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Date: Wed, 12 Aug 2020 07:41:07 -0800
From: Royce Williams <>
Subject: Re: sha512crypt-opencl / Self test failed (cmp_all(1))

On Thu, Aug 6, 2020 at 5:21 AM Solar Designer <> wrote:


On Wed, Aug 05, 2020 at 09:45:26PM -0800, Royce Williams wrote:
> > When this happened to me, I dropped the speed on the specific boards by
> > 10MHz or so until it stopped,
> When errors are infrequent, it's generally more efficient to just let
> them happen once in a while, giving a higher average c/s rate than you'd
> have at a lower clock rate.

Indeed. There's definitely a sweet spot there. I'm sure that the various
Bitcoin forums from ZTEX have similar wisdom.

> > using the "Frequency_[serial] = 999" syntax
> > for that particular algorithm's section.
> >
> > If enough boards are lower than the default, it's easier to just change
> the
> > default and create exceptions for the remainder.
> Please remember that there's generally no point in adjusting frequencies
> per board (except for testing) if you use all of your boards as one big
> cluster.  John is currently only able to use the boards synchronously,
> so the slowest board will determine the cluster's overall performance.
> This changes when you use "--fork" or "--devices", but in particular
> with "--fork" it'd probably be inconvenient for you to have some forked
> processes terminate much sooner than others.  So the per-board frequency
> adjustment is generally only useful when you run per-board-set attacks,
> explicitly targeting attacks to same-frequency lists of "--devices".  Of
> course, you'd also use "--session" to launch multiple attacks from the
> same "run" directory.

Ah, yes - I'd been tuning relative to "--fork" ... once I re-discovered it.

In my experience, for contests and similar time-critical scenarios, having
some boards finish sooner also means (theoretically) getting some *results*
sooner - which may be worth the inconvenience.


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