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Re: Does reboot clear RAM?

From: Joachim Durchholz
Subject: Re: Does reboot clear RAM?
Date: Wed, 13 Nov 2019 07:27:26 +0100
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Am 12.11.19 um 02:20 schrieb Jakob Bohm:
On 11/11/2019 20:27, Joachim Durchholz wrote:
Am 11.11.19 um 15:35 schrieb Jakob Bohm:
On physical machines, the following mechanisms are common:

1. DRAM chips physically loose their contents after a few seconds of power

I am by no way an expert, but the forensic experts tell me that data can persist for *minutes*. Of course, the first bits flip after a few seconds. But you don't get a guarantee that everything is zeroed.
I also hear that temperature plays a really big role here.

There's a difference between reading faded bits with special analogue equipment
after artificially cooling chips way below what the datasheet allows, and
reading the digital bits at normal temperature, voltage etc.

The refresh circuitry of a DRAM chip is just for the purpose of reading faded bits. And of course it will read whatever it decides is in the cell. If enough electrons are left, it will be above the threshold, so you can expect to see the occasional 1 bit in RAM unless it's cleared.

I'm still interested in hearing whether typical RAM has a RST line and whether that wipes memory (or merely initializes internal circuitry). Speculation about potential low-level circuit trickery is nice but does not answer that question, I fear.


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