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?
hmm maybe you should copy my 8vrm board then
i have to stick my ear next to it to hear a faint buzzing....tiozes: ppl been having problems going from 1.0 to 99.1 tune or i think any tune...should go back to 99fw then 99.1 tune