I will start with a warning. It is unknown if this is safe. KnC may have turned off the VRMs due to that there is a problem with the design.
You board might burn! On the other hand they ran with all VRMs turned on for a few weeks when they were new without any major issues.
I have run a few machines with 8VRMs for almost 2 weeks without problems. Some machines will start buzzing pretty loud, I have no idea why.
bondus thx !
Is the buzzing 1 VRM, ALL VRM's, or just a few?
DISCLAIMER:
I have Oct 4 VRM hardware.
I have extra VRM's(and associated parts) that I thought to install, that is why I have studied it.
At this point not cost effective, at over .25 BTC ( >USD$125 ) per ASIC in VRM's alone.
I have 'ideas' why 8 VRM's MIGHT misbehave.
(notice the lack of absolutes in the above sentence!)
** Massive text with ideas to explain buzzing and safety ***
Too bad I do not have access to a proper electronics lab
Most of your ideas could be easily tested with a scope and some other basic tools.
But I have made some other observations that might be interesting:
Iout and Vout from the two VRMs in the pairs are not even.
Typical values (as reported by the VRMs):
table]
| VRM Nr | V | A |
| 0 | 0.8154 | 24.8750 |
| 1 | 0.7998 | 27.6250 |
| 2 | 0.8066 | 30.3125 |
| 3 | 0.8164 | 26.8125 |
| 4 | 0.8184 | 30.5000 |
| 5 | 0.8096 | 30.0000 |
| 6 | 0.8235 | 27.6250 |
| 7 | 0.8164 | 31.8750 |
0,3 and 6 have slightly higher voltage that the other VRM in each pair. The pair 4,5 is pretty even.
Current is a bit higher on the VRMs with lower voltage. It looks the same on many different boards.
You would expect voltage and current to be the same on both VRMs in a pair. Odd.
The buzzing gets louder the more power you use. You can clearly hear when a block is found
I haven't had time yet to open a box and check what VRMs are buzzing.
Since you have ordered the parts you must know the value of then RTUNE and RTrim resistors for the VRMs?