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Need help OCing an A8 3870

post #1 of 9
Thread Starter 
I am pretty new to the APU chips and am just trying to understand where their sweet spot is at. What should I turn off in the BIOS, should I just use the multiplier. What is spread spectrum. What is the best HT clock. Should I mess with the GPU clock and so on. Thanks for your input. This is for a computer I am building for a friend, and I would like to give it a nice (mid) overclock, but nothing that is going to give me grief. The specs are here in my build log. I am using a H60 cooler.
post #2 of 9
Unless it's a "K" series unlocked chip. you won't get far and it really won't be worth your time. Much like the Intel APUs, these chips have a base clock which is tied to the PCIE bus, ect, and raising it up much at all can be a headache for most users. Do tune your memory though, as it should help the graphics side of the APU much.
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post #3 of 9
Thread Starter 
Quote:
Originally Posted by damric View Post

Unless it's a "K" series unlocked chip. you won't get far and it really won't be worth your time. Much like the Intel APUs, these chips have a base clock which is tied to the PCIE bus, ect, and raising it up much at all can be a headache for most users. Do tune your memory though, as it should help the graphics side of the APU much.

Yes, its unlocked
post #4 of 9
Quote:
Originally Posted by ericld View Post

Yes, its unlocked

Sweet, just raise the multiplier and adjust voltage as needed. Maybe you can hit near 4GHZ. There is a way to raise the graphics core frequency too, but it's more of a hassle and more for benching.
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post #5 of 9
Your cpu speeds start to get difficult near 3.6 (air) depending on what type of cooling you are using. 1.4ish-1.45v at 3.6 is common for a8's.
GPU speeds for the k series should be adjustable with a multi in the bios as well. Mid 900's I've seen for the k chips on air. check this with a bench to confirm, it doesn't do squat for the locked chips, and rightly so, but its there and should be easy.
The northbridge in these chips can go 900+, my 3850 nb only liked to go to 930-940 with ~1.16-1.17v. Does help performance to get that up to a nice speed, but is also cause of instability easily.
Mem controller can max out your memory + mobo. Mem speeds are going to be done with your baseclock after 1866 (9.33x) and then everything (cpu/gpu/nb) goes up, but not always reported in bios, so be careful with high baseclocks and high nb multis. High mem speeds will get better gpu performance, but semi-high clocks with tighter timings give the cpu an edge.

Baseclock increases cause vga out issues almost immediately, so use digital outs if high mem clocks are wanted.
AHCI/Raid modes crap out really early on baseclock increases as well, so if you are using an ssd and want ahci mode don't bother investing in great memory, cause it will be untapped.

Yeroon
post #6 of 9
Thread Starter 
Quote:
Originally Posted by Yeroon View Post

Your cpu speeds start to get difficult near 3.6 (air) depending on what type of cooling you are using. 1.4ish-1.45v at 3.6 is common for a8's.
GPU speeds for the k series should be adjustable with a multi in the bios as well. Mid 900's I've seen for the k chips on air. check this with a bench to confirm, it doesn't do squat for the locked chips, and rightly so, but its there and should be easy.
The northbridge in these chips can go 900+, my 3850 nb only liked to go to 930-940 with ~1.16-1.17v. Does help performance to get that up to a nice speed, but is also cause of instability easily.
Mem controller can max out your memory + mobo. Mem speeds are going to be done with your baseclock after 1866 (9.33x) and then everything (cpu/gpu/nb) goes up, but not always reported in bios, so be careful with high baseclocks and high nb multis. High mem speeds will get better gpu performance, but semi-high clocks with tighter timings give the cpu an edge.
Baseclock increases cause vga out issues almost immediately, so use digital outs if high mem clocks are wanted.
AHCI/Raid modes crap out really early on baseclock increases as well, so if you are using an ssd and want ahci mode don't bother investing in great memory, cause it will be untapped.
Yeroon

Thanks, that was some good info. This mini iTX board isnt making it easy, but I have it at 3.4 with1.42 stable after a few hours on Prime. Now its time to bump the HT and GFX up a little. What does spread spectrum do and should I disable it for overclocking.
post #7 of 9
Quote:
Originally Posted by ericld View Post

What does spread spectrum do and should I disable it for overclocking.

When enabled the spread spectrum function reduces the EMI generated by your components but it can have some impact on performance by doing so. I always keep that option disabled.
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post #8 of 9
Quote:
Originally Posted by ericld View Post

Thanks, that was some good info. This mini iTX board isnt making it easy, but I have it at 3.4 with1.42 stable after a few hours on Prime. Now its time to bump the HT and GFX up a little. What does spread spectrum do and should I disable it for overclocking.

I am using the asrock a75m-itx, same boat. Small case and 300w ps.. But the scythe big shuriken 2 does a great job of fitting nicely and cooling great with a fan upgrade, the tradeoff was most definitely the install. Had to take my ram heat spreaders off too. Take the whole comp apart to change ram sticks at this point.

I don't have the option for spread spectrum so no idea how useful it is.
post #9 of 9
Thread Starter 
Quote:
Originally Posted by Yeroon View Post

I am using the asrock a75m-itx, same boat. Small case and 300w ps.. But the scythe big shuriken 2 does a great job of fitting nicely and cooling great with a fan upgrade, the tradeoff was most definitely the install. Had to take my ram heat spreaders off too. Take the whole comp apart to change ram sticks at this point.
I don't have the option for spread spectrum so no idea how useful it is.

I put a Corsair H60 on it but even with low profile ram, the water tubing still rubs it.. Just kept the multiplier set for 3.4GHz, bump the voltage and upped the GFX a little.
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