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Add example 7970 tuning for scrypt in readme.

nfactor-troky
Con Kolivas 12 years ago
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      SCRYPT-README

67
SCRYPT-README

@ -166,7 +166,74 @@ For example, a 7970 running with the following settings:
was using 305W! was using 305W!
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TUNING AN AMD RADEON 7970
Example tuning a 7970 for Scrypt mining:
On linux run this command:
export GPU_MAX_ALLOC_PERCENT=100
or on windows this:
setx GPU_MAX_ALLOC_PERCENT 100
in the same console/bash/dos prompt/bat file/whatever you want to call it,
before running cgminer.
First, find the highest thread concurrency that you can start it at. They should
all start at 8192 but some will go up to 3 times that. Don't go too high on the
intensity while testing and don't change gpu threads. If you cannot go above
8192, don't fret as you can still get a high hashrate.
Delete any .bin files so you're starting from scratch and see what bins get
generated.
First try without any thread concurrency or even shaders, as cgminer will try to
find an optimal value
cgminer -I 13
If that starts mining, see what bin was generated, it is likely the largest
meaningful TC you can set.
Starting it on mine I get:
scrypt130302Tahitiglg2tc22392w64l8.bin
See tc22392 that's telling you what thread concurrency it was. It should start
without TC parameters, but you never know. So if it doesn't, start with
--thread-concurrency 8192 and add 2048 to it at a time till you find the highest
value it will start successfully at.
Then start overclocking the eyeballs off your memory, as 7970s are exquisitely
sensitive to memory speed and amazingly overclockable but please make sure it
keeps adequately cooled with --auto-fan! Do it while it's running from the GPU
menu. Go up by 25 at a time every 30 seconds or so until your GPU crashes. Then
reboot and start it 25 lower as a rough start. Mine runs stable at 1900 memory
without overvolting. Overvolting is the only thing that can actually damage your
GPU so I wouldn't recommend it at all.
Then once you find the maximum memory clock speed, you need to find the sweet
spot engine clock speed that matches it. It's a fine line where one more MHz
will make the hashrate drop by 20%. It's somewhere in the .57 - 0.6 ratio range.
Start your engine clock speed at half your memory clock speed and then increase
it by 5 at a time. The hashrate should climb a little each rise in engine speed
and then suddenly drop above a certain value. Decrease it by 1 then until you
find it climbs dramatically. If your engine clock speed cannot get that high
without crashing the GPU, you will have to use a lower memclock.
Then, and only then, bother trying to increase intensity further.
My final settings were:
--gpu-engine 1157 --gpu-memclock 1900 -I 20
for a hashrate of 725kH.
Note I did not bother setting a thread concurrency. Once you have the magic
endpoint, look at what tc was chosen by the bin file generated and then hard
code that in next time (eg --thread-concurrency 22336) as slight changes in
thread concurrency will happen every time if you don't specify one, and the tc
to clock ratios are critical!
Good luck, and if this doesn't work for you, well same old magic discussion
applies, I cannot debug every hardware combo out there.
Your numbers will be your numbers depending on your hardware combination and OS,
so don't expect to get exactly the same results!
---
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