[rescue] Oh no! This poor Origin server.....

Dave McGuire mcguire at neurotica.com
Thu Apr 1 16:19:15 CST 2004

On Apr 1, 2004, at 5:00 PM, Lionel Peterson wrote:
>> No, but I understand one can pick up quantum charge
>> fluctuations and read, with some accuracy, the "last
>> powered-on state" of a DRAM cell.
> What, DRAM? I could see maybe for Static RAM, but DRAM (by design) 
> loses it's state without a near constant refresh (as I understand it, 
> but my understanding here is minimal).

   Well...a DRAM cell (bit) consists of a capacitor and a 
transistor...the capacitor loses its charge in a few milliseconds due 
to dielectric leakage, so it must be refreshed.  DRAM cell reads are 
destructive, so the support circuitry is designed to replenish the 
charge on the capacitor with every read.  So to refresh the entire pile 
of bits, you just make a read pass through them.  There's a bit more 
detail than that (like entire rows in the bit array are typically 
refreshed simultaneously) but that's the basic gist of it.

   And I believe the idea here is that a SQUID could detect the tiny 
(literally, a few electrons) residual charge on the capacitor.


Dave McGuire          "PC users only know two 'solutions'...
Cape Coral, FL          reboot and upgrade."    -Jonathan Patschke

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