I am running simple mining OS on flash drive.....I have re-flashed it a couple times...do you think it could be a bad drive or bad flash causing this?

I am running 2x EVGA 750G PSU's per MOBO.  I have an extra one not being used.  I swapped one out at a time to check for other problems. 

Yes it also happens with three.  it just consistently drops one GPU.  Not always the same GPU.

  Sorry for the long post, however I have multiple mining rigs going and I had an issue with one rig dropping GPU's.  I have performed multiple trouble shooting steps.  I bought and installed new powered usb risers, swapped PSU's, and eventually bought a new motherboard etc...  (Biostar TB85) and I'm still having issues.  I am currently using SimpleMining (SMOS) I have pulled each GPU from the rack and installed them individually into my windows rig and ran  OCCT to test for card issues.  All are working properly.
  When I start the miner with 4 GPU's, all 4 will start mining properly for a several seconds to a minute and then it will drop one card, leaving only 3 GPU's mining.  I have also started each card individually and they all mine perfectly.  Also if I start two GPU's I get the same issue, works fine for many seconds up to about a minute and then only one GPU is left mining.   
  I appreciate any input you guys could give me on this issue.....I'm about to pull my hair out on this one!

I just upgraded my bios a couple weeks ago, could I have gotten a bad flash? should I re-flash it or maybe downgrade?

how did you fix the problem?

I'm about to lose my shit dealing with one of my rigs...I am running older equipment. EVGA Z87 FTW mobo, 2x EVGA 750G PSU's 4x R9 270X.   also using simple mining for right now.  One identical rig is running perfectly. however I have another that will start fine showing 4 gpu's and producing shares.  Approximately 1-2 minutes later it will drop to only GPU 0 (In a pci-e slot) and GPU 3 (on a usb riser) the other two cards (one connected to pci-e and one on a riser) stop mining.  I have a hard time thinking that it is a power issue due to the dropped cards being on different PSU's, and I have tried different risers without any change.  one or two minutes and they drop......Is my mobo bad?
  Any help is greatly appreciated.

Thanks for the input guys, I will order some USB risers tonight and go from there!!

would my ribbon risers work periodically and then not?

Well, I have been out of the mining game since 2012-ish.....I got every thing back up and running (kind of) and I'm having some problems dropping GPU's .....

after many days leading into weeks, I tried smos, bamt, etc.....because that is what I used before......epic fail.....so now after so much time spent, I wanted to get mining up and going, so I am using simplemining.org  here is a list of my equipment

3x EVGA Z87-FTW MOBO
9x HIS R9 270X
6x EVGA 750G PSU

My current layout is 1x gpu in a Win 7 setup that I use as a desktop, and the remaining dedicated to two rigs.

My problem is that both dedicated rigs will not work together.  The longest I have had them working together is less than 30-45 minutes.  Once it is all setup, a card (or whole rig) will sporadically drop.  Isn't always one rig or one card etc...  I have tried to troubleshoot to the best of my ability and I'm getting nowhere.......anyone ran into this before?

OK, THANKS!!! it is working....now I feel like a huge dumbass! lol... I had tried with and without the stratum+tcp but not without the "." 

so now it is only picking up 2 of the 4 cards....maybe upgrade the bios? I was looking while it was down and I do see an update....

does this make sense to anyone???

2017-07-31 09:59:06.486] [info] Connecting to stratum tcp://equihash.usa.nicehash.com:3357.
 [2017-07-31 09:59:26.507] [error] No such host: stratum tcp://equihash.usa.nicehash.com(Host not found (authoritative))
 [2017-07-31 09:59:28.318] [info] Connecting to stratum tcp://equihash.usa.nicehash.com:3357.
 [2017-07-31 09:59:48.339] [error] No such host: stratum tcp://equihash.usa.nicehash.com(Host not found (authoritative))
 [2017-07-31 09:59:51.702] [info] Connecting to stratum tcp://equihash.usa.nicehash.com:3357.
 [2017-07-31 10:00:11.723] [error] No such host: stratum tcp://equihash.usa.nicehash.com(Host not found (authoritative))
 [2017-07-31 10:00:18.005] [info] Connecting to stratum tcp://equihash.usa.nicehash.com:3357.
 [2017-07-31 10:00:38.026] [error] No such host: stratum tcp://equihash.usa.nicehash.com(Host not found (authoritative))
 [2017-07-31 10:00:47.496] [info] Connecting to stratum tcp://equihash.usa.nicehash.com:3357.
 [2017-07-31 10:01:07.517] [error] No such host: stratum tcp://equihash.usa.nicehash.com(Host not found (authoritative))
 

using optiminer-zec v1.7 zcash

-s stratum+tcp://equihash.usa.nicehash.com:3357 -u 3EWuUvtjmvRWyT9u2Hv7e1ktrBZ6Lrrvg1.itlbtu2.1 -p x

I'm about to pull my hair out with this rig.......any help is greatly appreciated.

I am having problems setting up my trial rig.  Here is my setup....

EVGA Z87-FTW MOBO
8GB RAM
EVGA 750 Gold PSU
R9 270X cards - currently using 2...but have 9 total if I ever get this setup to work...

So, here is my situation, I have been attempting to use GETH having nothing but issues with the blockchain. I have tried for a week to download the blockchain using different commands ie --fast, --rpc ..... every time I get five or so minutes in to it, my computer reboots.  It seems to be a GETH only issue.  I have deleted the block chain files and tried starting fresh etc.... I then downloaded Ethereum Wallet, to attempt to avoid issues and no avail.  I have updated drivers, downgraded drivers, tried Debian Squeeze distro's (epic fail due to Ethernet issues) and the best I have gotten to is a claymore setup using

setx GPU_FORCE_64BIT_PTR 0

setx GPU_MAX_HEAP_SIZE 100

setx GPU_USE_SYNC_OBJECTS 1

setx GPU_MAX_ALLOC_PERCENT 100

setx GPU_SINGLE_ALLOC_PERCENT 100

EthDcrMiner64.exe -lidag 0 -epool us1.ethpool.org:3333 -ewal 0x18ec1513078aa6b52b1409a05cf6b4f4820bebea -epsw x -dpool stratum+tcp://dcr.suprnova.cc:3252 -dwal Redhex.my -dpsw x



with this I get the:

GPU0/GPU1 - not enough GPU memory to place DAG
OpenCL error -61 cannot allocate big buffer for DAG
OpenCL error -38 cannot write buffer for DAG

Am I just having issues with the block chain or is it a 2GB GPU issue that cannot be resolved?

Thanks in advance for any help.......About to pull my hair out at this point...