mixing different types of RAM ok?

[kyu614]

my friend has an old computer and i know for sure it can use PC66 ram. i was wondering if it would also use PC100 or PC133 ram as they are cheaper. thanks

 

[Lord Evermore]

Technically yes. But many modules no longer have the programming in the SPD chip that tells the motherboard chipset what settings to use below 100 or 133MHz. So putting it into a motherboard that is auto-detecting the speed it will fail. This is most common in OEM computers where the BIOS is very limited.

If the BIOS has options that allow you to manually set the memory speed and timings, then you can use faster memory and manually set it to 66MHz. Or make sure to get a module that says it can work on PC66 boards.

You can use the memory configurator at crucial.com to find a module that will work for sure.

 

[Zepper]

Heck, I didn't remember there even was such an animal as PC-66 SDRAM (and I started out with DIP chip RAM)... Sometimes a BIOS update will allow some mobos to recognize the faster modules.
Or as Lord E said, maybe your BIOS will alow you to set the timings manually.
.bh.
:beer: time!

 

[jackschmittusa]

Many of today's pc100 and pc133 sticks are not compatable with older mobos with a 66mz fsb at all. Check a site like Crucial and see if they list multiple modules for the old rig.

 

[kyu614]

Thanks for the replies

You can use the memory configurator at crucial.com to find a module that will work for sure.

I tried that, but his motherboard is not on the list. Its some old company called JBond, i even tried to google it but couldnt find the information i needed. Does anyone have any info on this company?

 

[Lord Evermore]

Is this a system someone built for him, or that he got at a local shop, or an OEM?

PC133 is never "not compatible", it's sometimes just not automatically configurable. You can always manually set the speed and it will work, if the system supports manual settings.

 

[kyu614]

he got it at a local shop. i will have to see what options he has in his BIOS this weekend.

 

[jackschmittusa]

Lord Evermore
Some older mobos are supposed to be unable to recognize the chip configuration on newer sticks and has nothing to do with the speed.

 

[Lord Evermore]

That's a separate issue from whether the module is rated for PC66, 100 or 133, though. PC133 that is low-density will still work in an older board if you can manually set the speed, though high-density might not.

 

[Wallysaurus]

Early Pentium PC's with the Intel VX chipset require a certain kind of 66 MHz RAM. I donate some of my time to a local school and many of the older Pentium 166 and 200 MHz systems require this RAM.

 

[Lord Evermore]

And what "certain kind" would that be? VX supported SDRAM or EDO memory. It had limitations on the density and total module size, of course, just like all chipsets.

Supposedly if the memory has a SPD EEPROM it isn't supported, but I can't see why having that would actually stop the memory from working, if the chipset isn't designed to read it at all.

 

[TheCorm]

I have found that certain generic brands of PC133 do not get fully recognised in some older PC66 / PC100 based motherboards.....on several occasions was a 256mb PC133 stick recognised as 128mb...maybe the same with branded sticks too!

Jamie

 

[Lord Evermore]

That was most likely due to density issues, and limitations on the total amount of supported memory.