So this first post will be somewhat incomplete. I have as of yet no diagrams drawn up except sketches on paper. Dimensions are currently in inches, but a fairly universal standard should probably be defined in metric since the majority of manufacturers and customers would be more familiar with that system.

But here's the score so far. I am interested in building miners that don't suck. To that point, I am interested in building miners with reusable parts, with standard interfaces and with full adjustability of chip-level operating points inherent to the design.

My intention to build a board which can fit on an AntMiner S1 chassis has already been discussed at length. I have no problem using that base hardware as a fairly standard small-format miner. I don't know of any terribly good large-format (say, rack-mountable) miners which are generic enough to do what I'd like. So Novak and I have discussed and would like to propose for comments a basic standard for rack-mountable bitcoin miner, which is designed to be inherently flexible and upgradeable.

I should have some layout diagrams generated in the next few days, but for now I'll give a bit of a text description.

The case

4U Rack-mountable, 7 inches high by 17.5 inches wide outside dimensions.
A total of six 38mm 4-wire PWM fans, three 140mm at the front and three 120mm at the back in push-pull configuration.
Two server-grade power supplies, 1U height, probably DPS-1200 or functional equivalent, mounted at the top rear on an internal shelf separating the hashboard volume from the upper chamber containing controls and cabling.

The hashboards

The span between front and rear fans (inside to inside) is 15 inches.
The hashboard PCB is five inches tall by twelve inches in length and bearing two heatsinks.
The main heatsink is four inches tall by ten inches in length with a total fin height of no more than 1.38 inches.
The secondary heatsink is four inches tall by ten inches in length with a total fin height of no more than 0.5 inches.
The secondary heatsink would be drilled for screws to run through, through the PCB and thread into the main heatsink. This is so that the secondary heatsink can, if the PCB design calls for it, be removed without hindering the mounting of the PCB to the main heatsink.
The main heatsink would be drilled and tapped through the fins such that it can be screwed to the bottom panel of the case.

The heatsinks will be aligned with the rear bottom corner of the hashboard, such that the topmost one inch and frontmost two inches of the hashboard have no heatsink contact on either side. This gives room for through-hole components, VRMs, connectors and other circuit parts.

There is a one-inch gap between the front of the hashboard and the inside of the front fan. There is a two-inch gap between the rear of the hashboard and the inside of the rear fan. Hashboards would be mounted perpendicular to the bottom of the case, with heatsink fins extending horizontally outward from the board.

Each board should have two 6-pin PCI connectors extending at a right angle from the top of the board, just past the end of the heatsink (the rearmost edge of the rearmost jack would be 10" from the rear of the board). To the front of the frontmost jack is the USB header. All connections would be accessible from holes punched in the separator shelf.

8 boards will fit widthwise across the inside of the case with a bit of room inbetween to ease vertical installation.

Boards should be limited to 300W maximum power dissipation each.

Controls

It's our intention that the controller can be fairly generic. Any small single-board-computer like the Raspberry Pi, Cubie or BeagleBoneBlack would be suitable provided it had both USB and Ethernet connections accessible, and one could compile cgminer for said device.
A space inside the upper chamber would be reserved for a "drawer" onto which the controller is mounted; dimensions for this are to be determined and a replacement controller should be provided with its own "drawer" tapped in the proper places for mounting said controller.

A board specific to the miner is to be assembled providing a modified USB interconnectivity on 8 ports. The connection would be a six-pin header, onto which would be socketed a cable with five wires and a shield. Four of the wires carry standard USB lines (5VDC, GND, D+, D-); the fifth wire carries a logic-level signal for a status LED. The sixth pin connects to the cable's shielding. An identical six-pin header would be present on the hashboard, which enumerates as a USB device and controls the status LED. The status LEDs would be visible through the front panel of the miner.
This board connects to the controller, which sees it as an 8-port USB hub.

The board would connect to thermocouples mounted in the airstream in front of the rearmost fans. All six fans would connect to this board, which would use the thermocouple feedback (and a calibration trimpot) to determine fan speeds, individually for each pair of fans.
Alternatively, if software control was desired, the controller could link on an unused USB line and interface with a cgminer driver tasked with determining fan speed from hashboard reports and pass commands to the controller on the board.



The goal of this endeavor is to define a standard box inside which any board designed for its form-factor could be run. By using a standardized dimension, heatsink and USB interconnect, boards from different manufacturers with different chips operating on different protocols could all be run in the same box off the same controller. Operating new boards might require updating cgminer on the controller to detect the new hardware. Piecewise upgrades would be readily possible as hashboards could be sold individually. As long as the basic dimensional standards are met, as well as the basic operating standards (12V 300W max, USB connection) and avoiding software conflicts, any number of small or large manufacturers could produce any number of boards which could all be run together in the one box. Replacement parts for the machine itself would be both standardized and fairly generic. The benefits in cost savings, maintainability and diversifying the market are substantial.
I know it's not a perfect household miner being as it would look to draw over 2.4KW power. The point is not to build a perfect household miner.


