Hold up I think I confused you with the intensities. In my experience bitcoin and the SHA-256 altcoins need low intensity (much less than 10, as I said mine are around 4 or 5) but with scrypt (litecoin and so on) you need to use much more than 10, probably up near 15. You need to test these yourself eg start at say 10 then do 11 then 12. Write yourself a table on a notepad comparing the performance at each step.
From the SCRYPT-README.TXT file in cgminer:
Just like in bitcoin mining, scrypt mining takes an intensity, however the
scale goes from 0 to 20 to mimic the "Aggression" used in mtrlt's reaper. The
reason this is crucial is that too high an intensity can actually be
disastrous with scrypt because it CAN run out of ram. High intensities
start writing over the same ram and it is highly dependent on the GPU, but they
can start actually DECREASING your hashrate, or even worse, start producing
garbage with HW errors skyrocketing. Note that if you do NOT specify an
intensity, cgminer uses dynamic mode which is designed to minimise the harm
to a running desktop and performance WILL be poor. The lower limit to intensity
with scrypt is usually 8 and cgminer will prevent it going too low.
SUMMARY: Setting this for reasonable hashrates is mandatory.
And also entirely relevant to your interests:
---
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 1141 --gpu-memclock 1875 -I 20
for a hashrate of 745kH.
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 22392) 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!
If you decide to declare a value for thread concurrences (instead of just declaring shaders) but run into problems with really high values, you might find that for your card you require "setx GPU_MAX_ALLOC_PERCENT 100" that you'd normally have in your batch file, you can still use the config file if you add GPU_MAX_ALLOC_PERCENT 100 as a windows environment variable. Right click on my computer -> Properties -> Advanced system settings -> Environment variables -> In the "User variables for (username)" click New and then add GPU_MAX_ALLOC_PERCENT and set the value to 100 It might vary from OS to OS but generally you should be able to find it in advanced system settings.
