Thinkpads Forum

Justintoxicated wrote: If the 667MHZ ram is only going to run a 533 anyways, would it not be better to get C4 533 rather than C5 667...C4 should be significantly faster than C5 since the ram will not run at 667 anyways?

The Mhz spec for the Ram is just a rule of thumb. They run asynchronously. They have some typical Ras/Cas timing and burst mode speeds, but no fixed clock. If data is ready, it is buffered and transfered via FSB to the CPU. There are a lot of non-deterministics in this whole timing and the actual speed you'll get is pretty difficult to predict beforehand. But as FSB800 is by far slower than 2x533 this Ram usually is fast enough. But for some modes/situations it can show a tad performance deterioration in the range of some percentages. As this anyway will be minor, you could pick the cheapest Ram.

pibach wrote:The Mhz spec for the Ram is just a rule of thumb. They run asynchronously. They have some typical Ras/Cas timing and burst mode speeds, but no fixed clock.

If you are referring to "old" asynchronous DRAM, then that is certainly true. However, today's systems use synchronous DRAM; SDRAM, DDR, DDR2 which does have a master clock on which data access is determined. A memory rated for a certain clock rate (e.g., 533Mhz or 667Mhz) can run at slower or sometimes faster rates, depending upon the setting of CAS latency and other timing parameters.

rkawakami, yes you're right but for non-tech people it might be better to understand that there is no fixed data rate.

And for certain motherboard, chipset and brand combinations, the timing will get into non-deteministics. Thats why some brands have better reputation than others.

pibach wrote:rkawakami, yes you're right but for non-tech people it might be better to understand that there is no fixed data rate.

And for certain motherboard, chipset and brand combinations, the timing will get into non-deteministics. Thats why some brands have better reputation than others.

You can't set the timing Manualy in the bios? (I don't have mine yet and estimated ship date looks like ti will take them an entire MONTH get get the laptop to me).

I know on my current home PC (Reg DDR) I had some OCZ C2 PC3200 as well as some G.Skillz PC3500 or was it 3800 C2.5 or C3

Regardless the G.Skillz when downclocked to PC3200 Speeds was not stable with C2 timings, leaving the OCZ far superior at default MB speeds. However once the MB was overclocked and the FSB was maximized and in sync with the CPU's memory controller the G.Skillz ram did show some improvement as per benchmarking, lower case latency but higher FSB.

On the same note, the C2 OCZ was not stable at any latency above it's rated speed. It really just depends on the chips used.

It used to be that PC3200 C2.5 was the exact same memory as PC3000 C2 way back when. These days that is not necessarily, and unlikely the case.

This is why I would like to know if I should pickup C5 PC 5300/5400 or if I should pickup C4 PC 4200. If the memory is only going to be run at 533 MHZ (in either case and you are all very sure of this?)then the PC 4200 C4 would likely be a safer choice, although some PC5300 or even DDR800 may well be able to run faster case latencys at 533MHZ (I( don't know I have not tried), you could get stuck with memory that will not run C4 when underclocked.

Since I will not be overclocking my laptop, I would just like to get the memory that is gauranteed to run C4 latencies @ 533 MHZ (if that is truely what we are limited to).

Seems to me that the most solid choice would be to purchase PC4200 C4 if all other ram is going to be downclocked to 533 MHZ anyways, this way I can ensure I can use C4 latencies and not get stuck using C5 latencies at 533MHZ?

Hope I just explained my question well enough now to get a solid answer.

Justintoxicated wrote:
Seems to me that the most solid choice would be to purchase PC4200 C4 if all other ram is going to be downclocked to 533 MHZ anyways

No, there isn't anything "downclocked". There is no link between FSB clock and Ram clock, Data from memory controller is transfered asynchronously (even though DDR2 Ram is synchronous). The memory controller of Santa Rosa chipset is specified to handle 533 or 667 Mhz Rams. The faster the better. In principle. If you have integrated graphics (x3100) this also accesses the Ram. But you cannot transfer more than 6,4GB/s (theoretical upper bound) over FSB800 which links the Chipset to the CPU, that's why 667 will not be faster than 533 Rams (as explained there might be a minor difference of some % though).

Well Currently I'm looking at this memory

http://www.newegg.com/Product/Product.a ... 6820211200

Looks like the latencies are 5-5-5-12 rather than the standard 5-5-5-15. (not much difference but the memory is cheaper as well so thats always a plus)

However I can't find any info as to how long the warranty is good for? I think the translation is a bit off so I'm assuming it is lifetime.

http://www.adata.com.tw/adata_en/service_guide.php ?

Well I ended up ordering this memory

http://www.newegg.com/Product/Product.a ... 6820141342

$63 for 4Gb 667 PC5400/5300...It was hard to pass up and was a hell of alot cheaper than Memory from Lenovo for $400 more lol

When are Laptop companies going to learn they are losing money by gouging the customers... PQI had decent reveiws, even for overclocking (although I did not find any reviews on these particular chips). Hope they work (fingers crossed)