So, that's the gist of our idea. Anyone got any comments?

I will not use USB3.0 for the data bus because there are no good options for USB3.0 to microcontrollers or primitive protocols which hashing chips are likely to use. USB2.0 should have more than enough bandwidth for everything.

There would be no box with 12 boards on the controller. At most 8. One controller per box, ethernet out. The USB interconnect is strictly internal, tying the controller to the hashing boards.

okay sounds good so far. i would like more inter changeability of hashing boards no point re-buying the wheel each time.

10 inches long contiguous aluminum heathsink?

The thermal expansion of such a slab of aluminum will be literally ripping the chips off of the PCB.

Either the heathsink or the PCB needs to be partitioned into sectors.

Have you ever looked under the GPU's heathsink? How many chips it touches and where are the chips in relation to the heathsink?

I guess after re-reading the original post I missed the fact that the hashing chips may be in the supply-voltage-serial a.k.a. string configuration. Since each chip will have different ground potential then there is some sort of galvanic isolation provided between the chips and the heathsinks.

So the heathsinks may be able to slide over their isolation layer enough to accommodate thermal expansion.

We checked several other miners for heatsink size comparisons. The S1/3/5 heatsink is 9 inches long; the Avalon2 box and S2 have about ten inch heatsinks. I think the Dragon was more like 8 inches. None of them do quite 300W per heatsinks at stock power either though.

The heatsinks should not be adhered to any chips, unless your thermal paste hardens up I guess. I've never really liked not having some kind of isolation between heatsinks and any electricals. A top-cooler like the BM1384 wouldn't need isolation of its own, but if you had the backside (with its multiple ground planes) on the sink you'd definitely want an electrically insulating thermal pad.

The boards wouldn't have to be string. The 1" at the top can be used for logic level shifters in a string design (or if you drop the small heatsink you have the entire backside for a double-sided board like the S5) or it could be used for VRMs. We don't want the board dimensions to limit your topology choices.

Course, there's also no particular reason the heatsink has to be a single slab. It could be two five-inch chunks maybe with a slight gap between to allow for expansion. It's exactly for considerations like that that we wanted to open discussion - if it's going to be any kind of standard, it needs to be as good as it possibly can be.

I'd like to see the big guys adopt a particular standard, or at least utilize it. Being able to build boards for an existing case without having to build the case also opens up potential for independent manufacturers to get in the game. I mean if you want a computer you can call up Dell or HP or whatever and get a complete system, or you can dig out an ATX case and go fetch guts from NewEgg that all fit inside. You got choices. Some little two-man outfit like mine can build boards but doesn't have the tools to manufacture cases? So what? They can still put out a decent product because you can get a case from someone else - or maybe you already have one. Updating cgminer would be the only really tricky part. If something like PlanetCrypto's independent chip dev happens, or the main guys get back to selling chips to third-party manufacturers like some of 'em used to do pretty regularly, we can have mom-and-pops coming up with innovations and servicing the small-time miners again and doing some pretty good stuff.

2112 - have you talked to PlanetCrypto about chip dev at all? I figured something like what he's doing might interest you.

Testing boards doesn't have to be that tricky. Instead of screwing it onto a greased-up S1 chassis, plugging it in and then taking it all apart again, just rig up a clamp system on a free-standing cooler. Drop a board in, maybe have some pegs to keep alignment on screw holes, light pressure clamp presses it to the heatsink and you plug it up and go. Release the clamp, pull the board and put it in a bag.

If you use good fans, push-pull configuration is a waste. The only effect it really has on a rack-mount case is to reduce back pressure, VERY little effect on actual flow.

 Based on measuring all of my existing rack mount cases, I'm not sure if you CAN fit 3x140mm - be nice if you can, but 3x120 is good if you can't.
 ALL of the 4u cases I own have appx. 16.5" of space between the handles (I have one 2U case model with about 17" thoiugh). Height isn't an issue.
 Might need a custom case design, or at worse have to use a specific case model that doesn't have handles.


 IMO don't use USB. USB connections to miners have ALWAYS been an unreliable PITA. Tolerable for small stuff on the block erupter scale as those are more "toys" than real miners anyway, NOT tolerable for a full-up rack mount large miner. PCI-E 1x or just PCI would be tons better from a RELIABILITY standpoint.


 Would be nice if an industry standard existed, but I doubt a custom design would be practical from a cost standpoint and I don't see the MANUFACTURERS ever getting together to create or work with a standard. 8-(

1)  Or have it open across the back to let the air out.

2) No, the PSUs go over the top of the fans, not beside them.  Hence the 4U.

4) Not really any reason to use thermocouples over any other board mounted temp sensor with a cable alongside the USB.  I agree that a totally separate thermocouple is probably asking for trouble.  It's not correct to assume that you would know the input and output air temperature as the number of boards and the type of boards is explicitly undefined.

6) No more than 8 PCBs would fit given the heat sinks, but that many would not be required.

