Cairnsmore1 - Quad XC6SLX150 Board

[rjk]

please use molex connector.

the pcie connector is very limited per psu.

What?
The "molex" connector (i.e. peripheral device connector) is only good for about 35 watts, if I remember correctly. The PCIe 6-pin connector is good for 150 watts, however.

I guess he meant the number of PCIe6 connectors per PSU is limited, i.e. a somewhat standard one has maybe 1-2*PCIe6 but 8*Peripheral. You'd need to split the PCIe to power up to 4 Quads.

OK I get it, but even then there are more peripheral connectors than you will actually be able to use. Often, there are 3 to 5 4-pin connectors per cable, but the whole cable can only support about 50 watts. So you wouldn't be able to use them all without melting something.

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[seriouscoin]

another suggestion to yohan is .... why not modular design? each LX150 is on a small miniboard that can be replaced. This way if one chip has gone bad, we wouldnt be left with a handicap 3 FPGAs board

Beside, this might give us option to "upgrade". I dont know FPGA much to see if thats possible.

[yohan]

Update on our warranty policy. It has been extended to 1 year for our Cairnsmore1. We will review that further once we know a bit more about the board.

Yohan

[simon66]

Update on our warranty policy. It has been extended to 1 year for our Cairnsmore1. We will review that further once we know a bit more about the board.

Yohan

You should update the first page with a pic and put the prices to stand out. (maybe change its colours or make it bold or something.)

[MrTeal]

Unless I'm missing something, I don't see a reason why having one FPGA go out would take out the whole board anyway. Having daughterboards seems like an added expense for not a whole lot of benefit.

[yohan]

We actually thought about the possibilities of a failure and that is why each FPGA has it's own 12A core voltage switching regulator. We have actually made it possible to shut these down independently for power saving when not in use. We can use that as a last resort in a major problem event. It also a lot better situation if a fault is detected at 12A rather than a combo 48A supply. If you don't "see" a fault until you hit 48A and that might be a burning board by then.

The controller runs off the USB feed and it can be operational for debug or any other useful purpose without powering the main array. This also lets us phase power up reducing big surges at switch on.

We have thought about modular systems and I can understand how some people sell them as a good idea and we might do one eventually. Depends what level you want to be modular at. The negative side of this is that it is more expensive to manufacture say a motherboard and 4 modules that's because you but 2 types of PCB, 5 actual PCBs, and the assembly cost and test costs are close to 5X that of a single board approach. You also add the cost of connector and the electrical losses in currents passing through them, Connectors also add another thing to fail and more thimgs to buy and assemble.

Thermal design of a modular system can be poorer as well if not done well that can increase the fail rate of boards as a result.

[rjk]

Can you estimate the efficiency of the power subsystem? How would the efficiency compare between 4 small regulators vs. 1 large one?

[yohan]

The efficiency is much the same between the 2 approaches. But having 48A, say around a big regulator, in a localised area causes losses in the copper of the PCB and causes heat. In the structure we have 12V at say 4-5 amps max is the distribution and this is a relatively low loss. Similarly the max point at the output of the smaller regulator approach only has to deal with a max of 12A so less loss and heat. This is a simplistic analysis but reasonably accurate.

Distribution voltage also effects the efficiency of most regulator circuits. 12V going down to 1.2V tens to be less efficient than 5V going down to 1.2V. However this is offset by the higher distribution loss of 5V. So it's swings and roundabouts which way you go.

Efficiency of most regulators varies with output current. At low currents they are usually poor. At high currents they lose some efficiency. That's copper conduction losses mainly. The best place to operate tends to mid capacity e.g. about 6A in out 12A circuit case. In this there is an equation where operating your FPGA at maximum might not be the best return and you might be cheaper with more FPGAs doing the task. Remember FPGAs have metal leadframes and solder balls which also have a conduction loss.

[rjk]

Efficiency of most regulators varies with output current. At low currents they are usually poor. At high currents they lose some efficiency. That's copper conduction losses mainly. The best place to operate tends to mid capacity e.g. about 6A in out 12A circuit case.

I guess that's why many power supplies have their peak efficiency at 50% load? So you will be having oversized regulators then?

