I have an FX 8350 a Corsair AX850 a ASUS M5A99FX PRO R2.0. for a long time ive been wanted to overclock via FSB not multiplier. I have an overclock with the multiplier of 4.8GHz. I would like to know how to over clock the FSB. I want to increase the HT Link, NorthBridge frequency.
Well you should have bus speed 200 in bios. So you are increasing bus speed multiplying it with mulitplier. I don't recommend you to go with FSB only. Try mixing both so for 4.8ghz you can set multiplier to x22 and fsb to 218. Under that you can lower your ram speed to around your normal ram speed. Also you can set NB freq to around 2400mhz and HT Link to 2600mhz (it won't be round number cause you increased your FSB by 15 which changes everything). Sorry for my bad English :)
what voltages would I adjust and how would I stress the HT Link and NorthBridge
It depends on whole OC. I have HT & NB freq. both at 2400mhz and NB voltage 1.1V, CPU/NB @ 1.2V, HT @ 1.2V. But don't overvolt your NB cause on Asus boards it gets TOO hot even on idle (try to put a finger on it), my CPU/NB voltage at stock was 1.4v which is imo way too high, so i lowered it to 1.2v and it's still stable after hours of stress testing cause auto voltages tend to overvolt everything from CPU to HT and NB frequency. Now that voltages MAY be enough for you but CPU voltage is what will give you a lot of fun time with finding a sweet spot :D. I would guess for 4.8ghz you will need around 1.5v (maybe a bit less) for good stability - now if you have good water cooling and can stay under 62c on cores and under 71c on cpu socket during stress test you're good to go.
FYI 2600mhz on most AM3+ boards is the limit of any justifiable performance gain. When you go past that, you may take a hit on performance with the CPU since the NB is very sensitive. NB and HT Link should be the same speed, i forget which but one can't go faster than the other. AMD recommends 2600mhz on HT as optimum performance. I Would definitely take a look at the AMD Bulldozer guide done by ASUS, it's very informative on how NB, NB-CPU, and CPU performance are relative to each other and what will benefit performance best for the task you need. those 3 parts benefit certain task in different ways, raw CPU performance won't necessarily perform best for rendering needs as NB performance may. NB-CPU may benefit RAM performance better when overclocking, and etc.
Overclocking the FSB seems to be the most effective way to get a better overall overclock. This means you may need to dial down your CPU overclock to compensate. From my experience, doing slight overclocks at a time will be the best way because of how performance stability changes drastically since you're overclocking EVERYTHING with FSB. On my Gigabyte 990fxa ud3 for example i was able to get the FSB to 250 stable. If you read that guide from ASUS it'l even state how stability drops but the potential of performance gains are much greater.
CPU/NB overclocking can be difficult as you do need to raise CPU/NB voltage and depending on ram speeds and the amount you have installed. You can see here what I have. Tested with IBT stable and over a week gaming and normal usage with no problems without rebooting. Take your time and watch the voltages and heat. I am on a custom loop.
Happy Overclocking.
Damn, that's a damn good overclock, are you running your CPU @ 1.36V? That's nuts for 5Ghz OC.
I wish it was 1.36v. I need 1.608v to run that..it is my daily user. I run this 24/7. The voltage is actually 1.644v because I set LLC to high (so I am working with a little bit of Vdroop). Ultra high was causing to many temperature spikes.
I've been experimenting with using the FSB to OC instead of multiplier and the results are great. It just takes a lot longer to dial in since there are many more factors to consider. Colloquial wisdom from a bunch of different forums says that either a higher HT or having the NB and HT match is best, usually around 2600. I've seen some guys DD up to 2800/3100 on their NB/HT though. The key that I've found is to find the "island of stability". Every motherboard is different, but there are supposed FSB speeds that work better. I usually try and see 230, 240, 250, 260, 280, and 300. My mobo really really like 264 right now, so I'm gonna stick with it and see what I can pull off, but try a myriad of speeds.
Thanks for sharing your overclock, that helps a ton. I'm stuck at 4.9 Ghz right now and I don't have the time to spend hours on testing at the moment. Here's what I'm at right now with the baseclock at 245 Mhz
The difference is I'm not on a custom loop but a 240mm AIO and I have to watch my VRM temps very closely.