--
novak

Dogie, regarding your various points:

1) You want negative pressure displacement, likely you'll get better performance dropping the fronts to 3x120's or 2x140s and leaving a grill. Ramming in more air than is being released = high pressure internally = lowers airflow significantly.

With 3x140mm the entire front face is pretty well covered by fans. Looking at bladed miners like the S2, you can tell exactly which boards are between fans by looking at the per-board temps. I'd like to avoid poor-coverage zones like that if possible.
The rear fans were dropped to 120mm because of height requirements for fitting in PSUs. If that ends up actually restricting the airflow, we remove them and put in a grill instead. I'm not a fan expert and these points need to be evaluated by someone who is.



2. 3x120mm = 360mm
Spacing = 15mm
PSUs    = 2x44mm = 88mm "mounted at the top rear on an internal shelf"
Material thickness = 2x2mm = 4mm
= 467mm
Your specified back side is 438mm

The hashboard volume occupies the lower 3U (approximately) of the 4U case. The top 1U is separated from them with an internal panel above the hashboards (which mostly seals them off and keeps main cooling airflow restricted to between the heatsinks and boards) and is where the PSUs, controller and all cabling live.

3) 1U = 40mm fan = annoying as hell. (See SP10 and SP3X where the PSU fan was far louder than the actual miner)

Yes, 1U fans are really annoying. If I'm thinking right, the DPS1200 fan is quieter than the thing on the SP supplies but it's been a while since I fired one up. I prefer server supplies pretty much universally to ATX and would consider installing an ATX supply to be a waste of space, a waste of cost, and really asking for failure.


4) Thermocouples are a shipping hazard as they can come loose and end up in fans and so addd another layer of inspection. They take too long to install and they're also superfluous as you should have already characterised the relationship between ambient intake and chip temps.

Yeah, temp control hadn't been thoroughly discussed hence why I made brief suggestions for both hardware and software control. This point needs to be ironed out.
Regarding characterising ambient intake versus chip temps, how do you suggest we measure ambient intake if not by the same means as measuring exhaust? Additionally, as Novak pointed out, since the board design is deliberately unspecified there is no specific requirement (at present) for this to be true.


5) Remember that the distance you actually care about is between the outer two mounting holes, not the length of the entire heatsink. The material on the ends doesn't contribute to thermal expansion mounting stress.

There are no screw patterns specified yet, but it seems likely that the outer two mounting holes will be very close to the edges of the heatsink.
I'm no expert in thermal management so the heatsink point should be evaluated by an engineer knowledgeable in that field, make sure we can safely dissipate the heat spec in the volume provided with the expected mass flow of air.

6) You've not explicitly specified how many PCBs.

"8 boards will fit widthwise across the inside of the case with a bit of room inbetween"
The maximum number of boards you could fit is 8. The minimum is one. The machine must work properly with any number of boards between 1 and 8 inclusive.


7) 4U should be smaller than 7" if you want stuff to actually fit, even if its shaving off a few mm.

The hashboards are specified as 5" tall, which is about 6mm shorter than 3U. If the upper room (cable tray, whatever you want to call it) is at most 1U high, we should come in under this. If that's not good enough (which can be determined without a lot of trouble), I'd probably convert inch-measure specs to metric with a fixed 1" = 25mm conversion which gives another 2mm height reduction to the boards. If that's still not good enough I reckon we'll have to do some tweaking.



Regarding horizontal width - have you measured many rackable miners for width, or just servers? Most miners I've seen aren't too concerned with rails, which eats about half an inch off each side.
A custom case design is exactly what we'd need anyway, I think, so we should be able to specify our dimensions any way we want that doesn't violate rack requirements of maximum height and width.

Using PCI or PCIe requires using a backplane board with sockets. That can be a significant expense. It can also be significantly more fragile and cause board-mounting reliability concerns. It also, within this design, would require a lot more disassembly to disconnect one board. How many bladed miners have used an internal cable connection to the blade instead of a backplane connector, and how many of those cable connections have been unreliable?
We're not intending to use USB jacks (and especially not garbage like USB micro) which can be pretty flakey. The spec we propose is a pin header, which a decent pin header with a decent cable can sit there for years without losing connection.
Since USB hardware isn't used, the only real USB in the spec is the protocol. I assume not many off-the-shelf SBC (or whatever little guys like the Pi are considered) have PCIe built in, which means even if we want to use PCIe hardware for connection (which I don't, from a mechanical reliability and cost standpoint) we can't use PCIe protocol without moving to either a custom-designed or significantly more expensive controller. If, then, we want to use PCIe hardware we need to use a different protocol. Something everything supports. Something that is easy to adapt into the chip-level protocol. Like USB. I propose that USB protocol is common enough and flexible enough to do the job well, but that using USB hardware connections internally is a bad idea so something more resilient (and also cheaper, and also allowing for more mechanical reliability in the overall design) is suggested.

Dogie over in a Bitmain thread summed up my opinions of a PCI backplane pretty well in response to an S2 question: "It required a motherboard, slots that often broke, large areas of dead space for cooling and is probably the only Bitmain miner that was susceptible to shipping issues."