Getting Started / FAQ with the BCU1525

Information Getting Started / FAQ with the BCU1525

Why did the part number change from VCU1525 to BCU1525?

GPUHoarder said:
I want to be transparent that Xilinx has asked us to update the part number for the crypto board to avoid causing issues with their data center customers because our prices are "too good" You're still getting the same (actually better, it has modifications for crypto) board.

Where are the miners for the FPGAs? Where can I download them?

Software called bitstreams have been released and will be continued to be released by Developers. At the moment Digital Cruncher and Whitefire990 have released theirs, with more to come soon.

Can a VCU/BCU hash at x GH/s on ETH?

OhGodAGirl said:
Under no circumstances can a single VCU1525 or BCU1525 achieve anything above 150 MH/s, at best (even with light cache churn).
Regarding the claims of Ethash in the 1.4-1.9 GH/s range, I'm always to say that few things are 'impossible.' If someone 'broke' the algorithm, maybe it could be possible, but so far of all the so-called 'developers' who have contacted me privately with such claims, none seems particularly smart, and it would take a very smart person to break the Ethash algorithm. Time will tell if any claims turn out true, but I am betting against them for sure.” -whitefire990 pls join

What can I expect if I order a water block for my BCU?

Generally speaking, the VCU on water can keep up with a BCU on air. While A BCU on water can surpass a VCU on water. "Can" is the keyword - as in whether or not a faster bitstream is released for those with this additional cooling. Actual performance numbers have not been tested or published (on the BCU).
The water block makes a huge difference on the VCU1525, but a small difference on the BCU1525. I don't have access to the new BCU heat sink, but on the similar XBB1525 board, you would go from about 15.5GH/s (air) to about 16.7GH/s (water) - whitefire990

Should I order a QSFP28 Cable? If so how many?

The QSFP28 links allow for linking cards for the crazier algorithms like x16r, x17. Outside of this, we won't likely see significant usage, and I can't think of anyone other than whitefire990 who really pushed for the inclusion of a day0 release on QSFP-useful algorithms. If he has said that it's not likely to be used until 2019. I'd imagine that'll be the case across all developer releases. If you do plan or purchasing a QSFP28 Cable, you will need one cable per card, and the last one will loop back into the setup.

What kind of case should I use?

If you’re going with passive heatsinks on the BCU it is strongly recommended to build them into a server case with the least amount of space between the cards that fit your hardware. Active cards need a bit more space between the cards but not above and below; you need room to suck air from, and the goal is to avoid air pocketing for both active and passive setups. If you are water cooling your cards, then use an open air frame, as a server case will most likely not have enough space.

How should I build my water cooled rig?

Generally speaking, you should be using about 240mm worth of radiators per FPGA (350w). Do not mix aluminum components with other metals in the same loop. Even ones with a zinc coating can degrade and begin galvanic corrosion in the absence of a powerful inhibitor in the coolant. If you still have questions about water cooling setups, please refer to this guide.

How many watts can my heatsink/water block cool?

Thanks to a new infographic recently posted by @GPUHoarder, we now have decent estimates on the performance of each cooling solution offered in the first batch of BCU 1525s.

Looking at the image below, we can see that the stock BCU heatsink is capable of cooling 280W Using medium static pressure fans when enclosed in a server case with very little space between the cards and fans on each end to push/pull air.

The upgraded passive heatsink has no added cost (so far), but requires more powerful high static pressure fans at the front and back, and need more length inside the case, while still requiring you to maintain little to no space between cards.

For those of you wanting to use a setup with cards more spaced out, the active heatsink will be required to sufficiently cool your card. The active upgrade costs $50 USD and includes an ultra-high static pressure fan.

Lastly, we have the most expensive option which is the water block costing approximately $150 USD. Some advantages include less noise, full board coverage cooling, and bragging rights. However, you will need to spend even more money purchasing compatible pumps, fittings, reservoirs, tubes, radiators, etc.


What motherboard should I use?

As of right now, there are no bitstreams that require the full 16 lanes per FPGA or even more than 1x (What risers do right now). You can use any motherboard that you want, as long as they work with risers. If you want to future-proof your rigs to have support for x16 electrical and physical (directly inserting them into the motherboard) then you need to start looking at more expensive, beefier motherboards that support threadripper CPUs which have 60+4 PCIe lanes, the board would only allow you to run 3 boards at full x16 speeds, or up to 4-5 boards at 8x. I have not seen any boards that would let you fit more than 4 or 5 FPGAs.

What CPU should I use?

I strongly recommend using something better than a Celeron CPU to run more than 1-2 cards as you will probably overwhelm the CPU. A Celeron will work but with more cards, it will bottleneck your miners and you will see a noticeable hash rate decrease. Generally speaking, you should be pairing a maximum of 2 BCUs/VCUs per CPU Core (1 card/thread).

How many watts does my PSU need to have?

You need a PSU that can push out at least 350W per VCU on the 12v rails. A high-quality PSU 1200W (like HP Server) is fine, but most generic 12/1300W only have 90-100A 12v - and can't handle the power on current onrush. The BCU is more forgiving on this than the VCU due to additional bulk capacitance on the 12v. Keep in mind that a 1300w PSU cannot generate 1300w on the 12V rail, 1300w is the power capacity across all voltage rails. Also, make sure that you read the PSU rating and how many watts it is rated for. Some of those server PSUs are "1200W at 240V" but only 900W at 120V (or don't run on 120V at all). Ensure the unit you're grabbing will remain at the power rating you require on the voltage you can supply to it. Also give it a fan that blows into it on the breakout-board side, unless you open it and reverse the fan. They can get much warmer under load.

Can I use any regular riser for my BCU/VCU?

It is highly recommended that you use a 006C Riser and use a direct 6 pin power connector from the power supply to the riser. The inrush current during the FPGA startup is currently way more than 450W instantaneous, then drops to 300-370W continuous. The variable clock bitstream will decrease inrush current.

How should I wire each BCU/VCU? There’s only one 8-pin connector?

As stated above, use a 006C Riser and a direct 6pin from your power supply to power the PCIe of your card, and use a dedicated 8-pin for each card. Do NOT use an 8-pin PSU to 8+8 connector to connect two cards.

Do I need a voltage controller like the DC1613A?

GPUHoarder said:
September 20th, “We believe we will be able to configure the voltage control through the BMC, but that is not yet finalized as we have only within the last week received access”
Update: External controller is no longer needed, the team has access to voltage through software.

Whitefire "While you don't 'need' a DC1613A for a BCU, it still allows you to change some parameters in the regulators if you are interested in extreme overclocking. Use at your own risk though."

Now for some BCU/VCU1525 Images (Click to Enlarge)

BCU1525.png IMG_20181012_175022.jpg image0 (3).jpg 20181008_184344.jpg image0 (2).jpg image.jpg 213123.jpg image0 (1).jpg image0 (1).jpg IMG_20181002_135509.jpg IMG_20181002_135521.jpg IMG_20181012_175307.jpg IMG_20181012_175004 (1).jpg IMG_20181012_175010 (1).jpg IMG_20181012_175045.jpg IMG_20181012_175055 (1).jpg IMG_20181012_175234.jpg

Special thanks to @GPUHoarder @OhGodAGirl @senseless @Soul of Jacobeh and @whitefire990 for their information on discord.

Have anything to add/change/fix? Message me on the forum or discord and I'll add it!
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  1. Update 1

    Added the new infographic from discord posted by @GPUHoarder and elaborated on the options...
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