GekkoScience BM1384 Project Development Discussion

[sidehack]

Bitmain could probably do it if they wanted, but with a fixed-voltage string it comes down to balancing high hashrate versus chip density. When I first ran the numbers for a potential S2 upgrade kit I was eyeballing something like 3.5TH off 1KW with 100W blades, but their prototype was more like 2.4TH off 6 blades at about 700W probably because you could do it with a lot fewer chips. To get low power means clocking the chips at their bottom end, and to get high hashrate at bottom clock means a jillion chips.

[1713629522]

1713629522

[1713629522]

1713629522

[alh]

I wonder if perhaps since the S5 was originally introduced, the balance of more slower clocked chips has shifted. By now, you would expect that the yields on BM1384 parts is pretty good. That usually drives down the cost of the chips. At the outset though, perhaps the chip costs were expected to be higher so it made more sense to have fewer, faster clocked parts. Of course their view of costs and margins are probably wildly different than sidehack's.

[philipma1957]

I wonder if perhaps since the S5 was originally introduced, the balance of more slower clocked chips has shifted. By now, you would expect that the yields on BM1384 parts is pretty good. That usually drives down the cost of the chips. At the outset though, perhaps the chip costs were expected to be higher so it made more sense to have fewer, faster clocked parts. Of course their view of costs and margins are probably wildly different than sidehack's.

this is a good point  2 guys with 2 helpers build :

1000 1 chip usb sticks  
500   2 chip usb sticks
200  10 chip boards


that may be all of sidehack's production over the next month.

If bitmaintech was doing them

that would be 1 days production.

Completely different set of cost accounting for the same builds and same chips due to 30x the volume.


To others reading the above is a fictional estimate not based on anything but a guess.

[sidehack]

So, got some new charts for y'all.



I got to thinking about some of the design choices on the regulator, specifically FETs and operating frequency. I'd been working around 600KHz previously, and the new buck driver had stock setpoints at 500KHz and 670KHz so I opted for 670. Going up in frequency keeps inductor ripple current low, which keeps output voltage ripple low with a given output capacitor ESR. It does, however, introduce increased losses from gate drive switching. So I figured I'd test at 500KHz (where the inductor ripple was still pretty reasonable) and I saw an increased efficiency.
Then I got to looking at the FET transition times compared with the dead times from the controller. If your rise and fall times are long, this increases conduction losses from operating in the linear region (between full-off and full-on). If the delay times are too long, you can get shoot-through losses when both FETs are temporarily on. The FETs we had spec'd for our Chuckwagon project had better transition times, though the delay times weren't that much better. They also had a slightly lower Rdson, which is to say the on-state resistance. The power losses in the top FET, since it's only on about 15% of the time, are dominated by switching losses. The bottom FET, however, is on the other 85% of the time so its conduction losses (resistive losses, current squared times Rdson) dominate the switching losses. The Chuckwagon FETs have a higher gate charge, which increases switching losses in the top FET, but between the lower shoot-through losses and the lower conduction losses in both the top and bottom FETs, I still saw a net efficiency gain over the original FETs at 500KHz. A side benefit was, for some reason the output noise was much better. Possibly this is because of reduced switching noise or shoot-through currents, but the output was cleaner even than all of my tests with the first regulator design (the IR3899). So, it adds about a quarter to the total cost to use the different FETs but I'm pretty sure the benefits outweigh the costs.

Especially when I can operate it at 606mV 150MHz 8.25GH/s with 500mA draw on the port.

[HolgerDansk]

@sidehack

Thank you for sharing your skills and effort on this project.  I think it is a great idea, to have something simple and low cost that people can learn with. 

Although have an S2, S5's and had some S3+ miners, I've never dared to tinker with them.  I don't want to mess up a miner that I had to pay that much for (nor void a warranty).  This will be something perfect that I can try different things with.

Great work.  Keep it up!

[Dexter770221]

Also, many power coils don't like higher frequencies. Core losses increasing dramatically when frequency is above sweet spot. At coilcraft website is nice tool to compare their coils. You may set freq, current and see some nice graphs

[sidehack]

I'm not sure how stable the buck driver was at the higher frequency either. My outputs I was seeing pulses in the 800KHz neighborhood. The inductor behaved well at 600KHz off the IR3899.

But yeah, reducing core losses in the inductor was likely a contributing factor in improved efficiency.

[CanaryInTheMine]

<snip>

600mV	GH	Iin	Pin	W/GH
100MHz	5.5	372	1860	0.34
125MHz	6.88	448	2240	0.33
150MHz	8.25	511	2555	0.31
625mV
100MHz	5.5	390	1950	0.35
125MHz	6.88	464	2320	0.34
150MHz	8.25	544	2720	0.33
175MHz	9.63	620	3100	0.32
200MHz	11	704	3520	0.32
650mV
100MHz	5.5	410	2050	0.37
125MHz	6.88	495	2475	0.36
150MHz	8.25	575	2875	0.35
175MHz	9.63	660	3300	0.34
200MHz	11	760	3800	0.35
225MHz	12.38	850	4250	0.34
250MHz	13.75	945	4725	0.34
675mV
100MHz	5.5	440	2200	0.4
125MHz	6.88	530	2650	0.39
150MHz	8.25	610	3050	0.37
175MHz	9.63	715	3575	0.37
200MHz	11	810	4050	0.37
225MHz	12.38	915	4575	0.37
250MHz	13.75	1020	5100	0.37

 <snip>
these are really fucking good numbers.  <snip>

Haha, I love your display of enthusiasm!! It's not often I see you using such language

[buysolar]

Wow this is so exciting. Looks like I might actually get to upgrade the rest of my old S1's!! Can't wait. These days I only run them when it is cold outside. You guys are awesome. So much fun coming down the pike. I had a great time upgrading a couple of my S1's to S3's with my daughter (she got a big kick out of taking everything apart and putting it all back together and seeing it work) but then bitmain discontinued sales of the upgrade kit the second I got the two upgrade kits I ordered working properly. Really looking forward to sitting down with my kid again and upgrading the other couple dozen S1's I have left.   
Godspeed to you all!!!

