Bitcoin Forum

Trying to understand the technicial differances between both cards...

4870x2  =1600 Stream Processors               5870 =1600 Stream Processors

 85 Mhash/s Core 0  56-70 Mhash/s Core 1                  350-390 Mhash/s Core 0

 DDR3 with a 256x2 (512-bit bus)                                DDR5 with 256-bit bus 

 ROP's 16x2 (32)                                                        ROP's 32

 Texture Units 40x2 (80)                                             Texture Unites (80)

 32-bit floating point                                                   32-bit floating point
           
In nearly all directx 9 and 10 games the 4870x2 and 5870 are Neck in Neck.


It puzzles me that the 4870x2 does so very bad in compairison to the 5870 when memory speed and bandwith are absent requirments... only raw processing power is needed.  I would expect to lose a certain percentage of computing effecency between core 0 and core 1 on the 4870x2 but to have a 250% preformance difference in these 2 video cards?


Maybe we need someone who can write custom drivers or an application profile for bitcoin mining? Owning 4 of these cards myself, I would be willing to put up a bounty.

This post (http://forum.bitcoin.org/index.php?topic=12505.0) should explain how to get your second core up to speed.  I don't, however, have an answer about why it is slower than the 5870.

The 5870 includes more capabilities for compute since most of the miners were based on open cl it's that performance that's important.

From what I understand... the HD4800 series has plenty of horsepower for OpenCL applications... unfortunately it was produced before OpenCL was fully developed. Hence there's some math functions that are virtualized in the Graphics cards main memory pool, and not the local caches that are in the core.

Which is why an 800SP 5770 walks all over an 800SP 4850,70,90 in terms of hashrate, and not necessarily graphics performance.

And mind you this is in general terms, I looked and I can't quote the article I read it in. But I was interested why the HD3000 series couldn't run OpenCL apps at all (no local cache, if you were wondering.)

I know it really sucks. You're better off selling all 3 4870x2s and getting two 5xxx cards. I only have one but I think I may just pony up the difference.