ram for santa rosa

Hi again,

I'm currently looking at the asus s96s but either way it'll be santa rosa. With an 800 mhz fsb thats really 200 mhz quad pumped, right? Because up until now I've been looking at ddr2 sodimm 667 ram but that would just bottleneck right? Why do they even make that not notebooks? I can't find a good ddr2 400 s gig kit so I guess I'll go ddr2 533. Seems pointless to waste the speed...

Correct?

 

Maybe I misunderstood... but why would ddr2 667 bottleneck on santa rosa? ddr2 667 is the maximum speed santa rosa supports. All the current high end santa rosa laptops use ddr2 667.

Your system would not be living up to its potential if you go with ddr2 533. And ram prices are pretty low right now so you wouldn't be saving much by going with the slower ram. You might save like 5-10 bucks.

 

As mentioned, Santa Rosa can't take advantage of 800mhz RAM modules, it'll downclock to 667mhz. Just pick up sticks of PC5300 DDR2 667mhz SoDimms, and you'll be fine.

 

well thats not really my question/point... a desktop mobo might support up to ddr2 1066, but if your fsb is 400 (a nice oc from the standard 266 and new 333), then anything more than ddr2 800 is pointless, a bottleneck. if the santa rosa's have an fsb of 200, 667 is a huge bottleneck. 400 is exactly whats needed. Unless you can oc a notebook, which I'm not all that ineterested in.

Note that on intel's site all the core's support up to 667. doesnt mean it takes advantage of it.

Any benchmarks to prove this true or false?

 

Santa Rosa can be bottlenecked by 667 MHz RAM. This only occus when a notebook's RAM is not run in dual channel. Dual channel is important for Santa Rosa, because if only one module with a frequency of 667 MHz wased used, then it would bottleneck the system under applications which are both processor and memory intensive. Dual channel avoids this bottleneck, because it effectively doubles the bandwidth, and allows the processor to work the fastest, because it is now getting enough data from the increased bandwidth.

 

yes ill be running dual channel. i still dont see how fsb doesnt affect notebook ram. it would be silly to buy dr2 1066 for my desktop if i am only coing fsb to 400, thats 266 of wasted speed.

but anyhoo, what about ddr2 533 having lower cas latency? 533 runs at 4-4-4-12 timings and 667 runs at 5 (assuming to be 5-5-5-15 or something). Which is more important for performance, clock speed or latency?

I still dont see how 667 mhz ram doesnt bottleneck, even in dual channel, on a 200 fsb.

 

I'll give you an example. Say, a notebook has a processor which has an 800 MHz FSB. That means for the processor to be working at full tilt, it needs a data throughput of 6.4 GB/s. Any slower than that, will mean the processor is being bottlenecked. So, by that definition, the RAM used in the notebook would also need to be 6.4 GB/s, which means its has to be 800 MHz RAM. Currently, that is incompatible with Santa Rosa.

An alternative is to use 667 MHz RAM in dual channel. One its own, one module of 667 MHz RAM will provide 5.3 GB/s of data bandwitdth. However, when two modules of 667 MHz are run in duall channel, it will provide twice that: 10.4 GB/s. This is more than enough to feed the processor, which does not result in any bottleneck. I hope this makes it a little more clearer now.

CAS latency is something an average user shouldn't worry about. Users who run memory intensive applications, where the memory is accessed many times, need to look into RAM with lower latencies. f you do want faster RAM, then there are 667 MHz RAM modules available with a CAS latency of 4. Both latecy and frequency are important for performance, but generally either 533 MHz or 667 MHz RAM will be fine for almost all applications.

 

So what would be better, 3gb 667 or 2gb dual channel(1334)?

 

Both of those will run in dual channel. So for applications which are not memory intensive, either will do fine. For applications which require alot of RAM, then the 3 GB option will be better.

 

Thanks, how can 3gb run in dual channel with a 2gb and 1gb stick?

 

Newer Intel chipsets and the previous Intel 945 chipset can run different density modules in something known as asymmetric dual channel. Its not quite the same as dual channel, but it still provides a bandwidth increase. The 2 GB you mentioned, will run in "true" dual channel, known as symmetric dual channel.

 

so any 1gb and 2gb module so long as they are both 5300 (677) will run in asymmetric dual channel, providing 800?

Many Thanks Zero

Batch

 

Most modules with different densities will run in asymmetric dual channel, however, some may not. Its generally better to try and get modules from the same manufacturer, as this increases the likelyhood of modues in working in dual channel.

 

How about getting two 2gb sticks would that make them run in asymmetric dual channel?