Gigabyte Z87X-OC1:
GPU's MODEL NAME: 2x Sapphire R9 280X Dual-X
VRAM:3GB
CORE/MEMORY CLOCK: 1100/1600
HASHRATE: Average: 270 Sols/s
MINER SOFTWARE: Claymore's AMD GPU Miner v12.0
OS: Windows 10 Professional, AMD 17.2.1 Drivers


Gigabyte Z77X-UD3H:
GPU's MODEL NAME: 1x Asus R9 280x DirectCU2
VRAM:3GB
CORE/MEMORY CLOCK: 1200/1600
HASHRATE: Average: 295-300 Sols/s
MINER SOFTWARE: Claymore's AMD GPU Miner v12.0
OS: Windows 10 Professional, AMD 17.2.1 Drivers

Stocks BIOS and overclocking was done in WattMan with -20% PowerLimit

You may want to check the current version of Claymore's ZCash miner - v12.0.

The temps for your 280X seem high, my clock and temp information readings are:
Asus 1200/1600, 71C Fans 41% 300Sols/s
Sapphire 1100/1600, 73C Fans 64% 270Sols/s

I set my PowerLimit for both cards to -20%

I wish I had a 7990 -those are durable as hell, the point about another fan is good also and something I forgot to mention.

I run the Sapphire 280X rig with a fan on top, even though the Sapphires can easily handle temps above 70C, the XFX 270s need help so I have two Yate Loon fans connected to each other via molex (really old fans) and into the motherboard to a standard 3-pin fan connection. The Gigabyte 270X are Windforces - totally overkill but extremely effective to keeping GPU temps under control, even in the summer without any additional cooling.

I have six Asus 280X DirectCU2 and I have issues mining with them on NiceHash, related to heat. When temps go above 70C I get rejected shares, all other videos cards from XFX 270, Gigabyte 270X and Sapphire 280X run without issue. I only have one Asus 280X running at 69C-70C, at 290 Sols.

The  Asus heatpipe design is good for the designated use case of a videocard but not for mining, these cards are really sensitive to ambient temperature and the default fan curve favors silence over cooling.

I'd recommend running the fans at 100% and see if you still have issues, then decrease the fan speed until while maintaining a constant GPU temp of 69 or lower, leave the Wattman settings at default until you can get the temp under control. You might also try try changing the voltage through TRIXX or Afterburner.

I've tried BIOS editing in the past, but didn't have much success; I will find a BIOS that had been edited for my cards. A reference 290 BIOS should be fairly common and easy to acquire. I like the idea of keeping what I have and tuning for efficiency until I can get a 470 or two.

On the 290 reference cooler, I would have to run the fan at 100% all the time but it was sufficient to keeping the card cool enough to mine. I just may convert one of them over then and see, thanks!

Thanks you all for the great comments, advice and observations so far!

Hawaii
There is a general consensus to keep the Hawaii series cards, when they are not throttling from heat, the cards perform very well. I purchased Tri-X fans and heatsinks to replace the reference style blower cooler, I'll update the progress of this once I receive the fan and heatsink combo.

RX 470
I'm not able to use all of my gear due to not having enough circuit power (yep, noob mistake made) so I'll put everything up for sale and see what sells at a price I can live with. As I sell, I'll look to either outright purchase of BTC or getting 470s (most likely)

Gigabyte
Greg, the 270X have performed well and stayed cool and were survived mining LTC back in the day, my frustration with Gigabyte in general is that they are voltage locked and unlike Asus, they probably use the OEM reference PCB design and chip specs. The 270Xs have been solid, but I did have Windforce 290s that were eventually upgraded to 390s through Gigabyte warranty which I thought was very generous but the 290s did go back to Gigabyte several times for repairs. I think your opinion is a valid point because the cards seem fine for normal use but in the case of my 290s they didn't survive very long despite having a Windforce heatsink and triple fans.

Asus
270X and 280X are well built but they both throttle due to poor heatsink design and a fan curve that  favors silence over performance, voltage can be adjusted -100mv using GPU Tweak.

So Far...
Keep the reference 290s and convert the blower style cooler to a Tri-X if possible, keep the 390s.
I'll continue to use the 3X Gigabyte 270X and 2X Sapphire R9 280Xs for mining on NiceHash, and start selling off the rest of the gear.

Thanks!

Unfortunately, cost of electricity here is 0.11kWh. Right now I use a single 390 for sporadic mining, it does 344 Sols. A single Gigabyte 270X does 500 h/s (cryptonight) I have three  running 24/7 on NiceHash.

I'd like the idea of getting more energy efficient cards but I feel like I have to get the most of what I currently have and it seems like the market is saturated with old cards at the moment.

What type of 470s would you recommend?

I've been renting out my hashrate on NiceHash and the Sapphires have been solid performers with respect to mining but I was unable to lower voltage via TriXX. The Asus 280Xs can be dropped to 1100mv in GPU Tweak but actually fluctuate to 1148-1150mv; Between the two, the Sapphires perform consistently better due to the fan curve being more aggressive and the heatpipe and cooling being simpler but better than the Asus it seems.

Hello Everyone,
I mined some LTC a few years ago but had to stop. I want to start mining again and have the following gear:

2 X Sapphire 280X Dual-X OC 3GB
6 X Asus 280X DirectCU2 TOP 3GB
3 X Gigabyte 270X Windforce 2GB
4 X Asus 270X DirectCU2 TOP 2GB
2 X Visiontek 290 Reference 4GB
2 X Gigabyte 39o 8GB
2 X XFX R9 270 DoubleD

Are any of these still power efficient enough to mine compared to a 470/480?
Would it be better to sell all of these at a loss and just buy BTC directly?
I have enough circuit power to use 1/3 of the gear, what do I keep and what do I sell off?

I need help and would appreciate any advice, thanks!

I'm not having issues with systems populated with Sapphire 280X and XFX 270s, but I am just using stock BIOSs and no changes in WattMan. Workrates remained the same.

I've just got back into GPU mining. I'm using NiceHash Miner v1.7.4.3 (Windows 10 Pro) in various configurations and am not having any issues but these configs are not really optimized.

AMD Driver 17.1.2
2 - R9 Sapphire Dual-X OC 280X
495 Sols/s equihash

AMD Driver Version 17.1.1
1 - Gigabyte Windforce R9-270X OC
464 H/s cryptonight

AMD Driver 16.11.5
2 - XFX R9 270 DD
300 Sols/s equihash