A technician friend of mine told me that installing 2 x 2GB in the T60p can trigger memory parity errors...that 3 GB should be installed.

Is this true?

Thanks

from what I know on this topic is that the T60has 32 bit os and 32 bit does not support 4gb of memory even if installed.

Your best bet in my estimation is to use 1gb + 2gb. I have heard of errors, also you wont't be utilizing the extra 1gb of memory.

You're right that the T60p 32 Bit only recognizes 3GB, but some people install 2 x 2 GB anyway. But it's interesting if the installation of the additional 1 GB unutilisable RAM could trigger a parity error.

Thanks

That's a load of BS.
Installing 2+2GB will make the RAM run in Dual Channel mode, ca. 5% faster than the same type RAM in 2+1GB, which would run in Single Channel mode.
That only 3GB is 'seen' is a well known fact and a hardware limitation of the T60.

The real-world performance boost of symmetric mode vs asymmetric mode is negligible for most users, usually somewhere around 0-8% increase.

Avoid parity errors and do 2+1GB

Any tangible proof?

Do you want me to reproduce one? Or link you to countless examples?

hello beast....

a few examples would be nice to see..

AND, welcome to the forum..

Thanks, it's been a great 24 hours, not contentious at all...

Intel 945 Chipset that is in the T60s is not capable of addressing more than 3GB. While the same 945 in Dell's and HP's can detect it. This isn't a chipset vs memory issue it's due to BIOS or an embedded controller in IBM's.

Moreover, to say that using 2X2GB in order to achieve dual-channel is silly. Most all modern chipsets and even that of the T60 will put 1+2GB into asynchronous dual-channel. Worst case scenario you are running single channel and receive a negligible amount of performance.

I'm making a video of using 2X2GB sticks in this T60 that I have vs 1+2GB. It's not a consistent issue but the ONLY time I have ever duplicated a Parity Error significantly, is by putting 4GB on the 945 T60's. Not T61.

Again, for the consideration of the OP using 2X2GB is of no benefit on the T60.

This has been discussed a lot and there are various misconceptions here. I don't mind repeating myself and others from time to time, so here goes:

First, I'd like to point out that it _is_ a chipset issue. The 32bit memory controller in the Mobile 945 chipset is only capable of addressing 4GB. Since some of this space has to be reserved for peripheral devices, the usable physical memory will always be <4GB, no matter which vendor's machine you are using.

You said it yourself "the same 945 in DELLs and HPs can detect it". Detect does not necessarily mean "use". The T60 BIOS will also detect 4GB, IIRC, but the operating system will only be able to use 3GB.

Why exactly 3GB? That's a choice made by Lenovo. According to Intel's spec, it is the responsibility of the BIOS to configure the maximum RAM address below 4GB that is mapped to physical RAM. The rest (above it) is mapped to PCI devices. Since there are various system configurations, with different PCI devices, which may require different sizes of mapped address spaces, Lenovo chose to set this limit at 3GB to make sure that under no reasonable configuration the reserved address space will be insufficient.

I'd like to say here that I have no idea where the limit lies for other laptops using the Mobile 945 chipset.

There have been somewhat successful attempts to provide modified BIOSes for the relevant Lenovo systems, which raise the limit to 3.25 or 3.5GB. A full 4GB is not possible, and the more you raise it, the more you are likely to run into problems of being unable to allocate address spaces for PCI devices. In the end, most people concluded that the extra 256/512MB of RAM is not really adding this much performance gain to be worth the trouble.

Thanks for the very lucid and definitive explanation, dr_st.

Thanks Dr_St, it's more or less what I was trying to say, I've come to a lot of my own conclusions on these things, thanks for putting it down clearly.

Thanks, Beastcloud, for your explanation as well, which additionally touched on other issues.

2GB+1GB = Asymmetric Dual Channel Mode (the same applies to any configuration where the DIMM sizes are not the same)

2GB+2GB = Symmetric Dual Channel Mode

2GB+empty slot = no Dual Channel Mode.

So, this guy after being called on spewing BS (by Bill no less), makes a snide remark about the forum being "contentious", then promises video proof for something specious... and never delivers. Classy guy.

So, what's the deal? Will putting 2x2gb into the T60/p cause parity errors? I bought 2x2GB (because at the end of the day, I can sell my previous 2x1GB sticks for enough that it wasn't worth buying only one stick), and one of them died like right away. Clearly, it was DOA, but now I want to know. Is 1GB+2GB definitively better than 2x2GB in my T60p? Am I going to get parity errors with 4GB installed? Where did this idea come from? Can someone corroborate?

B S

plain and simple.

Alright, thanks!

Well, never heard about parity error when using 2x2GB; I've been using 2x2GB in my T60 for around 3 years now and never had any issues.