Help me clear up my Athlon64 confusion! :)

I have experience with Athlon XPs, but I am a little confused with my new Athlon64, even after reading about them.

I looked around in my BIOS on my Neo2 Platinum, and I all I managed to do was increase the memory voltage to 2.8 and the CPU FSB to 220. When it POSTed, my memory was running at some odd 170 mhz. I want to run my memory at a little bit over 200 mhz since it was able to do that before with my old Athlon XP, and I would like it to be parallel with the CPU FSB. I have no idea how to do that...

All I could locate for this in the BIOS was some setting that is supposed to adjust the maximum memory speed?

Any help is greatly appreciated!

read the sticky a few times.

Memory is found like this:

Cpu Speed / multi = HTT speed

HTT speed x mem divider = Memory speed

I have a gigabyte board so Im not sure what exact option it is in your bios but mine says something along the lines of:

Max memory clock: 100, 133, 166, 200

200 is 1:1 so memory speed = HTT speed
166 is 4:5 so memory speed = HTT x .8
133 is 2:3 so mem speed = HTT x .6667
and im guessing 100 = HTT x .5

The mobo switched to 5:4 unless you manually set for 200

I read the guide, that's what I said in my first post. I don't understand it, and still don't. Maybe I'm just dumb, but I need some help.

I started to understand your post, but then I did a quick calculation, and I have something wrong.

2000 mhz / 10 =200

max mem speed at 200 should give me a memory speed of 400 DDR, but instead I get 333 DDR. Help help help!

DipStickTony said:

Max memory clock: 100, 133, 166, 200

200 is 1:1 so memory speed = HTT speed
166 is 4:5 so memory speed = HTT x .8
133 is 2:3 so mem speed = HTT x .6667
and im guessing 100 = HTT x .5

Click to expand...

And from your sig it looks like you only have DDR333.

I know.. but look at my calculation and tell me what I'm doing incorrectly:

2000 mhz (Cpu Speed) / 10 (multi) = 200 mhz (HTT speed)

Then, if I set my max memory speed at 200 mhz, my memory should be running at 200 mhz, but it's not.

What timings are you running even? You must have something on auto for it to be resetting itself to 333.

CPU FSB: 200
CPU Ratio: 10
HT: 5x
Max Mem Speed: 200
Mem Timing: 2.5,3,3,7

CPU-Z says the FSBRAM ratio is "CPU/12" if that tells your anything.

As the A64 have their memory controllers on the die, it means that the dividers they now use are a little bit different.
Instead of 1:1, 5:6, 3:5 etc, you now use the CPU : DRAM divider.
So if your CPU multi is x10, and your memory divider is /12, and the HTT is at 200, this is what you do:

200x10 = 2000MHz (CPU speed)
2000/12 = 166MHz (Memory speed)
Now if you want the memory to at the same speed as the HTT, you need the CPU multiplier and the RAM divider be the same number. Like x10 and /10
200x10 = 2000MHz (CPU speed)
200/10 = 200MHz (Memory speed)

From
Overclocking setting for various bus frequencies

hitechjb1 said:

memory_bus_frequency = CPU_frequency / CPU_memory_divider
or
memory_bus_frequency = CPU_multiplier x HTT / CPU_memory_divider
where
CPU_memory_divider = ceiling(CPU_multiplier / memory_HTT_ratio)
where memory_HTT_ratio = 1/1, 1/2, 2/3, 3/4, 4/5, 5/6, 7/8, 9/10, ... (availability of somel settings is bios/motherboard dependent)

Click to expand...

From the above equations:

Case 1:
If CPU_multiplier = 10
memory_HTT_ratio = 1:1 (bios setting)
CPU_memory_divider = ceiling(10 / 1) = 10
CPU_frequency = CPU_multiplier * HTT = 10 * HTT
memory_bus_frequency = CPU_frequency / 10 = HTT

Case 2:
If CPU_multiplier = 10
memory_HTT_ratio = 5:6 or 166 max memclock (bios setting)
CPU_memory_divider = ceiling(10 / (5/6)) = 12
CPU_frequency = CPU_multiplier * HTT = 10 * HTT
memory_bus_frequency = CPU_frequency / 12 = 10 * HTT / 12


Then put in the value of HTT will determine the CPU_frequency and memory_bus_frequency.

