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SubjectRe: Encrypted Swap
Richard B. Johnson wrote:
> Errrm no. All BIOS that anybody would use write all memory found when
> initializing the SDRAM controller. They need to because nothing,
> refresh, precharge, (or if you've got it, parity/crc) will work
> until every cell is exercised. A "warm-boot" is different. However,
> if you hit the reset or the power switch, nothing in RAM survives.

This does not match my experience building SDRAM based embedded systems.
Initialising SDRAM simply tells the chips what CAS latency to use, and
does not erase the contents. SDRAM is fully functional before you have
written to every cell.

It's possible that JEDEC standards recommend that boot firmware should
erase the contents, and it is certainly necessary to erase before
enabling ECC or parity error detection.

Adrian Cox

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