We want to upgrade RAM of our legacy Pentium IV and Pentium III systems from 256MB/512MB to 1GB/2GB.
Is there a limit on the MHz speed of the RAM which any motherboard can support or is it that the motherboard will automatically downclock the RAM to the actual speed, even if we fit any higher/lower speed RAM on the motherboard.
For ex. the existing RAM may be 533/400/667 MHz, but can we fit 800MHz RAM on that motherboard. Or is it that we have to fit in RAM of exactly the same configuration as that already fitted in.
You need to check the motherboard -RAM compatibility.
Most boards will have a memory compatibility list whioch will state all teh details regarding what memory you can use. If you cannot find a memmory compatibility list, then look in the motherboard documentation. On intel boards the technical product specfication or TPS
The method suggested by you (checking the datasheet) would be useful for a few systems (one or two). Howver, if we want to upgrade 400 systems, then searching for manuals/datasheets for 400 systems separately is a tedious job and probably impossible considering the fact that the manuals would not be available for such old systems.
Is it possible to generalise the assessment so that we can procure RAM in bulk for all the systems. Or else is there any software available which can help us in assessing the RAM compatibility with the systems -either on the network or individually.
Not that i am aware. Are all the motherboards the same? The thing is that if they are that old they may not support more than 1 Gb or 512 etc.... If the motherboard are not teh same how can you generalise?
So yes there will be a limit to the speed you can put in the motherboards. There will also probably be a limit to teh amount of memory you can put in these board. So you could generalise and get 400 modules of ram.. say 400mhz sounds safe...but whether you will be able to use them or not is a different matter.
If you tell us the motherboard models maybe i cna be more specific. But to be honest you are expecting magic
It depends on the motherboard(s) that you have your processors installed on. No legacy Pentium III system has any DDR2 slots at all. Most PIII systems used plain SDRAM; a few used RDRAM. If your PIII system used SDRAM, it ran memory at only 66 to 133 MHz.
Early P4 systems also used RDRAM or plain 133MHz SDRAM. Later P4 systems began to use DDR memory running between "266MHz" and "400MHz" (actually 133 to 200 MHz) - and still later systems used DDR2 memory. None of the different memory technologies are compatible with one another; in fact, the pin assignments and notches are different enough so that one type of memory will not even physically fit the DIMM or RIMM slots designed for another type of memory.