X61s thinkpad PC2-5300s vs. PC2-6300s compatibility issue

[sphinx0101]

Hi All,
I am very new to this forum. I bought my X61s thinkpad a year back. Extremely happy with it. It came with 2 GB ram (two 1GB sticks) and recently I wanted to upgrade my ram. I ran the Crucial compatibility app. from their website and got a 2 GB PC2-6300s stick. When I was about to install it in my laptop I noticed the existing sticks are PC2-5300s. I have installed the 6300s and noticing better performance although I know that it's backward compatible with the other 1GB 5300s. I didn't do much homework before buying this (I guess I should have checked what's in there). Now I went to the Lenovo website and saw that the default ram suggested by them for the X61s is PC2-5300s. So is there anything to worry about since I have installed a PC2-6300s?

[rkawakami]

Welcome to thinkpads.com!

The PC2-6300 (or PC2-6400, which is the "standard" speed) module will operate at the slower system speed of PC2-5300. The better performance you are seeing is due more to the extra amount of memory you've added than the speed of the module.

[sphinx0101]

Welcome to thinkpads.com!

The PC2-6300 (or PC2-6400, which is the "standard" speed) module will operate at the slower system speed of PC2-5300. The better performance you are seeing is due more to the extra amount of memory you've added than the speed of the module.

Thanks you so much for the quick reponse. My worry was since the default spec in the lenovo website for the X61s is a PC2-5300s, so that doesn't mean that a PC2-6300s cannot be used with the X61s?

[rkawakami]

<snip>... so that doesn't mean that a PC2-6300s cannot be used with the X61s?

Hmmm.... a double negative semantical query... Let me put it like this: The system spec of PC2-5300 means that the memory must be at least capable of running at that speed. As far as I know, the timing system of the memory bus inside the X61 is fixed to run at that speed and cannot be changed, unlike most desktop computers where you can play with the memory timing in the BIOS. Therefore, a slower memory module (e.g., PC2-4200) will not work. Either the BIOS will recognize that the module is of the wrong type (using information inside a small memory on the module called the SPD) or the laptop will function erratically (blue screens, lockups, etc.). 999 times out of 1000, a memory that's rated at a faster timing spec then the computer it's going in will work as it will be running at the slower speed of the computer's timing system. Think of it this way: it's like driving a car that is capable of 150MPH but the throttle been limited to only go 1/2 way to the floor (the computer's speed is holding back the module's potential). What about the 1 in a 1000 times it doesn't work? That's usually due to a setting inside the SPD where it's telling the computer's BIOS that it can't support whatever timing specs the computer says it uses. It's a fairly rare occurrence but it can happen.

ref: http://en.wikipedia.org/wiki/DDR2_SDRAM

edit: I should also say that anytime that you change the memory system inside your computer, you should verify that it works by running a memory diagnostic program. One easy (and free) program is memtest86+. You can get a copy here: http://www.memtest.org/#downiso

[sphinx0101]

Great info Ray!!!!!!! Thanks once again. 1 in a 1000 times failure rate is a relief. So what would you suggest - if possible get the PC2-6300s exchanged for a PC2-5300s from Crucial? I got my laptop with Vista Home when I bought it. Used detailed info posted on notebookforum.com to downgrade to XP the day it came. Everything running smoothly so far (touch wood!!) with a few occurrences of blue screen once a while. Now giving a thought of upgrading to Windows7 in a month or so. Do you know any issues I might be facing with Win7 due to such incompatibility if I plan to keep the PC2-6300s? And also if I plan to upgrade the remaining 1GB stick to a 2 GB sometime later this year then I might face the same dilemma - whether to choose PC2-5300s (as per computer capability) or PC2-6300s (as per matching with my current 2 GB stick). Any suggestion will be appreciated.
Sorry to bother you with so many questions, it's just that I love my thinkpad so much, I just want it to give the best treatment.

And also I am a graduate student running lots of processes simultaneously......7 to 8 pdf files, statistical software (SAS) and typesetting software (Latex). So I do care about optimal performance as well.

[IvanAndreevich]

There is no need to downgrade your RAM - it should be fully backwards compatible. Therefore, choose whichever is available and cheaper.

Also, BSOD is definitely not normal operation. You need to run memtest, as specified above.

Win 7 install and runs very well on X61 machines. No driver issues at all.

[sphinx0101]

Hey Ivan, thanks for the info! That clarifies a lot of things. Can't wait to load the thinkpad with Win7

Do you know if there is a post in this forum for step by step clean install of Win7? As I said before, my thinkpad came with Vista home which I wiped out to install XP pro and I remember to do some changes in the BIOS to make the XP cd bootable. So I was wondering whether I need to make any BIOS changes once again for a fresh install of Win7. Anyways this is not the proper thread to discuss this issue, so I will go ahead and search the forum. But in case you know there is a thread discussing that lemme know. Thanks once again for the help!

[IvanAndreevich]

Actually, no it's pretty much straightforward - boot from the DVD, and install. Nothing unusual is required, everything works right out of the box.