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Hi, |
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On Thu, 4 Oct 2007 15:47:53 +0200 Alan McKinnon |
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<alan@××××××××××××××××.za> wrote: |
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> On Thursday 04 October 2007, Liviu Andronic wrote: |
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> > And later on: "Now one problem is |
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> > left. Even with normal RAM a well funded organisation can get the |
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> > contents after the system is powered off. With the modern SDRAM it's |
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> > even worse, where the data stays on the RAM permanently until new |
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> > data is written. |
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> |
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> Pray tell, how does RAM manage to retain data when the power is off? |
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> It's either six transistors or one transistor and a cap per cell = |
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> not persistent. |
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In theory, for the one transistor and one cap case, you have a loaded |
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cap that will take "forever" losing its load, won't it? But in |
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practice, I think, that's not realistic. |
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> I don't know of any magic persistent RAM that's fast enough for use |
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> as main RAM. Flash disks are of course another story but you do |
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> appear to be talking about system RAM |
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There actually are new RAM types being made for solid-state storage. |
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But this is in a proof-of-concept stage, I think. |
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Maybe Liviu's professor had those magnetic drum memory units in mind |
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when saying that? |
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Anyway, cleaning memory on a power-off shut down doesn't make much |
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sense. However, it makes sense to clean up memory after having critical |
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data in it -- e.g. a reboot doesn't necessarily clean up RAM. And I'm |
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not sure if some mainboards even keep the RAM powered in certain |
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situations -- at least, they can as long as the power is not really |
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switched off (e.g. machine only in ATX soft-off mode). |
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|
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-hwh |
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-- |
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