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Question about AMD cpus in general.

Forum CPU & Components : CPUs - Question about AMD cpus in general.

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dmv915   07-02-2009 at 08:39:01 AM

From what I have learned about amd and their cpus is that they each have their own individual clocks the three being the cpu speed, hyper transport, and memory speed all of which revolve around one core clock. My past experiences have revolved around intel p35 and p45 and it was much easier to grasp than with amd. What I learned about intel systems was that it was more efficient to have a fsb:dram frequency of 1:1, which raises my first question.

1. Do amd systems benefit from running 1:1, or is it better to have a higher memory multiplier? I'm assuming it's better to have a higher multi since most phenom IIs have a core clock of 200mhz, but I would like some clarification.

2. This question relates to the first one somewhat. Say you're trying to run ddr2-1000. To reach this speed should you have a higher core clock and lower memory multi or a lower core clock and higher memory multi?

3. Does overclocking hyper transport do anything beneficial?

------------------------------ e8400 @ 4.00 ghz (500x8)
Gigabyte ep45-ud3r
4 GB G.Skill ddr2-1000
Msi 8800 gts 512 oc
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jaydeejohn   07-02-2009 at 09:06:37 AM
- 0 +

Check out this link

http://www.techreaction.net/2009/0 [...] ssentials/

------------------------------ I went drifting, thru the capitols of tin, where men cant walk and cant freely talk, and sons turn their fathers in
 Reply to jaydeejohn
dmv915   07-02-2009 at 09:54:38 AM
- 0 +

So one thing that struck me from these articles is that they both talk about is north bridge overclocking. I'm a little bit confused on this. When they refer to the northbridge clock is it in reference to the frequency of the CPU memory controller and L3 cache or the hyper transport clock?

------------------------------ e8400 @ 4.00 ghz (500x8)
Gigabyte ep45-ud3r
4 GB G.Skill ddr2-1000
Msi 8800 gts 512 oc
Reply to dmv915
buzznut   07-02-2009 at 10:13:52 AM
- 0 +

The northbridge clock can be set independently of the HT speed.

Reply to buzznut
buzznut   07-02-2009 at 10:23:17 AM
- 0 +

The reference clock can be thought of as FSB. this clock is defaulted at 200Mhz. There are then different multipliers for northbridge speed, ram speed, CPU, and HT link.

Reply to buzznut
megamanx00   07-02-2009 at 10:34:47 PM
- 0 +

Since the memory controller is on the CPU die that is the northbridge they are generally talking about (not the one on the motherboard). For older Athlon AM2 CPUs the memory clock is determined by the CPU speed divided by some divider. For an Athlon 5000 with a speed of 2600 MHz, the divider for DDR2 800 was 7 so 2600 divided by 7 results in about 371 MHz (DDR 742MHz), which is a little short of 400MHz (DDR 800). It wasn't until the Phenom that AMD chips decided the memory speed based on the core clock (referred to in the BIOS often as the FSB even though it's not an FSB) and some multiplier.

------------------------------ Playing X-Men Origins: Wolverine Athlon 64 X2 5000+ @3.24 Brisbane | GIGABYTE GA-MA790X-DS4 | 4GB Mushkin DDR2 1066 | Plextor 760A| 2x 3850 512M CF| WD 1TB Black| Fortron Blue Storm II 500W | APEVIA X-Dreamer Black | Win XP Pro & Vista Buisness 32bit
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jaydeejohn   07-03-2009 at 12:04:23 AM
- 0 +

You can bet that bios info will change, now that Intel isnt using the bus anymores either

------------------------------ I went drifting, thru the capitols of tin, where men cant walk and cant freely talk, and sons turn their fathers in
 Reply to jaydeejohn
photonboy   07-03-2009 at 05:33:51 AM
- 0 +

You haven't specified WHY you wish to overclock your CPU.

If it's for games, you should run the Task Manager in the background (CTRL-ALT-DEL) and monitor your CPU to see if it's reaching 100%. If not you are limited by graphics.

This test was easy for single core, but it's slightly more complicated for multi-core. Basically if NO core/thread reaches 100% then you have no reason to overclock your CPU. If one does, it's not certain as it depends on whether the others pick up the slack (how the game is programmed).

I don't recommend overclocking unless you know you have a reason. I overclock my X2-4800+ by 20%.

I first drop down the RAM timings to 166MHz (333MHz dual). I then bring up the CPU timings. If I don't drop the RAM first then my RAM becomes unstable. I'm not being very specific here.

There's lots of info on the net. It depends on the CPU as the architecture keeps changing.

You should just look up your CPU specifically, but again don't do it without a reason.

Reply to photonboy
meodowla   07-03-2009 at 11:17:08 AM
- 0 +

My AMD system works in 1:2

Reply to meodowla
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