interested, I'm looking at the following:
Case:
AOpen H450E micro ATX case
- Almost same DxH dimensions as the 540s which is critical as it sits under a desk, but is 20cm wide instead of 10cm.
- Takes an 80mm fan up front for air intake and a 12cm fan in back for exhaust.
- Side vents by cards as well as an Intel CAG 1.1 duct above the priocessor.
- Has enough 5.25 and 3.5 bays for my needs (DVD drive, Blu-Ray drive, card reader/fan controller in 3.5 bay, and 1x HDD).
Pic of inside of H450Y - exactlty the same as the H450E except different placement of front mounted USB/audio connections:
Details on AOpen site
here
I also need the system to be quiet as it's in the lounge (and I need to keep the wife happy), so:
PSU:
Cooler Master Silent PRO 600W Modular PSU. Good review over on
JonnyGuru where he gives it a 9/10.
Fans:
Noctua NF-S12B FLX - Case fan - 120 mm
Sharkoon - Case Fan - 80mm
Thanks to everyone who responded.
Kez.