[sci.electronics] Why SRAMS in Mac Laptops?

watt@eleazar.dartmouth.edu (Gill Watt) (03/01/91)

howdy,

I have a curiosity question:

Why do the mac laptops use SRAMS instead of the standard
DRAMS?

Is it because DRAM refresh circuitry consumes a lot more
power?  If so, how much more?

Anyone know any other reasons?

Thanks.





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Gill Watt (watt@eleazar.dartmouth.edu)
Thayer School of Engineering, Dartmouth College, Hanover, NH  03755
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henry@zoo.toronto.edu (Henry Spencer) (03/02/91)

In article <1991Mar1.020935.7107@dartvax.dartmouth.edu> watt@eleazar.dartmouth.edu (Gill Watt) writes:
>Why do the mac laptops use SRAMS instead of the standard DRAMS?
>Is it because DRAM refresh circuitry consumes a lot more
>power?  If so, how much more?

It's not the refresh circuitry so much as the DRAMs themselves.  DRAMs
simply are not low-power technology.  The right sort of SRAMs are.

There is no single meaningful answer to "how much more".  It can be orders
of magnitude, if you really work at making the SRAM system economical.
In particular, where DRAMs draw milliamps, SRAMs in low-voltage standby
typically draw nanoamps.
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