OK it's Morning in the UK so I am going to have another go at wrapping my head round what's going on with this Not So Lite S7? Excuse me while I think and Type, this may or may not lead anywhere?
![Smiley](https://bitcointalk.org/Smileys/default/smiley.gif)
So here's the guts of the post from carlosmnk in the other thread that suggests 135 chips.
This contains an error, they put 45 chips per hasboard, total 135 chips, not 145:
batch 1, 3 and 5: 4860 / 162 = 30 (total hashpower / number of chips = hashpower per chip)
batch 6: 4050 / 30 = 135 (total hashpower / hashpower per chip = number of chips)
So, they went from 54 chips per hashboard to 45 chips per hashboard.
If you just look at the maths, the case for 135 chips is spot on, with the Hash per chip dividing down from 4.86TH with 162 Chips to 30GH and the multiplying neatly back up with 135 Chips to 4.050TH.
So what's the problem? Well the resultant Core Voltage on the Chips is the problem....
If we go back to the 4.86TH system, then 162 Chips are divided onto 3 Boards giving 54 Chips per board giving a Chain of 18 Nodes with 3 Chips / Node. Apply 12V to the 18 Chip string and we get 0.667V which is bang in the middle of the Core Voltage range shon in the BM1385 Data Sheet.
![](https://ip.bitcointalk.org/?u=http%3A%2F%2Fwww.slotforum.com%2Fforums%2Fuploads%2F1446669741%2Fgallery_2150_2322_4107.jpg&t=665&c=uqKR4Pkdn2uiqg)
Now if we look at a 135 Chip System, then that has to be 3 Boards which gives 45 Chips per board and the only way that can be divided up is with a Chain of 15 Nodes with 3 Chips / Node. Apply 12V to this string and we get 0.8V which is off the chart.
It's actually right up at the Max Recommended Core Voltage, but not over the Absolute Max so perhaps it's OK?
That is until you look at the new PSU spec which is "Rated Voltage: 11.60 ~ 13.00V" Now if we apply 13V to the 15 Nodes we get 0.867V so yes still under the absolute Max but over the recommended.
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![](https://ip.bitcointalk.org/?u=http%3A%2F%2Fwww.slotforum.com%2Fforums%2Fuploads%2F1446669741%2Fgallery_2150_2322_76174.jpg&t=665&c=xTX-6BKednRZmQ)
The other "problem" is the W/GH efficiency. At the original 0.66V we have 0.219W/GH add say 14% to that for the PSU & other inefficiencies and you get to the rated 0.25J/GH
However take a guess at the W/GH for a 0.8V Core, say 0.3W/GH and even without adding the 14% you can see we are way off???
So what's going on ? Well assuming this is a 135 Chip system with 15 Chip tripples per string my only thought is that the Data Sheet must be wrong and in practice the Core voltages needed are more like those for the BM1384 used in the S5 which coincidentally has a 15 chip string?
So no firm conclusion, overall 144 Chips works out best if the BM1385 Data Sheet is correct, however 135 chips fit's the maths best, but in that case the Data Sheet has to be wrong. Makes you wonder if there is a third solution waiting to be found?
Let's hope that someone will take the case off and post a photograph?
![Smiley](https://bitcointalk.org/Smileys/default/smiley.gif)
Rich
UPDATE. The Bitmain Website has been corrected and now shows 135 Chips. So that part of the mystery is solved. What is not solved is the Chip Core Voltage and reconciling that and the J/GH with the BM1385 Data Sheet?