Messages in this thread | | | Date | Fri, 17 Aug 2001 13:21:25 -0400 (EDT) | From | "Richard B. Johnson" <> | Subject | RE: Encrypted Swap |
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On Fri, 17 Aug 2001, David Christensen wrote:
> > > Ryan Mack proclaimed: > > > > is running. If the system is physically compromised, > > there is little way > > > > I can think of to take root without having to at least reboot the > > > > computer, thus destroying the unencrypted contents of RAM. > > > > > > This is a myth. RAM survives rebooting, even after a quick > > power cycle > > > most cells will probably still be ok. And with todays > > memory sizes, it > > > would take a noticable amount of time to initialize all of > > it to a given > > > value, so most systems don't do it (just testing some bytes of every > > > megabyte instead). > > > > > > Holger > > > - > > > > 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. > > Most modern firmware does NOT clear memory during POST, it takes too long. > Certain compatibility areas are usually cleared (such as the 1st megabyte) > but the rest is > left as is, except for a few read/writes (usually on a megabyte boundary). > The > exception to this rule is ECC systems. They have to be written to make sure > the > ECC information is correct. > > SDRAM memory sizing is usually done by reading an EEPROM on the SDRAM DIMM. > The BIOS doesn't need to guess the correct timing values, it simply reads > the EEPROM and programs the memory controller. In the case of a BIOS that > doesn't use EEPROM you might lose data as the BIOS iteratively tries > different memory timings and tests if they work. > > I have done work implementing ACPI S3 (suspend-to-RAM) in DOS by simply > hitting > the RESET button and restoring the memory controller settings. The contents > of > RAM have always been valid. > > David Christensen >
I just posted working SDRAM controller initialization code. The SDRAM controller must be initialized in a specific step-by-step manner or else you don't even get to "restoring the memory controller settings".
Cheers, Dick Johnson
Penguin : Linux version 2.4.1 on an i686 machine (799.53 BogoMips).
I was going to compile a list of innovations that could be attributed to Microsoft. Once I realized that Ctrl-Alt-Del was handled in the BIOS, I found that there aren't any.
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