Bf4 Bottlenecking i5 750 @2.66ghz and a Sapphire Hd 7970 3gb

everything looks good to me, the only thing that could possibly be effecting anything would be that your processor is at a very low clock speed. but i wouldnt see that being a problem because as long as you have a quad core processor it shouldnt bottleneck anything (unless its a very high end card) because games mostly depend on your gpu. I dont know maybe something on your card died, run some benchmarks to make sure all your hardware is running properly.

I would guess that the old i5 is holding you back. Especially with its low clock and outdated architecture. Why not OC that sucker a bit? Also what non descript 660w psu do you have? Not that it would effect the performance but it just sounds sketchy. BF4 is pretty demanding, have you run FRAPs to see what kind of frames you are getting? Look at a benchmark for the 7970 and compare...

Here is a link to Fraps:

http://www.fraps.com/download.php

Below is a link that shows a 7970 ghz edition and a 7950 so you can get the idea of what performance should be at 1080p from a non-bottlenecked system and compare.

http://www.bit-tech.net/hardware/graphics/2013/11/27/battlefield-4-performance-analysis/3

Had one of those i5s, gave it to my brother.
Mistake.
True, I've now got a shiny i5 4690K/GTX970 rig to play with but realistically the old i5 750/HD7950 is still perfectly fine at 1080 rez, it's main issue was, as has been said, it's low clockspeed so...
SAY GOOD BYE TO THOSE PESKY BOTTLENECK ISSUES!
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Sorry, don't know what came over me there.
Seriously, I did add a Hyper 212 to my own i5 750/HD7950 rig and the results were very good in the CPU intensive games I tend to play like FC3, Metro 2033/LL, even the 'X' space games pepped up a lot (ancient single threaded game engine).
Overclocking isn't for everyone, I know, but research only costs time, and it could easily save you quite a bundle, something I think you'll be very happy about at this expensive time of year.

based off of multiple sources (and personal experience), you need at least 4 cores to run demanding 3d games like bf4 smoothly.

^Agreed. the 2 i3-4150 cores are indeed stronger then a first gen i5 but some games need 4 cores. Battlefield is one of them.

Yeah BF4 looks well optimized for a variety of CPUs, look at the i7 920 with its low clocks..

^No need for clarification I completely understand that. Aside from AMD vs Intel, in most cases however the clock frequency will effect the overall throughput. I'm talking about an intel vs an intel of the same gen.

Guess I'm wrong, sorry my bad.

And back to the actual thread and it's question?
It's no big surprise a more modern CPU is faster and more efficient, but to use one the OP will need to swap MB,CPU and RAM, at which point the HD7970 could easily become another bottleneck, particularly if he opts for something as massively powerful as an i5 4670K/4690K.
Right now his system is fairly well balanced, and still VERY capable, maybe it's not up to current high end standards but it's still more than able to play current games. Even without its overclock my own i5 750/HD7950 could play heavy games like FC3/Metro2033/Metro LL at high settings smoothly, and, obviously, somewhat better when the two parts were overclocked from 2.66/800 to 3.4/950.
@ Mantis2334: Give it an overclock and see how things pan out, mate, you could save yourself several hundred dollars and even if it doesn't work out, you can always swap the cooler into the upgrade.

Yeah give it an overclock and do some measuring with FRAPs or other programs, compare to other 7970 benchmarks and see where you stand.

there is variations on this but the CPU does the donkey work, it handles physics calculations (including particle effects like smoke or water), AI calculations and produces the raw scene data that will be used by the graphics card (think of it as an artists sketch that contains all the objects and lighting info required to produce the final work). This sketch is then passed on (over the PCI-E connections) to the graphics card. The graphics card then paints (renders) the final scene applying various effects as required, passing this finished image on to the display circuitry when it's done.
Because the raw scene data is produced mathematically, screen resolution has little effect on the CPU workload, increasing the number of objects, adding complex particle effects or using high resolution (high polygon) models does.
Because the graphics card can only render a set number of pixels per second, changing the screen resolution has a large effect on its workload as does adding complex effects-lighting, particles and anti aliasing are particularly demanding.
In an ideal system the GPU will finish its render at the same time as the CPU is ready to pass its data to the GPU, so neither is waiting for the other.
If you were seeing: CPU 20%, RAM 70% and GPU 100% it would show a severe GPU bottleneck, because its running flat out and yet the CPU is only 20% used. If you were seeing CPU100%, RAM 70% and GPU 20% the reverse would be true, now the CPU cannot provide enough data to keep the GPU running at full capacity and now there's a severe CPU bottleneck.
The numbers you're seeing suggest a SMALL GPU restriction.

OK, missed the 'Iona GL8E' bit in your first post.
That MB is a Hewlett Packard OEM 'board, so it's more than likely overclocking options are disabled, which will obviously rule that out, no harm in checking though, just hold the relevant key during bootup and check the available options in the BIOS screen.
Here's a link on overclocking the i5 750 to get you started: http://www.bit-tech.net/hardware/cpus/2009/09/21/overclocking-intel-s-core-i5-750/1
Not up to speed on Mantle but from what I've seen your system is performing pretty normally, Mantle gives its boost with low end hardware, something your system lacks.
Maybe updating the AMD drivers will provide a positive change with Mantle, but the frame rates you're getting are pretty typical of systems with your specs.
I'll guess you already know this but I'll mention it anyway: AMD cards don't like Anti aliasing, keep it low, or preferably off for a large frame rate increase.

I suggest you lay off the overclocking, even if it's possible with the current motherboard. Acbel don't make very good units and I suspect your system is already pushing it quite hard-most cheap units don't produce their claimed output and more than a few will fail, sometimes with expensive consequences, at or below 75% of their claimed output. If you're going to change anything in this current build, give it a decent PSU first.

Means that you might want to give the graphics card a little overclock, (CPU at 70%, means it's probably waiting for the GPU to catch up) just don't do it on the current PSU, though.
Shame about the locked motherboard options, that i5 750 is capable of so much more but finding a replacement MB will probably be difficult, that particular design (LGA1156) was very short lived and even used parts on E-bay are rare and can be expensive.

^Right, its not worth dumping any more money into that platform. I would put the money towards a Haswell setup if anything. For the moment you have a perfectly fine rig as it stands.

You're welcome!! Have a nice weekend!