RAM Latency vs FSB Freq question

[Zerohm]

I'm planning on overclocking an AMD 3000+ Venice and I've read not to change the RAM ratio. (Nor do I want to buy 500 MHz RAM)

What latency ratings should I look for and what type of FSB frequency and latency settings can I expect to get away with?

Suggestions?

 

[Zerohm]

I'm only bumping this because I completely changed the question.

 

[Zim]

You can see from my sig that I'm running my ram at 222MHz 1:1. I started off running it at 200MHz 9:10 (=222) and had no problems. I have also tried CAS 2 and CAS 3 as well as 1T and 2T, taking memory benchmarks at each point. Overall my memory performance varied by up to 20%, but I'd bet that the real world effect was neglible. As most people will tell you, CPU speed is king.

Bottom line: get what you can afford and no more.

 

[orangat]

For AMD latency gives better performance improvements. Even the X2 benchmarks don't show a big jump with high bandwidth RAM although it benefited more compared to single cores. Bottom line, get cas 2.5 or faster.

 

[Hacp]

Get ram that has headroom of around 220FBS. This will help you ALOT because that will allow you to get as close as possible to your maximum stable overclock. Without headroom, and being stuck at 200, you will lose performance becuase you might be able to squeeze and extra 50 mHz with ram dividers and varying fsb.

 

[charloscarlies]

Originally posted by: Zerohm
I'm planning on overclocking an AMD 3000+ Venice and I've read not to change the RAM ratio. (Nor do I want to buy 500 MHz RAM)

How are so many people missing this? You absolutely can use ram dividers. It does not hurt performance very much at all.

 

[Zerohm]

Originally posted by: orangat
For AMD latency gives better performance improvements. Even the X2 benchmarks don't show a big jump with high bandwidth RAM although it benefited more compared to single cores. Bottom line, get cas 2.5 or faster.

Orangat,
So basically, out of the three main things to adjust (latency, HTT, multiplier), first set the latency to about rated settings first, then crank up the HTT as high as the RAM can handle. Finally, crank up the multiplier as much as the CPU can handle? (and by "handle" I mean run stable with an acceptable amount of stress on the hardware)

 

[1Dark1Sharigan1]

Originally posted by: Zerohm
So basically, out of the three main things to adjust (latency, HTT, multiplier), first set the latency to about rated settings first, then crank up the HTT as high as the RAM can handle. Finally, crank up the multiplier as much as the CPU can handle? (and by "handle" I mean run stable with an acceptable amount of stress on the hardware)

That's basically correct.

As for bandwidth vs. latency, if you have ram that can run at CAS2.5 with 300 Mhz and above, your RAM will begin to perform significantly better than say 200-220 Mhz at 2-2-2-5 . . . even if you have to use 2T.

My RAM @ 315Mhz (highest stable) and 2.5-4-4-7 2T easily beats my RAM running @ 215Mhz 2-2-2-7 1T (highest stable at lowest timings) and even my RAM @ 250Mhz 2.5-3-3-7 1T

If you have TCCD, running 300Mhz at 1T and CAS2.5 will absolutely crush ~200Mhz CAS2

 

[Zerohm]

Originally posted by: 1Dark1Sharigan1
...
My RAM @ 315Mhz (highest stable) and 2.5-4-4-7 2T easily beats my RAM running @ 215Mhz 2-2-2-7 1T (highest stable at lowest timings) and even my RAM @ 250Mhz 2.5-3-3-7 1T

If you have TCCD, running 300Mhz at 1T and CAS2.5 will absolutely crush ~200Mhz CAS2

Dark,
When you say your RAM @ 315 MHz easily beats X, is that in RAM bandwidth or actual fps? I ask because to run the HTT at 315 MHz, you reduced the fsb multiplex to 3x thus making your fsb 945 MHz, right? I assume the benefits of running RAM at 315 MHz far exceed the 55 MHz loss on the fsb, even if you have to use a RAM ratio less than 1:1, but what effect does that have?

 

[Bull Dog]

Originally posted by: Bull Dog

Originally posted by: thecoolnessrune
Option 2 for sure. If you want a 1:1 divider, then sell your old memory and get some OCZ Gold Edition 2GB Kit. You'll run 4 Mhz slower but that will let you run 1:1. Even if you didn't get more memory, Option 2 is the best way to go.

I'm sorry but this *REALLY* bugs me. Let me make this real clear.

There is no such thing as running your memory at 1:1 timings with A64's
You memory is ALWAYS running A-sync.

Ram speed is baised off of a divider of the CPU speed.

My understanding outlined below.
A 3500+ runs at 2200Mhz.
The base HTT (hyper transport) speed is 200mhz and the bus runs a 5x multi on top of that, so one gets 1000mhz for the final HTT speed.

The CPU speed is also based on the base HTT speed. The 3500+ runs at 200x11 or 2200mhz.

The Ram speed is based on the speed of the CPU not the speed of the HTT bus. In the case of the 3500+, that translates to 2200/11 = 200mhz.

Now lets say you lowered the multiplier of the CPU to 10.5x The CPU would now be running at 2100mhz. Since the on-die memory controller doesn't support half multipliers you'll keep using the 11x divider 2100/11 = 190.9 mhz

Do you see how the only relationship seeming to be 1:1 is the fact that @ stock speeds the CPU and Memory use the same multi/divider?

1800/09 = 200mhz
2000/10 = 200mhz
2200/11 = 200mhz
2400/12 = 200mhz
2600/13 = 200mhz
2800/14 = 200mhz

 

[Zerohm]

Bull dog,
Thank you for interjecting my thread with what really bugs you, bold stuff, and quotes from other threads. Next time I will read up on my A64 terminology. If this *REALLY* bugs you, you are too stressed out man.

But seriously, I understand that A64 runs RAM asyncronously and that ratios are an indicator of the divider settings, not vice versa, but if someone said to you they were running their AMD @ 250x10 1:1, you would know what they were talking about.

I have the equation to calculate A-sync RAM speed, and soon I might understand it 🙂

 

[Bull Dog]

Originally posted by: Bull Dog

Originally posted by: Bull Dog

Originally posted by: thecoolnessrune
Option 2 for sure. If you want a 1:1 divider, then sell your old memory and get some OCZ Gold Edition 2GB Kit. You'll run 4 Mhz slower but that will let you run 1:1. Even if you didn't get more memory, Option 2 is the best way to go.

I'm sorry but this *REALLY* bugs me. Let me make this real clear.

There is no such thing as running your memory at 1:1 timings with A64's
You memory is ALWAYS running A-sync.

Ram speed is baised off of a divider of the CPU speed.

My understanding outlined below.
A 3500+ runs at 2200Mhz.
The base HTT (hyper transport) speed is 200mhz and the bus runs a 5x multi on top of that, so one gets 1000mhz for the final HTT speed.

The CPU speed is also based on the base HTT speed. The 3500+ runs at 200x11 or 2200mhz.

The Ram speed is based on the speed of the CPU not the speed of the HTT bus. In the case of the 3500+, that translates to 2200/11 = 200mhz.

Now lets say you lowered the multiplier of the CPU to 10.5x The CPU would now be running at 2100mhz. Since the on-die memory controller doesn't support half multipliers you'll keep using the 11x divider 2100/11 = 190.9 mhz

Do you see how the only relationship seeming to be 1:1 is the fact that @ stock speeds the CPU and Memory use the same multi/divider?

1800/09 = 200mhz
2000/10 = 200mhz
2200/11 = 200mhz
2400/12 = 200mhz
2600/13 = 200mhz
2800/14 = 200mhz