Take with a grain of salt, I mine in linux and haven't tried any of the Windows OC tools.

My experience is that the 6xxx series cannot underclock the memory further than CPU clock minus 125mhz in software.  Attempting to do so will set the 'peaks' properly, but the card simply reverts to the default memory clock. 

I run mine at 885 GPU / 760 RAM for example, and can't push the memory clock any lower with software.

I believe a BIOS flash should allow underclocking the memory further. I attempted this but stopped after a failed attempt when I was short on time.  I set the default clocks to 885/300, it seemed to boot fine, but got immediate BSOD rebooting into to Windows.  This indicates to me that a) the flash probably worked fine, and b) ATI drivers in Windows took a dump upon seeing the weird out-of-spec clocks.  I didn't have time then (or now unfortunately) to see if the linux drivers would accept the new clocks.

Perhaps someone with experience flashing alternate clocks / voltages to 6xxx series cards can chime in?

People here are so generous

Added to my sig. since I keep getting asked for it

Performance should be basically identical, they both started from AMD reference designs and likely didn't muck with anything but PCB positioning and the BIOS.

XFX does have a great warranty, and from what I've read they're pretty relaxed about replacing pebkac issues like hosing the BIOS (at least in North America)

I have 4 of the XFX cards and get ~360mh/s like you mentioned of the Sapphires, so that's probably proof enough.

I have a couple of Sapphire 5830s that are solid cards as well, both manufacturers seem to have their siht together.

For me (if i buy more cards anyway) it comes down to this:

$ / performance
Warranty
Cooler design

The ideal card for me in that case is an XFX 6950 with a standard turbine fan cooler (sucks air in the rear of the card, blows out the back of your case).  Unfortunately that card doesn't exist - virtually all of the 1GB 6950's use multi-fan or blow-everywhere style coolers.  Several of the 2GB models do, but the extra VRAM isn't worthwhile for mining.

A little electrical tape over the exposed connector goes a long way to solving that, and helps keep loose extenders in place to boot

Misunderstanding, we are talking about the same thing.  See my edit above.

That 93% efficiency figure will be at a particular load, take a look at the efficiency graph for the beloved Corsair AX1200 (also 80+ gold) for an example:

http://www.corsair.com/ax1200.html

[edit] I see where I was unclear,  what I should have said is that the PSUs max efficiency will be at 50-70% of its maximum load, not that it would only be 50% efficient.  80+ means at least 80% efficient over all loads.

USB2 works great for most linux distros.  Most of the system will be running in RAM, not from the USB directly, so read/write speeds don't come into play often.  Especially for a dedicated miner.  Only thing to watch out for is if you plan on keeping log files; write them out to a network share instead of the USB drive.


Your 1000W PSU should handle them pretty well.  A really big OC on a 5830 might push 180W / card.  Not sure about your 6870's, but I can't imagine it's much more.  If you've got a kill-a-watt or something else to measure power at the wall, it's easy to see how much headroom you've got after the 6870's are in.

[edit] Just re-read and saw you're considering 2x 600 or 700W PSUs - this isn't a bad option at all, but I'd do a price comparison.  If you're going to have 4 cards eventually, and the power usage of those cards fits in <= 800W or so, I'd just go with a 1000W.  If it were 4 6990's on the other hand (350W+ each!) I'd go with multiple PSUs.  Remember your max efficiency is going to be around 50-70% of the advertised PSU wattage.


If this is going to be a dedicated miner, and you don't have the components already, I'd look at something with more PCIe slots.  3 * 16x slots is great, but you don't need that bandwidth for mining.  You'll find there are much cheaper options with 2 * 16x and 2 * 1x slots, which will work well with extenders.  More than 2 * 16x slots and you're entering 'extreme gamer territory' where prices climb quickly.

Not for long   You'll find out quickly that these rigs make excellent space heaters.  I plan to duct mine into my furnace this winter to warm the whole house.

6870 is overpriced for mining, +$50 USD over the 5830 which has the same number of shaders.

Go for the 5830, or go for the gusto and reach into the 6950/70/90 area.

You'll probably want to do some experimentation on case vs caseless; if you're going to have a harddrive or other moving components (other than fans, those should run fine), you should probably use a standard PC case. 

If you can boot from USB or the network instead, go caseless - with ambient temps like those you'll get some pretty nice wintertime overclocks

I got about 20mhash on an Opteron 6128 (8 core), so you've got a maybe 40-50% more than that per cpu. 

If they're doing nothing else, you didn't have to pay for rent, electricity or internet access, I'd say fire 'em up.

