BCU1525 Air Cooler Mod

Recently I had an extra Rajintek Morpheus II cooler not being used. I was mining Kaspa (Kas) coin and running a BCU1525 from SQRL.

The BCU is a great FPGA running the Xilinx XCVU9P FPGA , the challenge though is the when running at high speeds and long durations it gets hot!!! Real hot.

Prior to My mod I was mining KAS coin at an FPGA clock speed of 600MHz, I was using a TUL extended Cooler with no less that 3 x 120mm fans and 2 x 80mm fans. Even with all those fans and TUL cooler I was on avg. running at a temp of around 86 deg C. much hotter than recommended. I was getting a hashrate with Team red miner on Linux of about 5.1 GH/s.

Tearing Down The BCU

So the first step was to tear down the BCU. I had mine cooled with a TUL extended heatsink front and backside. My idea was to have the Morpheus II cooler  to replace the front plate of the TUL cooler.

BCU Front and Back Plates removed
TUL cooler front and partial image of backplate

The bracket redesign

Once teardown was completed I also removed ram bricks from BCU as they were too high and cooler would not be able to sit snugly on FPGA. My next challenge was the brackets. The original Morpheus Brackets had holes predrilled for GPUs but were completely useless and different offsets than were was needed for BCU1525. I measure originals thickness had to determine the hole sizes and relative edge to distance measurements. To help me I made a test rough cutout in a thick cardboard material. The challenge was the ram slots limited any angles and the morpheus has 12 heat pipes so I had to cut around and leave room for the bracket to try maintain a flat surface. Once I got a cardboard template I could then get a better idea of measurements needed to eventually make an PDF master file I could send out to be custom cut for brackets. The team at https://www.arvindesign.info/ did a great job on the brackets.

Image below left to right. Original Morhpeus II brackets. Middle cardboard template, far right Final brass brackets. I also need a copper shim for mounting the cooler to FPGA face.

Bracket design steps as well as copper shim.

I also needed to TAP some of the brackets so the original Morpheus II screws would thread.

Tap set to allow brackets to accept hex screws.

I now needed to prep the BCU base because there are many board level components that would need heat fins to now allow airflow to cool them from mounted fans on the Morpheus II cooler.

BCU1525 with new mounted cooling pcb heatsinks.

After heat fins were in place it was time to mount the new brackets to the Morpheus mount. The brackets then use male/female hexagonal screws to allow us to screw the FPGA and TUL back plate to the morpheus cooler.

New Brackets installed and ready for final assembly.

In the image above you will see the new brackets as well as hex screws in place. The one tricky part is the top bracket needs one side to be bent up to go over the heat pipes of the cooler. I used a wrench and manually bent the bar about 2 mm curved. I then added a copper shim between FPGA and Cooler plate. Using paste on FPGA face and top of shim. Copper being a great conductor should help transfer heat from FPGA since the Morpheus coolers plate is to flat and will not make contact with FPGA face.

Final assembly and Mining Prep

I then used screws mounting Morpheus cooler, the FPGA card and the TUL back plate via the 4 main mounting holes.

BCU1525 with mounted Morpheus cooler.

Now I am just using 2 main 120mm fans on morpheus cooler front. I have a 120mm fan from the back of rack blowing air through the TUL back plate fins to help keep back cool. I also needed 2 x M2.5 screws to allow me to connect the PCI faceplate so I could mount FPGA to the rack frame.

Well now final results I am able to run the now Morpheus cooler modded BCU1525 with TeamRed miner on linux. Avg. temperature running for about 4 hrs so far I am at 61 deg C I also have been able to increase FPGA frequency to 630MHz clock speed. This has led to a new Kaspa mining hashrate of. 5.6 GH/s. I also feel I have room to increase clock speeds but I need to first figure out a way to measure total voltage so as not to damage the BCU. I also used a relatively average CPU/GPU paste so with some better paste I think I could shave 2 or 3 degrees further.

Its easy to see the 12 heat pipes of the Morpheus cooler are tremendous air cooling solutions. They are a bit expensive amazon, ebay ranging from 85 to 120 USD. The BCU1525 fpga I would say is as great a cooling challenge as many of the upper tiered Nvidia and AMD graphic cards today but the Morpheus cooler handled it well. Some other side note items related to my experience here. The cooler is so good at radiating heat ambiently in confined spaces you may find it warms up quickly. Also the Morpheus cooler once installed is more like a 2.5 to 3 PCI slot width(though Nvidia and AMDs newer offering can be as well). So definitely case or rack space(for multiple FPGAs) needs to be considered but this can save the hassles and worries of water based cooling solutions.