PC100 - PC133 memory question

[richardm]

Quick question. If I was to put some PC133 memory into a motherboard that supported PC100, could I expect the memory to work correctly?

Thanks!

 

[richardm]

Found an answer myself here :

The PCxxx and CASx names are simply ratings of what the RAM is capable of running. For example, PC133 SDRAM is guaranteed by the manufacturer to run at 133MHz. This 133MHz is not a required operating speed; it merely indicates what the RAM is capable of. The same applies to the CAS rating.

....

Because the PCxxx numbers are merely ratings, there are usually no problems mixing different RAM: PC100 SDRAM will operate perfectly fine together with PC133 SDRAM, using a 100MHz FSB.
....

All SDRAM is backward compatible and can run at any bus speed slower than it is rated to run.

For example, a PC133 SDRAM DIMM is capable of running at 133MHz, 100MHz, and 66MHz.

Excellent

 

[shanek]

Yes, as you've discovered, you can go down.

You can also go up, i.e., put a PC100 memory chip in a PC133 slot, BUT you are overclocking the memory. It might be able to take it, or your system might start crashing more.

 

[DangerousBeliefs]

Yes, but might I suggest two things.

1) Make sure you are using the SAME manufacterer and chip types. Mixing RAM chips on the same motherboard generally causes HEADACHES long term.

2) If you need to use PC100, might I suggest a newer computer? One can be had from as little as $500 these days.

 

[a_unique_person]

Yep, PC100 is so last century.

 

[Trollbane]

1) Make sure you are using the SAME manufacterer and chip types. Mixing RAM chips on the same motherboard generally causes HEADACHES long term.

This shouldnt be a problem unless you use non-JEDEC standardized mem blocks or you use too aggressive mem settings for the other mem block to cope with.

Generic RAM modules work just fine regardless of the manufacturer as long as you set the timings and the bus according to the slower module.

At the moment my rig is running just fine with one 256/266Mhz block and one Crucial 256/333Mhz block.

 

[DangerousBeliefs]

This shouldnt be a problem unless you use non-JEDEC standardized mem blocks or you use too aggressive mem settings for the other mem block to cope with.

Generic RAM modules work just fine regardless of the manufacturer as long as you set the timings and the bus according to the slower module.

At the moment my rig is running just fine with one 256/266Mhz block and one Crucial 256/333Mhz block.

I know this is an appeal to authority with a dash of anecodotal evidence... but I've been working on computers for close to 20 years... and most people are just better off going with the same manufacterer and memory type. Too often, I've had people bring me a computer with a problem and it's because of differing chips.

I also wouldn't recommend the cheapo generic RAM. It's well worth the extra $20-40 to get quality RAM from Kingston or Crucial... especially given the incredibly low prices these days on RAM.

 

[LTC8K6]

The only problem you may run into is an older system not liking the newer, high density modules.

An easy way to tell is that the memory reads as only half the size it's supposed to be. A 256meg module comes up as a 128meg, for example. This usually means that you have a 256meg high density module that is not compatible with an older motherboard.