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Author Topic: Radeon 6790 vs 6770 - what are they??  (Read 2934 times)
catfish
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September 25, 2011, 05:57:53 PM
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Obviously these are low end cards, and I've been so disappointed with my 6870 that I'm unlikely to start buying the 67xx series. But my curiosity was piqued by these two particular cards.

The 6770 is pretty popular and is available on most online UK stores for around £90. These seem to be clockable to run at around 200-220 MH/s safely. This is what I get from my 5770s, which are cheap (£70) and critically, only take up one slot (XFX single slot version) and one PCIe power cable.

However, the 6770 is advertised as needing NO additional PCIe power. Is this correct? Getting 200 MH/s without taking up another precious PCIe power cable seems pretty damn impressive to me.

But I've just come across an advert in the same supplier (CCL) for the 6790 card. This is priced very closely (£99).

Checking the Mining Hardware Comparison, the two sole entries for the 6790 claim 220 and 219 MH/sec. I get this from my 5770s, and there are entries for the 6770 that match these number too.

BUT... the 6770 has 480 stream processors. The 6790 is advertised as having 800 stream processors, and needing two PCIe power cables!!!!

So what the hell is this card? Is it some old-tech badly packaged (why two PCIe power? Even the 5770, which can run faster, only has one), or is this card potentially a bargain that has been overlooked by everyone... and can do a hell of a lot more than 220 MH/sec?


After all, if it's the same core technology as the 6770, which can pull 210 MH/sec from 480 stream processors, then with 800 stream processors and a higher core clock, I'd expect much higher hash rates.

Does anyone know? I'm intrigued. Almost intrigued enough to buy one...

...so I give in to the rhythm, the click click clack
I'm too wasted to fight back...


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scifimike12
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September 25, 2011, 06:13:46 PM
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I think you're getting mixed up with your card model numbers.

6770 → 800 SP, 128-bit bus, 850MHz core, 1 x 6-pin PCIe
6790 → 800 SP, 256-bit bus, 840MHz core, 2 x 6-pin PCIe

The 6770 is about that of a 5770 like you had mentioned.

I think you're getting mixed up with the 6670 which has 480 SP and doesn't require an additional PCIe power cable.
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September 25, 2011, 06:34:15 PM
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as far as the gpu is concerned the 6770 is no diffrent than a 5770 it's a rebadge, the 6790 is a cut down 6850.

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September 25, 2011, 06:35:10 PM
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First of all, a 6770 is simply a rebranded 5770 (with some bios tweaks allowing better HDMI support).

Secondly, a 6770 has a TDP of 108W. That would require at least one 6 pin connector (the motherboard can only supply 75W).

Perhaps there are 5770/6770 cards out there that are undervolted and underclocked to get below 75W, thereby not needing the power cable, but their performance would drop accordingly.

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September 25, 2011, 08:01:38 PM
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Did some more research. No mixup on my part - however a monster mixup on the part of the retailer! Completely wrong specs on the 6770 - no idea which card they were mixing it up with...

Given that the 6790 has the same core as the 68xx series, it initially sounded promising (i.e. BIOS hack to re-enable the disabled stream processors), but apparently AMD have done a proper laser-destroy (what a waste eh?) to prevent the unlocking that I've already done to all my 6950s Wink

What is more important is that the research I did led me to find out that my disappointing-as-a-bitcoin-miner 6870 card can be made to work properly in my Mac Pro, which is currently running a 4870. This is a big deal and will save me a fortune (was considering spending £350 on an Apple-specific 5870)... Smiley

...so I give in to the rhythm, the click click clack
I'm too wasted to fight back...


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deslok
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September 25, 2011, 08:04:53 PM
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Did some more research. No mixup on my part - however a monster mixup on the part of the retailer! Completely wrong specs on the 6770 - no idea which card they were mixing it up with...

Given that the 6790 has the same core as the 68xx series, it initially sounded promising (i.e. BIOS hack to re-enable the disabled stream processors), but apparently AMD have done a proper laser-destroy (what a waste eh?) to prevent the unlocking that I've already done to all my 6950s Wink

What is more important is that the research I did led me to find out that my disappointing-as-a-bitcoin-miner 6870 card can be made to work properly in my Mac Pro, which is currently running a 4870. This is a big deal and will save me a fortune (was considering spending £350 on an Apple-specific 5870)... Smiley

Dude apple specific, buy a cheap motherboard and make a linux(or er um acquire windows) rig

"If we don't hang together, by Heavens we shall hang separately." - Benjamin Franklin

If you found that funny or something i said useful i always appreciate spare change
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catfish
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September 25, 2011, 09:21:51 PM
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Did some more research. No mixup on my part - however a monster mixup on the part of the retailer! Completely wrong specs on the 6770 - no idea which card they were mixing it up with...

Given that the 6790 has the same core as the 68xx series, it initially sounded promising (i.e. BIOS hack to re-enable the disabled stream processors), but apparently AMD have done a proper laser-destroy (what a waste eh?) to prevent the unlocking that I've already done to all my 6950s Wink

What is more important is that the research I did led me to find out that my disappointing-as-a-bitcoin-miner 6870 card can be made to work properly in my Mac Pro, which is currently running a 4870. This is a big deal and will save me a fortune (was considering spending £350 on an Apple-specific 5870)... Smiley

Dude apple specific, buy a cheap motherboard and make a linux(or er um acquire windows) rig
Huh

My business uses exclusively Macs. I've got 11 in this office I'm sitting in now.

However, just for the lulz, I've also got phoenix running on my main workstation (Mac Pro) which is netting a monstrous 80-90 MH/sec Smiley

The rest of the 6 GH/sec are from the dedicated mining rigs. You may have seen my 4 frame rigs in the 'pictures of your mining rigs' thread... Right tool for the job is my motto, hence the dedicated miners use Linux.

What I was getting at was that I've bought one 6870 for my dedicated miners, found it wasn't particularly great, but can re-purpose it as the main GPU in my Mac Pro, which is currently a weak 4870. I'll get a substantial upgrade to my Mac without having to fork out for an expensive Apple-specific card. The Apples aren't used for bitcoin mining (other than to take advantage of the Mac Pro when it'd not doing much else).

I am far too old for operating system religious wars, but I can assure you that the cost of the time lost if I were to switch all the OS X boxes to Windows or Linux would massively outweigh the increased upfront cost of the Macs (other than the Mac Pro, which *at the time* was the cheapest dual-Xeon workstation-class box around).

For dedicated mining, though - Linux all the way. Why the hell would one choose anything else, unless one was only expert with Windows? The only argument for Windows mining boxes, AFAICT, is that the overclocking utilities are more mature and have more functionality than the Linux ones. As to the OS X utilities.... rofl! I absolutely love Mac OS X, but I'm not blind to its shortcomings.

Incidentally, I read in another thread on this forum a while back how 'Apple had really screwed OpenCL' - given that OS X uses OpenCL internally, and without any overclocking or tuning of the GPU, I'm getting nearly 90 MH/sec out of an Apple-clocked (i.e. underclocked) Radeon 4870... perhaps the OS X implementation of OpenCL isn't as bad as most think? Not wishing to start a flamewar here, of course.

...so I give in to the rhythm, the click click clack
I'm too wasted to fight back...


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