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Archive for the ‘Litecoin’ Category

Xilence PSU really are quite poor quality.

16 Apr

So today I went out and purchased a couple of Xilence PSU (XP500), specifically because they were rated at 30.0A at 3V3.

We needed a fairly strong 3V3 supply rail to feed a couple of maxim buck converters down to 0.98v for an FPGA project.

You would think that 3V3@30A would be able to handle such a simple situation.

Well you would be dead wrong..
After loading the PSU upto 6A the supply rail dropped to 3v1 we then added another 6A load and the rail hit 2V98 Also the 12V rail began to sag down to 11v8 volts and the 5V rail hit 4V8, even with no loading applied to anything other than the 3V3 rail.

Considering these supplies are rated at 3V3@30A, we should not see such poor power degradation with what is basically a 12A loading on the 3V3 rail.

By the time we were at 18A@3v3 the 3v3 rail was below 2v9 and the 12V rail was also in decline.

Furthermore the power supply started to make a sound as if there was a screw loose in the cooling fan, removal of the load caused the sound to disappear.
I’m of the mind that something was breaking down inside the PSU whenever the 3V3 supply was loaded.

OK fine let us contact their support…
After finally getting their support system to accept the email request and supplying the PSU serial number
I STILL have NOT had a reply after 7 Days….

Is the quality of the Xilence PSU bad or is the application unsuitable?
Well, to put this in perspective, I also purchased a really shitty Chinese made ATX-320T PSU that claims it can supply 3v3@14A, this thing cost less than $11USD(I kid you not)
After 4 months at an overload of 18A@3v3 the supply rail on the Chinese PSU has dipped down to 3V2 the 12V rail is at 12V2 and the thing is still as quiet as a whisper, plus no magic blue smoke daemon has appeared.

Recommendation
Do not EVER buy Xilence PSU’s, it may even be better to purchase that shittly little Chinese brand after all.

Conclusion
Xilence PSU’s appear to suck ass so badly that you would NOT want one inside your computer.
By the way their internal build quality on the PSU is basically ‘Fucking abysmal’, parts of the inline filter are ‘flapping about’ in the air as if it was an afterthought needed to pass the EMI standards.
Whilst there may be many Xilence the market, such poor power regulation can only lead to seriously stressed computer parts and early failure of equipment.

Time to return this Xilence crap to the shop and save some serious money.

 

Bitcoin: A revamp of our XUPV5-LX110T FPGA mining rig (now faster)

02 Apr

Since the ASIC order went tits up at Tom’s ASIC fuckfest and BFL STILL have not delivered product, we spent the time working on our existing FPGA miner.

Improved in every way
Xilinx development boards are actually very good and it is a testament to the design of the Power-supplies that we managed to push the Bitcoin mining design to 200MH/s ,But why was the board consuming 47W when hashing hit 200MH/s?

The secondary issue was why the logic would not go faster than 200MH/s, even with improved FIFO & UART communication routines, try as we might I would not work, I had pushed the same FPGA to 250MHZ for another project, so it was unlikely to be clock related.

A new Beginning
It now seems that all these issues have now been solved after designing a completely new Power supply with improved layout (we also added two MASSIVE power planes which also act as a heat sink).

The FPGA design is now consuming 10W-15W per board and we have pushed the core to 370MH/s… yep a single core doing 370Mh/s….

So where is the power going?
0v95 Supply is sitting at about 6-7 Amps!!!
3v3 Supply is consuming about 1 amp, but that can be reduced since we have about 16 diagnostic LED’s strung off the IOAUX power line.
We may need to try and parallel up a couple of the 0v95 supplies in an attempt to cool the switching FETS down, we could just change the Capacitor/Inductor fet configuration, but that can be a real pain to get working efficiently, far easier to just parallel up a couple of supplies.

What is the point with ASICS being released soon?
Well:

  • We just picked up a load of FPGA’s very cheap on Ebay
  • The cost of a single Bitcoin is over $100USD
  • We only need to mine 1.5 coins and the FPGA’s are basically ‘free’
  • Once the FPGA’s can no longer be used to mine Bitcoins, there is Litecoin.
  • Litecoin?
    Yep in good old hacker style, we may have discovered a weakness in the Litecoin system that would allow us to mine without consuming massive amounts of ram.
    We say ‘might’ because we have only looked at the system very superficially, but if we are correct then with a minor performance hit we could limit down the ram size.