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Author Topic: ASIC engines, BGA reflow  (Read 1593 times)
soy
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September 29, 2013, 01:49:03 AM
 #1


Some ASICs are hamstrung with non-working engines but hash away with a lower output.  I understand a little about the ASIC assembly, such as the chip gets soldered to conductors that pass to the balls of the ball grid array.  Reflow of BGA Nividia graphics chips on Presario motherboards is a classic case of saving a motherboard with a little skill, heating the solder under the BGA to reflow where opens may have occurred.

Has anyone tried increasing the number of functional engines of an ASIC which is in place, e.g. heating the ASIC to 400°+F for some minutes or putting a miner board in an oven to reflow the ASICs and if so has it improved the mining capability of the miner?

Thanks.

                               
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September 29, 2013, 04:18:16 AM
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I have a feeling the bad hashing engines are related to manufacturing defects in the actual ASIC chips themselves, not in the mounting to the PCB.  I don't know much about ICs and reflow though so that's sort of a guess.

But it's certainly an interesting idea... maybe we'll see people trying it once more miners achieve positive ROI.
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September 29, 2013, 05:32:30 AM
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I have a feeling the bad hashing engines are related to manufacturing defects in the actual ASIC chips themselves, not in the mounting to the PCB.  I don't know much about ICs and reflow though so that's sort of a guess.

But it's certainly an interesting idea... maybe we'll see people trying it once more miners achieve positive ROI.
Ya I'm gonna agree with you here. I'm no EE, nor do I have much experience in reflow repair, but it was my impression that reflow was only necessary if A) The original chip placement was done incorrectly, or B) time and wear/tear caused cracks in the solder, and needed to be repaired.

Neither one of those would account for a non-working or partially-working engine in a BFL chip.

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September 29, 2013, 10:18:38 AM
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These nvidia chips had a problem with the underfil that would expand/contract too much after a lot of thermal cycles, causing the solder bumps that connect the die to the substrate to crack over time. Those are not the solder bumps underneath the chip, they are "internal":


Reflowing would sometimes help revive dead chips.

But thats not whats going on with bitcoin assics. Dysfunctional hashing engines within a chip are just a result of die defects during the manufacturing. They are unavoidable. Faulty engines are just disabled to salvage the rest of the die. The same is done with CPU's and GPU's that usually have spare "cores", spare L2 cache etc so that some defects dont render the entire chip useless. Reflowing wont do a thing here. Flashing the BIOS may help if the disabled cores were disabled for economic/marketing reasons rather than for being actually defect, like many AMD GPU's and CPU's, and indeed the BFL jalapeno I believe.
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