I like how you can completely disable an individual device at the power regulator level without affecting the others. This is something I don't think I have seen on other boards, although it could be the case on BFL's Single. They have what appear to be 2 banks of 8 MOSFETs (One per FPGA).

Will the controller device that interfaces with USB also have the capabilities of running its own operating system? I guess there aren't plans for Ethernet on this board, but that might be something to consider in the future if others want it.

[yohan]

We will look at something more complex with Ethernet and a few other ideas but we won't do much on this for few weeks or a couple of months. We have lots of non-Bitcoin projects to keep on target as well.

In the short term we are going the other way and going to offer Cairnsmore with 1 or 2 FPGAs only as lower cost entry level system options. It's not quite modular but an option some people might like. I add some info on these in the next couple of days.

[Keninishna]

please use molex connector.

the pcie connector is very limited per psu.

What?
The "molex" connector (i.e. peripheral device connector) is only good for about 35 watts, if I remember correctly. The PCIe 6-pin connector is good for 150 watts, however.

I guess he meant the number of PCIe6 connectors per PSU is limited, i.e. a somewhat standard one has maybe 1-2*PCIe6 but 8*Peripheral. You'd need to split the PCIe to power up to 4 Quads.

OK I get it, but even then there are more peripheral connectors than you will actually be able to use. Often, there are 3 to 5 4-pin connectors per cable, but the whole cable can only support about 50 watts. So you wouldn't be able to use them all without melting something.

I'm pretty sure it has molex and a pcie connector it will use either one for power.

[yohan]

There 3 ways of puting 12V into this board. The first is a jack either 2.1mm or 2.5mm (TBD). There is hard disk drive connector (usually refered to as Molex) and there is also a PCIe (6way) graphics power which incidentially is also made by Molex.

It is also possible to use the disk drive connector as an output to power a second board when using the PCIe graphics as an input. I would not recommend more than 1 power chained this way except when they are the dual or single versions of Cairnsmore1.

Depending on who makes a disk drive connector, and the mating half, the contacts are rated between 5A and 10A. On 12V input that gives a range of 60-120W. We also have a possibility to run on a slightly higher voltage (to be confirmed) say 15V and power then scales 75-150W. It's the current that matters on these connectors.

On power supplies it may be worth considering a single rail industrial style power supply for racks. We are going to look at this and it may be a more cost efficient path for arrays of boards.

Yohan

[testconpastas2]

Nice addition  of PCI-E and temp sensors....

I'd pre-ordered one of your boards but after your enhanecements  I would like to get 4 more. are pre-order still open??

Thank you. I think at the end I've found my EU zone "shop".

[yohan]

Pre-order is still open but we may pause it for couple of days sometime this week whilst we take stock on a couple of the more minor components and whilst we see how many we can "grap" either from our other projects or find from the general components market. 

For existing pre-orders there isn't a problem unless we are let down by one of our suppliers. The highest risks at the moment in this respect are the heatsinks and fans which there are other option albeit possibly not so good options compared to those we have selected.

[simon66]

Quick question. Do we have to pay full price at once or what? Also can we start paying already?

thank you.

[Glasswalker]

Quick question. Do we have to pay full price at once or what? Also can we start paying already?

thank you.

I believe yohan has said that you won't be expected to pay for your pre-order until they are either close to ready, or ready to ship. But I assume at that point, payment in full will be required.

Also I don't believe it's possible to pay right now (they are still sorting out possible payment methods and such).

But I'm just speculating based on previous posts in this thread.

[pieppiep]

It's an already existing company with already existing products, so my guess is the methods of payment they already support will be supported but they're examining if paying with bitcoins can be an extra option.

[yohan]

Payment will only asked for when the unit is more or less ready to ship. In reality what we will probably do is look how many boards go through test in any one day and ask the next set of people for the money at that point with the idea of packing those units the day after. The only exception to that will be the bypass that we are going to try and give everyone 1 unit on an early shipment.

As the list of people is getting very long we will probably have to freeze the list for the early ship offer very soon.

As said we are looking at Bitcoins but initially we will use our traditional payment methods which are bank transfer, PayPal, credit or debit cards.

Yohan

[area]

How do we express interest in a preorder?

[yohan]

To pre order send an email to bitcoin AT enterpoint DOT co DOT uk with address and contact details.

Yohan