In many A64 bios, the term HTT is used interchangeably with FSB.

I have read your stuff, and have tried changing everything I can in the BIOS, but I can't change the memory divider from /12. If I change my CPU speed to 2400, though, it'll be at 200.. That's about all I can do, though.

If your memory is ddr333 and you put the memlock to 200, you'll still be running your ram at 333/166. The memlock on the neo nf3 is an upper limit, not an overclocking method or speed decider. Your ddr333 is going to default to its rated speed, to overclock it you'll have to up the fsb

So in order to get to say 2.6 GHz, I will need to put the CPU speed at 260 (because my multiplier thing won't go higher than 10), and then put the max memory speed thingy at 166? The memory would then be running at

260 x .8 = 208.

Am I right?

EDIT: WHOOPS, girlfriend's account. This is OLMI, hehe.

In most bios, such as for MSI K8N Neo2, there is a setting called memory maxclock. It is defined as the max memory bus frequency relative to the default 200 MHz.

So if
max memoryclock is set to 200 MHz => memory_HTT_ratio = 1/1
max memoryclock is set to 166 MHz => memory_HTT_ratio = 5/6
max memoryclock is set to 133 MHz => memory_HTT_ratio = 2/3
...
regardless of what memory rating is used (whether it can run stable is another story).

For CPU_multiplier = 10,
if memory_HTT_ratio = 1/1, memory_bus_frequency = CPU_frequency / 10
if memory_HTT_ratio = 5/6, memory_bus_frequency = CPU_frequency / 12
if memory_HTT_ratio = 2/3, memory_bus_frequency = CPU_frequency / 15
...
as explained earlier or in the sticky post.

Since HTT is usually set between 200 - 250+ MHz in order to maximize the CPU_frequency to 2000 - 2500+ MHz,
if PC2700 memory modules is used, the memory_HTT_ratio has to be set to 5/6 or even 2/3 in order for the slow memory to have a chance to give a stable system.

E.g.
At CPU_multiplier = x10
HTT = 200 MHz
CPU_frequency = 2000 MHz
memory_HTT_ratio = 5/6
memory_bus_frequency = 2000 / 12 = 167 MHz
If memory_HTT_ratio is set to 1/1, most likely system won't boot or be stable.

At CPU_multiplier = x10
HTT = 240 MHz
CPU_frequency = 2400 MHz
memory_HTT_ratio = 5/6
memory_bus_frequency = 2400 / 12 = 200 MHz (It won't work again, too high for PC2700) <--- SHOULD GET BETTER MEMORY, at least PC3200)

Have to set memory_HTT_ratio = 2/3
memory_divider would then be 15
memory_bus_frequency = 2400 / 15 = 160 MHz (which is within memory spec)


For details,
Overclocking setting for various bus frequencies

Memory bus frequency setting, SYNC/ASYNC mode

I think you mean 4:5 ration. then yeah, if your mobo goes by ratios, then yes it'd be 4:5, if it goes by dividers, you'll want the /12 divider for your RAM.

The Coolest said:

I think you mean 4:5 ration. then yeah, if your mobo goes by ratios, then yes it'd be 4:5, if it goes by dividers, you'll want the /12 divider for your RAM.

Click to expand...

Not, it is not 4/5, it is 5/6.

166:200 = 5:6

166/200 = 5/6

I have seen many posts making such errors.

At 5:6 or 166:200, the memory_divider is 12.

Had it been 4:5, the memory_divider would be 13.

CPU_memory_divider = ceiling(CPU_multiplier / memory_HTT_ratio)

For CPU_multipler = 10, putting in the number, we shall get

At 5:6 or 166:200, the memory_divider is 12.

At 4:5 or 160:200, the memory_divider is 13 (most bios does not support this setting).

The memory_divider calculation and vaious settings can be summarized in this table

Yeah, you're right. My bad. Didn't calculate the multi correctly...

Ok, well then according to what you guys are saying, if my max memory setting is at 200, my CPU ratio is at 10, and my HTT is at 200, my memory should be 2000/10, which would be 200, but it's not. So what's the deal? I saw another thread where someone had to move the memory modules to different DIMM slots, but that didn't fix the problem. It seems to be stuck on a max memory of 166.