September 28th, 2004, 02:14 PM #1
IBM T-41 laptop ||| can I mix PC2100 with PC2700 memory?
I have an IBM T-41 Thinkpad that uses PC2700 memory...
My T-41 has one 512MB PC2700 module in it now. I have an extra 512MB memory module that is PC2100...what are the consequences of running it with that PC2700 memory?
I tested it on another T-41 laptop and there were no issues...it ran fine...the memory was recognized and there were no stability issues.
Before I put it into my own laptop...does anyone know if this could damage the laptop? Damage the memory? Both? Is this the equivelant of overclocking the memory...or is the other PC2700 module automatically underclocked to PC2100 or vice versa?
September 28th, 2004, 02:25 PM #2
The faster memory will clock down to the speed of the slowest memory stick.
It will not harm your system.
September 28th, 2004, 04:59 PM #3
thanks Jarhed -
OK - so then what would yield the best performance for things like Photoshop and Flash? 1 Gig of ram at PC2100 speed or 512MB ram at PC2700 speed?
September 28th, 2004, 05:05 PM #4
September 28th, 2004, 05:51 PM #5
September 28th, 2004, 05:55 PM #6Originally Posted by Jarhed7276
You make it sound like the PC2100 would then slow down to the PC1600 speed.This signature intentionally left blank.
September 28th, 2004, 06:04 PM #7
Doesn't PC2100 run at 266MHz and PC2700 run at 333MHz? The bus speed of the laptop is 400MHz - so...not sure I understand...will the PC2700 now run at PC2100 speeds?
September 28th, 2004, 06:27 PM #8
Thanks Rick I worded that poorly.
For further clarification, though, are you saying that if the FSB is 800 and you have one stick of PC3200 and one stick of PC2100 that the PC3200 stick will run at 800 MHz and the PC2100 stick will run at 533MHz? They do not synchronize?
September 29th, 2004, 10:46 PM #9
The FSB is optional --within the limits set by the chipset and BIOS. But the memory is largely a property of the quaLITYU OF THE Module. and the chips on it.
Some modules I understand are under-rated to maintain prices within market niches. So thier performance I gather is a property of thier intrinsic quality --and the conditions (i.e. voltage) they are placed in.
Correct so far or NO ?
I was tought that memory raelly had the drivers seat up to the pont of FSB and memory is ideosyncratic.
Getting back, If a lappy has a PC2100 RAM and you wish to add--but prefer to pay the small x-tra $$difference for a PC2700 with an eye toward a future update of the PC2100 module, that the machine would run at the speed of the lower module --unless the FSB was set higher and the module was of better than rated quality.
Otherwise, the better Module would slow down to accomodate the slower one.
Interestung subject .but needs clartifications on the various parameters.
.Clarifications are always on Thread !
Keep talking, Evil Rick, and Folkes !
September 29th, 2004, 10:53 PM #10
P.S. If FSB is 333 and one Module is 2100 (266) and the other was PC2700(333), would the PC2100 run hotter than the PC2700?
If it wasn't able to run at FSB333, would the FSB slow down for both Modules ?
Would it (FSB) reach some midpoint, or revert to a lower setting, one that both could handle --say 266, forcing both modules down with it???
September 30th, 2004, 02:39 AM #11
That's a good question - anyone got an answer?
My FSB is 400MHz,
The memory that is supposed to be in it is PC2700 or 333MHz, right?
I just happen to have an extra chip, but it's PC2100 or 266MHz...
So...the FSB is running at 400MHz, the memory is running at 333MHz...now if I add in this slower PC2100 memory, the FSB will stay the same at 400MHz, but will the PC2100 memory have to run at 333MHz and risk overheating...or will the currently installed PC2700 memory drop from 333MHz down to 266MHz to accomodate the slower memory? I am guessing the FSB stays the same at 400MHz no matter what. I don't suppose they'd run at independent speeds would they? They do install in 2 completely different areas in the laptop...so it's not like a desktop where the DIMMS are side-by-side...one dimm is under the keyboard...the other is closer to the front of the laptop but on the bottom...
Remember, this is a laptop and I have no BIOS controls over any of these speeds.
Last edited by rastorize; September 30th, 2004 at 02:45 AM.
September 30th, 2004, 04:48 AM #12
For a 400 FSB cpu the memory that runs at the same speed would be PC1600.
Since we are talking about DDR memory (double data rate, it transfers data at both the top and bottom of the cpu cycle) PC2700 will run at 666 MHz and PC2100 will run at 533 MHz. Both sticks will operate at the speed of the FSB (400 MHz). There is no risk of overheating the memory as they are both operating lower than their rated capacity.
October 6th, 2004, 06:30 AM #13
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There are two parameters that affect memory speed. One is the FSB and the other is the CPU/Memory ratio, usually adjustable in the BIOS.
Memory speed is calculated as FSB x 2 (because it's DDR) x Ratio
- PC2700 memory (333 MHz) and 133 MHz FSB then the ratio should be 4:5
- PC3200 memory (400 MHz) and 200 MHz FSB then the ratio should be 1:1
The nominal memory speed is the maximum that it can reach. If you mix different types of memory then the BIOS (or manually if the BIOS allows you to do it) will adjust the CPU/Memory frequency ratio without changing the FSB so that the lowest frequency memory operates at it's maximum speed.
And... if you go to your BIOS and don't like the multipliers you see, keep in mind that some BIOS only show in manual mode the multipliers that are compatible with your currently installed memory sticks. They may change when you install different ones.
It is always a good idea to check this multipliers. My ASUS board was set by default at 1:1 with the first example and I had to manually change it to 4:5 to get my memory to run at full pace.
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