Topic: GekkoScience BM1384 Project Development Discussion - page 89. (Read 146665 times)

Okay, so, the BM1384 appears to really like current while initializing. Even with a fairly stable regulator, the starting problem for higher frequencies didn't go away. I once had it running at 175MHz, but I think I had the input voltage to the buck cranked up. Nothing I did within reason to the circuit could get it to handle the brief burst current required to start the chip above 150MHz. This included adding 22uF bypass capacitors to all four corners of the chip, increasing output capacitance of the regulator to 8x 47uF ceramics, and building a socket onto the regulator board so it'd plug straight into the breakout board and get rid of wiring impedance.

To make sure it wasn't the chip's fault, or the breakout board's fault or whatever, I rigged up a stupidly-overcapable regulator by cutting a chunk off a dead AMV1 Garden blade courtesy of CrazyGuy. The 53355DQP on there is rated for 30A, I figure that should be good enough. I modified the board to socket straight to the breakout, powered through a USB jack, and with a voltage range adjustment of 600-750mV and tested the chip successfully up to 250MHz (13.75GH) with that attached. The current meter on my bench PSU touched 1.8A during the chip-init burst transient, but the running current was around 1A.

So what I'm thinking is, screw that IR3899 anyways it doesn't seem to be able to handle that burst transient. If it's pushing 9W of 5V at 85% efficient down to about 630mV that's briefly touching an output current of 12A. I knew output current was the cause of my undervolt issues, but the outputs I was seeing didn't make sense for overcurrent protection when compared to the datasheet info. Given that I ruled out literally every other fault condition though, that has to be it. I'm not sure why the chip was reacting in 2.4mS instead of the 20mS listed in the datasheet, but whatever. So yeah, screw that chip anyways.

I think we're gonna go with what we're calling a "Baby Chuckwagon" strategy, which is instead of trying to jack with some unnecessarily-complex freakin' tiny-pin-pitch (or more likely, cut-up no-lead) package chip, we're gonna work out a design using a basic regulator controller with integrated FET drivers, and a couple pretty good super-low-Rdson external FETs. It'll require more board space, but the parts cost should actually be a bit cheaper, and the packages are decidedly non-evil.

While we're waiting for those parts to come in for testing, I can crank up the voltage on the schfifty-three board and start testing chip strings to prep for Amita design. How sweet would it be if I posted something tomorrow about how I had a two-chip string pushing 20GH or whatever?

I just mailed 2 to novak and sidehack.

I think I have a few NF2s left around - they're considered "defective" as the asics underperformed significantly (and I haven't bother to unsolder them). Aside from that they work sufficiently fine for testing and experiments. If you want PM me your address and I can mail you one.

Ahhh.... it's been a while since I've seen my creations
And by the way if you have any questions on them or if I could be of any help with reusing parts of that design - let me know.

I already know that the voltage regulator will not be a good fit - it's lower limit is 0.8V (although the dual-chip version used a 6A one which might still be usable). Ripples were quite significant too - 30mV (but that might also be within the tolerable limits). It was a very cheap option though (and which is why I used it)

And software is the other major issue - currently the design is stuck with this USB-Serial chip as this is what cgminer supports and that's the only documentation on the BM1384 (yeah! seriously!). The specific USB-serial chip is not really bad but an alternative one could easily save another buck or so from the final price. I guess for the moment that's a reasonable compromise - spend a bit more on components and a lot less on software development.

Oh - and almost forgot - note that black heatsink! We paid a bit extra for them but they were well worth the money and in terms of performance they exceeded the competition by a large margin! Really good ones! The downside is that they were 40x40mm so the board was redesigned around them and that's why it is a bit bigger.


And kudos to novak and sideshack! Great job!

So I slapped the regulator around some more today. I was really hoping that compensation issue would be the end of it, but nope. Not the case at all. I built a powered USB port and put a jack on the regulator test board to simulate the input conditions it'd see from a powered hub, and fitted a socket to the output so it can mount directly on the breakout board to minimize output wiring effects. Rehashed the compensation with higher input and output capacitors to help buffer load transients. I beefed up capacitor bypass on the VCC lines and tied them to power through a 4.7ohm resistor to help keep out burst current discharges on the bulk caps from affecting their voltages. The Enable line looks like it never gets below about 2.4V, twice the threshold for turnoff. Pretty much the only thing left is to isolate the soft-start pin and see if it's getting jerked low and causing an output discharge. Hopefully I can get it worked out tomorrow.

Also, I did the math and if I just stick a linear regulator on it set for 0.6V, the chip should still reach about 1GH off a 2.5W USB port which means that, at the absolute worst case, it's still three times the efficiency of a Block Erupter.

Ok, I see where you're going on this.  Yeah, if you want to look into that sort of thing that would be pretty cool.

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novak

pm me an address:

  I will mail a dead dual chip and a good dual chip NF2 to you.

Well efficient is not the point. Education requires something that works. Is budget friendly and something that can be used by a group huddled around a laptop also note shipping costs will be a lot lower for a more worldwide distribution. Power Supplies, loud fans etc not really conducive to learning environments. Stickminers are perfect. Ok no worries as this would be ideally something we can discuss if you have some free time and workable units. I will keep checking back in with you guys when you are nearly there. In the mean time I will map out some lesson plans etc for our students on this potential project so if and when things are right on your end we are ready to go here.

@phil
We do not have any of those dual chip (NF2) miners, although we do have a couple of the similar six-chip NF6.

@bick
That is an idea but that's going to be a ways out as right now we don't even have miners.  At such a point as we did have miners, pretty much anyone would be able to do something like that by purchasing miners.  Or you could purchase existing miners now.  That would be more efficient than stickminers in the ~$500 range anyhow.

