Now my X41 RAM is Dual Channel, but....

[dmanresa]

My X41 is 512MB. I decided to buy another 512MB (instead of a 2GB) to use the i915PM/GM chipset to do Dual Channel . I supposed that I would have dual speed . But as can be seen in the pictures, the performance only increased 10%.

1062MB/S in Single Channel (64 Bits)
1169MB/S in Dual Channel (Interleaved)

The module I bought was a IBM 512 MB DDR2 533 SO-DIMM FRU:73P3842, the one recomended by Lenovo for the X41.

Does anybody know why I cannot get more performance? Does it have to do with the 99Mhz FSB? I did the same with a workstation with 800Mhz FSB and the memory speed was almost the double!






Thanks in advance.

[comptiger5000]

Probably the low FSB. It can't get data in/out of the CPU fast enough to fully take advantage of the extra RAM bandwidth.

[aaa]

Does it have to do with the 99Mhz FSB?

Yes. 100x4 gives only 400mhz throughput for the fsb, so it can't take full advantage of the dual channel.

You're not missing out on much though, the 10% you see there translate to even less actual increases in performance. As in, the doubled numbers you saw on your desktop probably only made a 10% difference in actual things.

[dmanresa]

As in, the doubled numbers you saw on your desktop probably only made a 10% difference in actual things.

Yes, I have read something like that in the wikipedia. The performance will depend on the type of application. With my Desktop, I work with very hard working memory hungry algorithms, so the speed was the double.

I agree with the FSB throughput. It seems like the memory modules have bandwith enough for that narrow FSB, so there is no need for dual channel.

[loyukfai]

Newer chipsets can utilize dual channel even if the capacity of the 2 modules is not the same, I'm not sure if the one in X41 is capable or not through.

BTW. 10% performance gain in synthetic benchmark is about right as far as I can remember.

Cheers.

[weepy]

I have 512MB + 2GB modules in my tablet. I bought 2GB because of price and because I foresaw this behavior. Some programs report dual channel operation with these modules, I got slight throughput increase, too (I believe it is because graphics uses the 512MB module - not all of it - and 2GB RAM is the other module).

So I think we can conclude that there is no point in buying other than 2GB RAM upgrade for X41, since the dual channel advantage is not here for 2x512MB modules.

[dr_st]

So, indeed the chipset can utilize dual channel with different-sized modules. It's called asymmetric dual channel.

Performance increase with asymmetric dual channel is slightly less than with symmetric dual channel, but even with symmetric it is hardly anything over 5%. Even the 10% is surprising, and would probably not show in anything other than direct memory benchmarks.