Realistically though all that processing horsepower will just dig you a nice hole

It's hit or miss whether or not the shaders will be available on any given card, even two cards in the same model/revision.

Nobody knows for certain how the shader cores are disabled on these cards, the people insisting 'laser cut' are talking out their ass or parroting someone else who was talking out their ass

When you see 'laser cut' you can assume this to simply mean 'disabled in hardware' until someone can confirm.

It's also possible the disabled shader cores are simply non-functional on many of these cards, bottom-binned so to speak.

Good to know

I'd recommend the last extender in the chain be one with the molex power adapter; a longer chain = higher resistance = more heat in the wire, which could potentially cause some fire-like problems when they're pushing 75W from the mobo socket.

Used the 'bubblegum' mod on one of my XFX 1GB 6590 ZDNC, worked like a charm but it's a big PITA to get placement right!

Instead of bubblegum, I used a chunk of window sealant putty and a bit of solid-core ethernet wire, works the same and you don't have to chew on it first

Shaders didn't unlock but the flash took with no problem at all.

I'm going to pick up one of these circuit-write pens instead for the other 3 cards: http://www.radioshack.com/product/index.jsp?productId=3964901

Because you asked

See normal 1x to 1x extender:
https://cablesaurus.com/index.php?main_page=product_info&cPath=1&products_id=8

Versus 1x 'to 16x' extender (the socket is simply modified to allow the 16x card to seat):
https://cablesaurus.com/index.php?main_page=product_info&cPath=1&products_id=10

All the important stuff happens at the head end of the connector, the rest of the pins in 4x, 8x or 16x just enable greater bandwidth. 

In short, don't overpay for a 1x to full-length 16x adapter that fully seats your card; the extra pins aren't connected to anything, and your 16x card will work perfectly fine connected to only 1x pins.

[note] no affiliation with cablesaurus, just links I had handy

Without knowing more, assuming this is a dedicated miner, offhand suggestions are

- boot from USB or network, no internal drives
- maximize cooling to reduce speed or even remove fans
- use a cheap single-core CPU (eg Sempron 140 @45W / Celeron 430 @35W)

If your mobo has a good bios you can reduce memory clocks, possibly voltages on your system RAM as well (disclaimer: may break stuff, ymmv, /notmyfault).  The only thing that needs to perform well to hash are the GPUs, spin everything else down as long as it's stable.

None of this will garner big results, but every little bit adds up over time.

/goes off to implement his own suggestions  

The green+black pins intercept the power switch to tell the PSU when to turn on.  If they were female heads, you'd just plug those pins into a second PSU to turn it on simultaneously.

Male heads?  Might have come with a case with more than one power button, a daughter board, or maybe attached to a smaller special-purpse PSU (to turn on fans, water pumps, etc)

Perhaps one of  those 'dual' PCs that pair a beefy, power-greedy PC with a second, light, low-power computer built in - it would allow the smaller computer to power on and off the larger one at will.

So in short, no idea

None at all for mining.  Gaming on the other hand..  The only difference between PCIe 1x and PCIe 16x is the amount of bandwidth available to the card.  Mining uses very little bandwidth, and so PCIe 1x works just fine.

Er.. no.. what I'm talking about is connecting two together.. eg, two 12cm extenders become one 24cm extender.

If you're asking about chaining them, at some point you're going to reach a too-high signal to noise ratio and the card will either act funny or not be recognized.

I don't have experience with them, and I'm not very familiar with PCIe specifications, so this could be 20" or 20 feet..

Every coupling you make (by chaining them) will degrade the signal slightly at the very least.

That's not quite right, and that thread has not come up with a method to hard-mod shader unlock quite yet, but someone who's good at tracing the leads may be able to find the anomaly and 'bridge the gap' so to speak.

That thread only shows how to jumper the write-protected BIOS to allow you to flash, it's hit or miss whether or not you'll actually be able to unlock the shaders.

Arctic has a few other options: http://www.arctic.ac/en/p/cooling/vga.html

Oddly the frontpage shows the PRO as 5870 compatible on the front page, but neither the PRO nor PLUS list it in the detailed compatibility lists.

They have a 3-fan 'Arctic EXTREME 5870' which appears to be tailored to your card, with 250W heat dissipation.  Unfortunately the fan-cooler-card sandwich appears to make the card 3 slots thick.

You can probably improve the performance with a a better 92mm fan - the ones included on the PRO/PLUS are only 27CFM.  I'm sure they're quiet, but an eg. 40CFM fan wouldn't be too terribly loud and might increase that heat dissipation by ~30-40W or so.  As far as I can tell the PRO/PLUS appear to be the same damn thing, I can't see where the 20W difference between them lies.