[plug] older laptop ram compatibility and availaility

[Arie Hol]

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, 
although
> the websites tells you that you can use PC100 rams [sic], but most of 
the
> time the PC100 ram will not work together with the onboard ram, you 
must
> 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 
probably
> 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 
PC100. 

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

HTH

Regards Arie
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