[AJRGale]

this is making me want to get my fluke clones and see why my dodgy "New R-Box" is dodgy, i think i have schematics somewhere...

none the less, a handful of these single chips would probably fit easily over the rbox's heatsinks, and probably out preform the be200s..

actually, i wonder :-? could i just squirt these BMs in the same place? where's my hax-saw, $5 solder-blobber and 10-gauge wire...

[sidehack]

I have about half a dozen New R-Box on the shelf that we got busted off CrazyGuy and rebuilt. Those are nice little units, and kinda meet the same niche that we'd like to do with individual TypeZero boards.

[AJRGale]

to bad rockxie canned the business and went following friedcat into the not so, but similar flavoured, gaw hell... he was doing good for a while there, then greed kicked in i thinks.

if you can fill that void, many people would be happy, Bring the mining back to the people!

[sidehack]

Bring the mining back to the people!

That is one of our primary goals, always has been. Slow starting on account of we won't take in investor, speculation or dev-preorder money out of principle, but hopefully we can get rolling here soon. First thing in the morning Novak and I need to give the Compac PCB a once-over, and if it checks out we'll be ordering prototypes. With any luck, two weeks from now we'll have sample units in a few hands for testing and review.

[philipma1957]

Bring the mining back to the people!

That is one of our primary goals, always has been. Slow starting on account of we won't take in investor, speculation or dev-preorder money out of principle, but hopefully we can get rolling here soon. First thing in the morning Novak and I need to give the Compac PCB a once-over, and if it checks out we'll be ordering prototypes. With any luck, two weeks from now we'll have sample units in a few hands for testing and review.

Good I am bored out of my mind without any new gear to play with.  Fingers crossed.

[notlist3d]

Bring the mining back to the people!

That is one of our primary goals, always has been. Slow starting on account of we won't take in investor, speculation or dev-preorder money out of principle, but hopefully we can get rolling here soon. First thing in the morning Novak and I need to give the Compac PCB a once-over, and if it checks out we'll be ordering prototypes. With any luck, two weeks from now we'll have sample units in a few hands for testing and review.

Good I am bored out of my mind without any new gear to play with.  Fingers crossed.

That would be great! I am the same way.  Although this weekend if all goes as planned my new mining area will keep me busy setting it up.  Have networking ran to it.  Now just need to run a 9 electrical cables.

[philipma1957]

Bring the mining back to the people!

That is one of our primary goals, always has been. Slow starting on account of we won't take in investor, speculation or dev-preorder money out of principle, but hopefully we can get rolling here soon. First thing in the morning Novak and I need to give the Compac PCB a once-over, and if it checks out we'll be ordering prototypes. With any luck, two weeks from now we'll have sample units in a few hands for testing and review.

Good I am bored out of my mind without any new gear to play with.  Fingers crossed.

That would be great! I am the same way.  Although this weekend if all goes as planned my new mining area will keep me busy setting it up.  Have networking ran to it.  Now just need to run a 9 electrical cables.

pictures please post them in your fans thread   https://bitcointalk.org/index.php?topic=1020826.0


@ sidehack It has been a pleasure reading this thread and watching this grow.  Thanks for giving me something to look forward to in mining gear.

[HerbPean]

I have 3 S3 ready for upgrade but i will also try to find old cheap S1 to udgrade them with your boards.

Fun times ahead !!!

[OgNasty]

With any luck, two weeks from now we'll have sample units in a few hands for testing and review.

[alh]

Bring the mining back to the people!

That is one of our primary goals, always has been. Slow starting on account of we won't take in investor, speculation or dev-preorder money out of principle, but hopefully we can get rolling here soon. First thing in the morning Novak and I need to give the Compac PCB a once-over, and if it checks out we'll be ordering prototypes. With any luck, two weeks from now we'll have sample units in a few hands for testing and review.

Considering the damage BFL has done, you might want to replace a 2 week estimate with something more like 3, even if 2 is more accurate. While this is obviously hugely more transparent than BFL, I am afraid they may have ruined the phrase "Just two more weeks".   

[philipma1957]

Bring the mining back to the people!

That is one of our primary goals, always has been. Slow starting on account of we won't take in investor, speculation or dev-preorder money out of principle, but hopefully we can get rolling here soon. First thing in the morning Novak and I need to give the Compac PCB a once-over, and if it checks out we'll be ordering prototypes. With any luck, two weeks from now we'll have sample units in a few hands for testing and review.

Considering the damage BFL has done, you might want to replace a 2 week estimate with something more like 3, even if 2 is more accurate. While this is obviously hugely more transparent than BFL, I am afraid they may have ruined the phrase "Just two more weeks".    

two week wait time shall be replaced by "about one fortnight's waiting period" .