Topic: GekkoScience BM1384 Project Development Discussion - page 88. (Read 146665 times)

He probably didn't mean yours specifically, but a general "you". A lot of folks have cheap 7-port powered hubs which would be okay for stock settings but nowhere near what these sticks should be capable of.

Did I say I had a 2 amp low quality hub?  But thanks for the example.

The most steady current I saw was about 1.4A, but mind you that's for two chips on a regulator which should be 5-10% less efficient than I expect for the final.

It is with a high quality hub, and a robust power supply behind it. Your generic 7-port hub with a 2A power supply likely won't cut it, and certainly not for 7 ports!

Is that reading @ 16-22gh still @ 1.2 - 2.1 amps or still do-able from a usb hub?

Looked at the hash rate over nite you had a dip and then a recovery.  which is better then a dip and a flat line.  keep working at it. looking forward to playing with them.

Thanks. Yeah I need to track down the source of the hardware errors in parallel before working on stringing two boards, but hopefully I have something stable before the new regulator parts come in. If that's the case, and the test board regulator works as well as it should, we could be ordering Compac prototype boards (and possibly Amita boards) end of next week.

I enjoy reading this thread and seeing the progress.  I might have even learned a thing or two.  Great work!

Amazing

Can't wait to see it finished...

So, update. I designed two fresh regulators, each using sturdy external FETs. One is using a driver chip with a convenient package but a lowerbound of 0.62V; the other has a sorta sucky package but it also has internal compensation and an adjustable reference down to 0.5V so I have it calculated for an adjustable range of 0.55 to 0.80V which should give people plenty of room to play.

We have parts coming to prototype these regulators, and I'll start with the wider-range one because I'd rather have that lowerbound available. I probably won't be able to play with them until Monday.

I set up two boards in parallel since I have them running below a 30A regulator right now. There's plenty of current headroom. I'm seeing fairly frequent hardware errors, which could be due to heat or crappy inter-board wiring. It's currently sitting at 150MHz, which should be 16.5GH but I'm seeing about 14.5 probably because of errors. I'm going to play with chip addressing a bit and see if it even cares what order chips are in; so far I don't think it does.

Tomorrow I'll tweak things a bit and see if I can't get them running well in parallel at 175MHz (19.25GH or 200MHz (22GH) before I start messing with putting them in a string. Hopefully by cheeseburger time tomorrow I'll have two boards strung, which should shift the regulator efficiency up 5-10%. Very excited about that.

Today's Porn:

The two green boards are the BM1384 breakout boards. The unwieldy length of multicolored cabling between them is the fairly jankety inter-board comms. I stole one of Novak's USB adapters, which is currently running off my powered metered USB port. The dark board off the right-side breakout is a corner off a dead Garden blade, rehashed slightly as an adjustable-output 30A converter that's drawing power through a USB jack plugged into a dummy socket off my bench power supply. The fan is swiped from a retired AM Cube, just in case. I'm pretty sure it's the wiring causing issues though, probably a pretty noisy environment to be running 1.8V 115200baud UART lines through without shielding.

The crappy getup will be mining at Eligius on the burger donation address (1BURGERAXHH6Yi6LRybRJK7ybEm5m5HwTr) in case anyone wants to see how it behaves overnight. If I have time to get a series string of chips going tomorrow, we'll have the first taste of the Amita, and I'm pretty stoked about that.

Oh hey yeah, I sent you an email about some buck chip options and ideas from the last six hours or so of research and calculation. Think about that for a while and I'm gonna fall asleep.

But yeah the test chip, I think it was at 125MHz and it was definitely submitting shares at about 580mV at one point. Awesome.

Me too but I think the chip we're testing on is better than average, or else BM1384s are better than advertised.  We were getting the thing to start at 580mV without a hitch.

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novak

Sure - Just PM me a shipping address!

