Good thermal pads can be used. (But not the ones delivered with the cooler. They are quite poor).
Thermal grease is better because the layer should always be thinner than a pad.
I recommend low viscosity thermal grease (if you are from Germany you can use item no. "LEITPASTE 20GR" from
http://www.reichelt.de) and the "blob in the center" method. It is simple, quick and save. I use this method for testing new batches and never had any problems.
I've tried Arctic MX 2. It's better than Artic Silver 5, but I could not experience such a huge step like Chefnet:
or better cooling, my single went up from 204 to 220 with artic mx-2 under the cooler
... usually I get 4-8 Mhz more.
002-0: ztex_ufm1_15y1-04A347274B-1: f=200.00MHz, errorRate=0.00%, maxErrorRate=0.58%, hashRate=200.0MH/s, submitted 12 new nonces, luckFactor=0.99
002-0: ztex_ufm1_15y1-04A347274B-2: f=204.00MHz, errorRate=0.00%, maxErrorRate=1.52%, hashRate=204.0MH/s, submitted 17 new nonces, luckFactor=0.97
002-0: ztex_ufm1_15y1-04A347274B-3: f=196.00MHz, errorRate=0.00%, maxErrorRate=0.81%, hashRate=196.0MH/s, submitted 10 new nonces, luckFactor=1.03
002-0: ztex_ufm1_15y1-04A347274B-4: f=200.00MHz, errorRate=0.00%, maxErrorRate=1.18%, hashRate=200.0MH/s, submitted 19 new nonces, luckFactor=1.02
---
002-0: ztex_ufm1_15y1-04A347274B-2: f=208.00MHz, errorRate=0.00%, maxErrorRate=0.50%, hashRate=208.0MH/s, submitted 9 new nonces, luckFactor=0.96
002-0: ztex_ufm1_15y1-04A347274B-3: f=200.00MHz, errorRate=0.00%, maxErrorRate=0.62%, hashRate=200.0MH/s, submitted 11 new nonces, luckFactor=0.98
002-0: ztex_ufm1_15y1-04A347274B-4: f=204.00MHz, errorRate=0.00%, maxErrorRate=0.99%, hashRate=204.0MH/s, submitted 15 new nonces, luckFactor=0.96
002-0: ztex_ufm1_15y1-04A3476278-1: f=208.00MHz, errorRate=0.65%, maxErrorRate=3.22%, hashRate=206.6MH/s, submitted 18 new nonces, luckFactor=0.96
@Chefnet: How do you apply the grease? A blob in the middle? How much? Moving the heatsink around, or just pushing it down?
The one problematic board still sucks. Hashrate went up:
002-0: ztex_ufm1_15y1-04A3476278-1: f=200.00MHz, errorRate=0.87%, maxErrorRate=1.00%, hashRate=198.3MH/s, submitted 14 new nonces, luckFactor=0.82
002-0: ztex_ufm1_15y1-04A3476278-2: f=196.00MHz, errorRate=0.23%, maxErrorRate=0.55%, hashRate=195.5MH/s, submitted 16 new nonces, luckFactor=0.88
002-0: ztex_ufm1_15y1-04A3476278-3: f=196.00MHz, errorRate=0.00%, maxErrorRate=0.81%, hashRate=196.0MH/s, submitted 13 new nonces, luckFactor=0.83
002-0: ztex_ufm1_15y1-04A3476278-4: f=192.00MHz, errorRate=0.11%, maxErrorRate=0.50%, hashRate=191.8MH/s, submitted 10 new nonces, luckFactor=0.95
---
002-0: ztex_ufm1_15y1-04A3476278-1: f=208.00MHz, errorRate=0.81%, maxErrorRate=3.22%, hashRate=206.3MH/s, submitted 16 new nonces, luckFactor=0.96
002-0: ztex_ufm1_15y1-04A3476278-2: f=204.00MHz, errorRate=0.26%, maxErrorRate=1.20%, hashRate=203.5MH/s, submitted 17 new nonces, luckFactor=1.06
002-1: ztex_ufm1_15y1-04A3476278-3: f=204.00MHz, errorRate=0.04%, maxErrorRate=3.01%, hashRate=203.9MH/s, submitted 15 new nonces, luckFactor=0.98
002-1: ztex_ufm1_15y1-04A3476278-4: f=196.00MHz, errorRate=0.00%, maxErrorRate=0.56%, hashRate=196.0MH/s, submitted 10 new nonces, luckFactor=1.06
...but No.4 still is below 200 Mhz and I'm getting FPGA-shutdowns (5 times since yesterday):
002-0: ztex_ufm1_15y1-04A3476278-1: Error: Hash rate drop of 5.8% detect. This may be caused by overheating. FPGA is shut down to prevent damage. 51.99384114688102: Device disabled since 2012-05-02T03:05:59
002-0: ztex_ufm1_15y1-04A3476278-2: Error: Hash rate drop of 5.4% detect. This may be caused by overheating. FPGA is shut down to prevent damage. 51.772818289686384: Device disabled since 2012-05-02T02:57:22