[plug] older laptop ram compatibility and availaility

Arie Hol arie99 at ozemail.com.au
Tue Jun 26 20:17:32 WST 2007

On 26 Jun 2007 at 16:04, Gavin Chester wrote:

> Immediately after sending my last post I found this reference:
> "Please also notice that 256mb PC133 and 512mb PC133 are not backward
> compatible with PC100 rams. [sic] 
> Some old laptops have onboard PC66 ram that can not be removed, 
> the websites tells you that you can use PC100 rams [sic], but most of 
> time the PC100 ram will not work together with the onboard ram, you 
> get PC66 rams [sic] or PC100 rams [sic] that are backward compatible."
> So it seems that from that info and Tomasz's advice that my most likely
> bet would be one ram card is/maybe the only one changeable but it 
> only safe to consider only getting 128mb PC66 unless I find I have two
> removable ram cards. 
> The plot thickens ... Now you can further appreciate why I was jsut
> chasing someone's cast-off ram in case it doesn't work :-) 

If you put PC100 or PC133 RAM into a PC66 rated machine you may need to 
check the voltage requirements/settings for the RAM modules.

The advent of PC100 --- PC133 RAM modules led to changes in voltages, 
which could range from 2.8v, 3.2v - 3.3v, 3.5v and as high as 5.0v.

Also need to consider "buffered" or "unbuffered" as well as the pin 
count, I think it should be 72 pin ( I hope).

I do not know the voltage rating for PC66.

If you can match the voltage with PC66 RAM, it "shouldn't" matter whether 
you use PC100 or PC133 - if the voltages are the same then the faster RAM 
will fallback to speed of the PC66.

EXAMPLE : Using a mix of PC100 and PC133, all RAM will run at speed of 

It's been a while since I worked with PC66 so please correct me if I am 


Regards Arie
 For the concert of life, nobody has a program.

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