Yep. I did some quick calculations and it should only take about 220uF to handle the burst transient tolerably before the regulator can kick in. We had something like 360uF on the output and it still bottomed pretty good. Has to be overcurrent protection kicking in (at about 11A). The new design I'm working on right now (literally) I can set the overcurrent pretty much wherever I want, so I'm gonna make sure it'll be good for those kinds of burst transients. If we start testing higher voltages and frequencies and find that the burst requirement gets worse, I can just take the overcurrent a bit higher with a change of one part. The FETs will be good for a heck of a lot more current than this thing will ever need. We're aiming to make it capable of maxing out a 1.5A port in steady state, which it should hopefully find around 300MHz (16.5GH). I mean, it'd be pretty great if it could do more than that. Since we can do pretty much whatever the heck we want, I'm gonna give it a full range of 600-800mV so you can clock it up to 400MHz if you can keep it cool enough. Whatever.

Yeah, the schfifty-three we put on there I think has... 3x 68uF output caps? And it behaved admirably even at starting the chip on about 640mV 250MHz. I didn't test the chip higher than that but I probably will tomorrow. It really wants a higher voltage to run at 300MHz stable anyway. I'm kinda surprised it started at 640. Our homemade regulator (well, except for the inductor) will be about as beefy as a schfifty-three circuit (by which I mean the TPS53355DQP) which has been the favorite of miners for a while now - S1, S2, S3, AM Cube, AM Tube, BTCGarden AMV1, New R-Box and a few other things use 'em without any problems. But they're like five bucks per chip. I can build an equivalent non-monolithic circuit for under $2 in silicon, with better power dissipation since it's less dense.

We tried using a pretty large amount of capacitance.  The thing to remember is that we need to build this into a little stickminer that will go in a USB port, so we can't drown it in caps.  Overall we've been fairly dissatisfied with this chip so using a different controller is not a bad plan.  We have another project utilizing a very similar controller so we already have some confidence in the design.

I think we've spend more time dicking around with this ridiculous regulator chip than the rest of the design combined.  It just won't handle the burst current, even at fairly low end starting frequencies.  We slapped another regulator on there and it worked all the way up.

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novak

philipma1957 - is that Nano Fury 2 still working?  Been a while since I have seen one of those in the wild.  Brings back memories.

They're probably prohibitively expensive and I'm not sure that throwing ever larger capacitors at the problem is a good solution but supercaps and ultracaps can store a lot of charge.

The burst was probably around 12A output, for maybe a tenth of a second. It's long enough that I could see it on the mechanical gauge on my old benchtop supply, so not a microsecond pulse or anything. I'm gonna try to hammer a lot of input capacitance onto this thing and help that out. The schfifty-three is running off a USB jack plugged into a port with a 470uF adjacent, powered off my benchtop supply with about a foot of wire, so probably not too dissimilar to expectations from a decent powered hub.

The baby chuckwagon I'll work on design tonight and we'll send off for parts tomorrow. Between tomorrow and Friday I'll probably test two chips running in parallel off a common core voltage since I have a 30A output regulator handy, then crank up the schfifty-three to output in the range of 1.2-1.4V and see about putting two chips in a string. Once parts arrive for the baby chuckwagon I'll assemble one of those and see how well it handles driving a single chip up to, oh I dunno, 300MHz or so.

The FETs I'm looking at should be good for more current than the inductor will handle, and the inductor is good for more current than the chip will ever ask for. We'll probably end up shifting to a 40mm heatsink. If the regulator beats about 88% efficient at around 600mV we should be able to run this thing at 150MHz (8.25GH) on a stock USB port, which means 0.30W/GH device-level. Which is pretty great. And since we're building the regulator to handle balls current, there's no real reason why we shouldn't allow the voltage into a higher range so you can push the thing even farther. If it'll run 300MHz off the stock heatsink (with adequate airflow) you'd be looking at 16.5GH off about 1.5A from the USB port, which is doable with a good hub, and still more efficient than an S5 stock settings.

I take it you mean 'official' NF1s?  Otherwise, there's plenty of clones.  If you have a BitFury chip floating around (and with blades going for pennies on the dollar, you can have dozens for cheap), you could easily make your own using the open source designs

Slightly off-topic for this thread, but perhaps you should make a list (in a thread or on your site) of what gear you have and what gear you're seeking.  I'm only missing a few (excluding clones) off my StickMiners thread, myself - but have few duplicates.

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That would be pretty sweet.  I'm surprised the veritable plethora of caps couldn't deal with the transient current though - just how transient is it?  Not that there's anything wrong with the KISS approach.

I don't think we have any NF1s though- if you have any of those (even under-performing or damaged) we'd gladly send a little BTC.

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novak