20161106, 20:01  #2542 
"Kieren"
Jul 2011
In My Own Galaxy!
10148_{10} Posts 
THe 460 is CC 2.1. I considered the possibility that, but perhaps did not look closely enough. I just now did some searching for specific floating point capability, but despite lengthy charts in various places, I did not get the differences sorted out.

20161106, 20:27  #2543  
Just call me Henry
"David"
Sep 2007
Cambridge (GMT/BST)
16A2_{16} Posts 
Quote:
https://en.wikipedia.org/wiki/Kepler_(microarchitecture) states that consumer Kepler cards have 1/24 double precision speed. https://en.wikipedia.org/wiki/Maxwel...roarchitecture) states that consumer Maxwell cards have 1/32 double precision speed. https://en.wikipedia.org/wiki/Pascal_(microarchitecture) basically states that consumer Pascal cards have 1/32 double precision speed. The 460 is Fermi and 1/8 and the 750Ti is Maxwell and 1/32. There are variations with some of the Titan cards and server cards which allow things like 1/2 or 1/3 depending on the generation. The TDP of the 460 is also around 2.5x that of the 750Ti. The 750Ti is only a 60 watt card which is low for a gpu. It is almost as efficient as most of the 900 series gpus(Maxwell gen 2) 

20161106, 20:29  #2544 
"Kieren"
Jul 2011
In My Own Galaxy!
2^{2}×43×59 Posts 
Thanks! I looked at related sources, but obviously not carefully enough. Actually, I think I read the general Wiki on CUDA.
Last fiddled with by kladner on 20161106 at 20:30 
20161107, 05:22  #2545  
"Kieren"
Jul 2011
In My Own Galaxy!
2^{2}×43×59 Posts 
Quote:
Quote:


20161107, 15:42  #2546 
Just call me Henry
"David"
Sep 2007
Cambridge (GMT/BST)
1011010100010_{2} Posts 

20161107, 16:42  #2547 
"David"
Jul 2015
Ohio
205_{16} Posts 
I see this pulled out over and over again about GPUs. "More suited to TF work"
I fail to see how this it backed up by much in terms of actual productivity (exponents cleared  not GhzDays, TF GhzDays are a joke) for many modern cards. I believe the math is "For exponents currently factored < [card specific crossover point], it is better to use your card to TF those exponents. For the giant piles of exponents needing double or first time checks already factored beyond those crossover points, the card is just as productive doing LL work." For most modern cards we are already at or nearly at those crossover points with lots of room to spare, meaning it is equally productive for a person with such a GPU to choose LL from the already factored pile or TF work from the far future list of exponents needing more factoring. It is true that GPUs are far better than CPUs at TF, however we only need enough current generation GPUs doing TF to keep ahead of the CPU/other GPU LL demand pool. What is especially interesting on the AMD side, and somewhat on the NVIDIA side, is that the older generations of cards did 200300 GhzDay/Day of TF, but are close to the same as modern cards at LL work due to 1/2 or 1/3 DP units (4050GhzDay/day). These cards are better suited to DC or LL work than TF compared to a modern card, as in they have a lower cross over point, however even modern cards have crossover points that we often have large reserves of exponents that are factored to that level. My counterargument to continuing to factor far ahead with current or aging GPUs is that it isn't particularly power efficient. By the time we actually need those exponents factored we will likely be 12 generations of GPUs newer, or current highend GPUs will be more accessible and migrated down to be widely in use. To henryzz's point, the direction technology is going does seem to be widening the gap between TF and LL and thus raising the crossover point. That means newer GPUs will likely be just slightly better at LL but perhaps 2x as good at TF. Better to use the GPUs we have now balanced between filling the reserves and checking the exponents and save farfuture TF for the next generation of cards that will be even more efficient at it. 
20161107, 17:17  #2548  
If I May
"Chris Halsall"
Sep 2002
Barbados
22272_{8} Posts 
Quote:
For a while (read: several years) the GPU TF'ing effort was playing catchup. Oliver and Bdot (and NVidia and AMD) completely changed the game with their programs and the respective hardware. Heck, we didn't even initially know how deep the GPU TF'ing should go until James stepped in with his analysis of the TF'ing vs. LL'ing and DC'ing crossover points. This might sound strange coming from the GPU72 guy, but just looking at the Primenet Exponent Status Distribution Map it is clear that the TF'ing is *well* ahead of the LL'ing, DC'ing and even the P1'ing. GPU TF'ing will always be needed, but this is a resource management and optimization problem. As GIMPS' stated goal is to find Mersenne Primes (not factors), perhaps it is time for more GPUs be directed to LL'ing or DC'ing (or Carl's P1 GPU program). But, as always, this is a volunteer effort. Everyone is encouraged to do whatever kind of work rocks their boat. At the end of the day all the work will be needed and useful. 

20161107, 18:28  #2549 
"Kieren"
Jul 2011
In My Own Galaxy!
2^{2}·43·59 Posts 
Thanks to everyone for the discussion and explanations. The GTX 460 may not be very efficient, but it has proven to be rock steady at DC work. I am more leery of CuLu on the 580 because of the odd glitch which affects CC 2.0 cards. I know it's not supposed to spoil the result, but I had more than one proven bad mismatch on that card. That probably means that I did not go far enough in "detuning" it for stability.

20161107, 19:00  #2550  
"Jerry"
Nov 2011
Vancouver, WA
1,123 Posts 
Quote:


20161107, 19:32  #2551 
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2
2429_{16} Posts 
I could use one...

20161107, 19:35  #2552 
"Jerry"
Nov 2011
Vancouver, WA
1,123 Posts 

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