help 2 x 7970 going faster than 3 x 7970

[cryptohunter]

this is weird, i have always just had 2 x 7970 hashing away at 740kh each in my rig. So now I've updated to 3 x 7970 all the same brand and model they will only hash at 640kh each ? this is using the same settings in cgminer and msi afterburner.


What is happening with that? the psu are 1250W so should be enough power easily?

[antgrinder]

the PSU should have enough power. Try to make adjustment to your settings

[cryptohunter]

the PSU should have enough power. Try to make adjustment to your settings

Yeah, i have tried everything, perhaps 8gig of ram is not enough for 3 cards?

[rayfloyd]

By any chance did you buy Sapphires VApor-X 7970, if so you gotta flash the bios to go into the 750 kh/s range

[Desensitizer]

What are your temperatures? Could the cards possibly be throttling back automatically due to how hot they are getting as a result of the added cards? Also, did you install new drivers or any other software that might have changed hash rates with the cards?

[ccjk]

Try this

{
"pools" : [
{
"url" : "stratum+tcp://xxxxx:3333",
"user" : "xxxx",
"pass" : "xxxx"
},
{
"url" : "stratum+tcp://xxxxx:3333",
"user" : "xxxx",
"pass" : "xxxxx"
}
]
,
"intensity" : "19",
"vectors" : "1",
"worksize" : "256",
"kernel" : "scrypt",
"lookup-gap" : "2",
"thread-concurrency" : "22400",
"shaders" : "2048",
"api-port" : "4028",
"expiry" : "120",

"gpu-platform" : "0",
"gpu-threads" : "1",
"hotplug" : "5",
"log" : "5",
"no-pool-disable" : true,
"no-submit-stale" : true,
"queue" : "1",
"scan-time" : "30",
"scrypt" : true,
"temp-hysteresis" : "3",
"shares" : "0",
"kernel-path" : "/usr/local/bin"
}

[aznatama]

This is a BTC forum, but seeing that nobody can read and/or don't care... I'll respond anyways...


Make sure you're powering your cards from SEPARATE RAILS, and that you're ensuring each card has enough power (COUNT how many +12v wires are going from your PSU to your card, since each line can only carry so much load).  It doesn't matter if you ahve a 1250w PSU if you're loading multiple cards on a single rail.  The Seasonic 1250 has 4 rails, you should have no more than one car per rail.

Also, post your settings.  For LTC, you should be undervolting your GPUs so that you draw less power.

I have 2x 7870's in a standard PC tower, both running very quiet, at a smooth 363 kh/s, <75C, ~1500 fan speed.  Undervolting will help reduce load on all your components and reduce heat/noise as well.  No effect on hash rate either.