Price is still TBD, but we expect the carrier to be under $300 (with a CM1 or CM3) and the blade boards under $70 (w/o CM3). Add in the cost of the CM, but without an SSD yields around $1.4K assuming the CM 3 is still under $40. That's ~$1.4K for forty 1.2Ghz 64-Bit ARM Cortex-A53 cores!
As for direct mounting the compute modules and the SSD, there were a few issues we looked at. The first was that there was insufficient space for routing the 10 sets of USB, control signals and GIGe in a 4-layer PCB. Because we need controlled impedance for the USB and GIGe we would have had to go to an 8-layer PCB. The second issue is that there are no vertical mount SSD standards, neither mSATA or M.2. SATA Disk On Module (DOM) is a very loose standard and there is no mechanical compatibility. Third, the vertical SODIMM connectors are quite pricey (and not in wide supply) at around $5 each, which is about the cost of the blade PCB.
Finally we felt this would give us some flexibility as to what is actual mounted. We could see doing a different blade with a 64-Bit ARM SoC directly on the blade as opposed to a module.
All in all, it felt like the right set of compromises. And hey, isn't that really what engineering is all about!
As for clearance, the distance from the top surface of the CM to the backside of the next blade is 9mm. Tight, but a small 6-8mm top hat will fit. There are no components on the backside of the blade. This allows the typical pi heatsink (like this one we plan to use from pimoroni https://shop.pimoroni.com/products/heatsink
) to fit.
We will be mounting this in the M350 Mini-ITX case (http://www.mini-box.com/M350-universal- ... -enclosure
) with a couple of 40mm x 10mm fans overhead. Add in an external 12V @10A+ supply and it will all be good to go! Just as long as we can get CM3's!
If anyone has any feedback, questions, comments, etc do not hesitate. This is why we made this post.