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novak

my bad

front and back of 1 chip ice fury and 2 chip bitfury

Please elaborate on which part of that multi-person rambling you're responding to, as well as the idea itself.

@ Novak:

Maybe something that could be built upon and given to schools for working on Bitcoin projects. Might be worth looking into as education based project worldwide to spread Bitcoin to schools. A Bitcoin for Schools Stickminer Kit would be something to promote.

You certainly could have our school willing to help promote this as stickminers kit since they are much easier to store and handle compared to the FPGA X6500 Rev 3's we were using in the past. Our kids mined Freicoin with the FPGA's for a few weeks off and on 2 years ago. They also all have cold wallets in Freicoin but are interested in Bitcoin as well.

---

You know we could have access to the 1100 Hammer Spondoolies chips if I can find / get funding and I might have a number of people interested in doing that with the Freicoin Alliance as they have funded a school project we had last year building a bake shop at school.


Project Idea


1. Students build a small package or kit including a stickminer you design / build for schools and sell them. (Kit have directions / lessons for teachers and students / manual etc.)
2. Students will seek loan funding from members of the Freicoin Alliance with potential matching funds from Freicoin Foundation via a formal proposal to purchase the chips / and parts and possibly.
3. Your team decides if it is viable what you are willing to contribute and what if any compensation you would require. (Depending on your needs / time etc)
4. Students sell kits and pay back loan to those from the Freicoin Alliance.

Very rough thoughts.

https://freicoinalliance.com/topic/49-active-loan-204000-frc-november-2014-may-2015/ Completed Loan Bakery Project.


Edited per sidehack request:

Also, looks like I might have found the issue with regulator stability. There was an error in my crossover frequency calculation (partly due to a really poor explanation of some things in the data sheet) which put me off by a factor of 6.5, shifting what I thought was a reasonable frequency to base calculations off of about an order of magnitude high. I'm hoping that explains the poort transient response I was seeing, as well as the high-load instability. I've recalculated everything (this'll be regulator iteration six I think) based on the feedback values I calculated earlier today for the 600-750mV adjustment range and the altered crossover frequency calculation (which affects the calculations for five of the six compensation components).

I'll scrounge up the closest parts I can find (most calculated out to pretty straightforward values) in the morning and see if I can't get that regulator stable. I'm really looking forward to reduced output ripple and high-current stability. I should be able to push this thing enough to ask for about 1.6A off the USB port. If it works how I expect it to work now that I'm pretty sure I know why the last five iterations didn't work (since I've been using the flawed initial formula from the beginning), we should be ordering test Compac PCBs later this week and I'll be able to run out a set of hashing efficiency curves for the thing using the prototype boards. Hopefully I can talk Novak into integrating the arbitrary frequency code into a cgminer driver in the next day or two so I can run curves with a lot tighter data points than every 25MHz. I guess I could just crack open the source code, add to the lookup table and recompile, but software is his job anyways.

Also, if you haven't seen TheRealSteve's Block Erupter Hack-off go check it out. We're already scheming on a couple ideas.

Phil - we should have some IceFuries inbound. I can't tell from an end photo what is what in that picture so I can't answer any more than that.

Meech - maybe, if it weren't a completely different protocol and also garbage controller software that'd be impossible to work with. We'd end up having to build a new backplane to fit in the case, as well as new boards, and it'd end up being us purpose-building a lot of new and fairly complex stuff in order to use the box it came in. Not really the best thing to put effort into, so no.

If anyone else asks about whatever else hardware we could look at building for, I'm going to direct them to this post:

NO.

I've already got enough on my plate with the FOUR miners I'm already designing solo and from scratch, and I'm not going to add a fifth, or sixth, or seventh thing to a list that's already probably longer than we can feasibly pull off with the resources currently available. Please don't ask again.

Could you do anything with the Block Erupter Cube?  The case would make for a perfect upgraded lil miner.  Have one for ya if you want.

speaking of your museum do you have

A)none of  
B)either of
C)both of these sticks?

 If you need the 1 chip ice fury or the 2 chip fury stick in the photo let me know via pm

looks like you're doing custom sink, yes? i was going to, but probably way to late now, use northbridge/chipset heatsink mount points? you could by them fake copper aluminium sinks for a dollar a dozen off ebay, they work well enough to dissipate 15W of thermal passively

No, probably not. As I've mentioned a couple times so far in this thread, it's not likely we'll build S2 upgrade boards since the hardware design is basically a one-man team, the funding for the whole dev side of things is fairly low, and that'd be a FIFTH thing for me to work on. If Bitmain bails on the design that they already have completed and are apparently testing, maybe we'll give it a go but I probably won't have time until late enough in the year that the BM1384 has already been replaced.

Like those that can act as a replacement of existing S2 blades?..   

It looks already that Bitmain will never release such a boards........

Thanks, hacko86, I'm glad people are getting excited about this.  I'm excited about it.

As has been stated a few times:  We're looking at building bigger boards, specifically one half the size of an S1 blade and one the size of a prisma board, to refit onto existing heatsinks.  The prisma board should be about right for those who want to build a rackmount miner as well, as it should go nicely in a 4U case.


The stickminers are stickminers.  There's a good reason not to try to build a whole farm out of them:  You have a power regulator and heat sink for each chip.  That makes the price per GH pretty bad- just look at any other stickminer.  However, it is still a fun project as a stickminer- and most of the design for a stickminer (besides just the PCB layout) was already done as we were working up our breakout board for the chips.  

However, anyone that hacks stickminers into another form factor still gets mad props.  One of the coolest things about stickminers is that they are a great learning tool, especially if you don't have hundreds of dollars to spend.  Ours should continue the trend of being fun to experiment with as it will come with built-in voltage adjust via a potentiometer.

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novak