RAM Boot problem feedback to Saad Syed

[Slobodan Brcin]

I was arrogant enough to think that I would be able to write custom boot
loader that will work in one day.

Well I was able to write it in one day and appropriate utilities also, but
it didn't work
Two days later I found out that it is working but that I can't use
0x00200000 memory address for loading SDI image. It looks like ntdetect.com
clobbered data in that memory.

Now I'm loading SDI image close to end of physical memory, and everything is
working fine.

But I would like to know for certain if XPE is aware of this memory or is it
protected by Windows RAM Disk Driver.
Because I don't want any more surprises. Could you confirm that this is ok
and that additional restrictions on memory that XPE can access are not
required.

You should upgrade info on at least what memory range is off-limits in
article
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnxpesp1/ht
ml/ram_sdi.asp

This doc is excellent but it misses info on where should we load SDI image.
(Or at least where we should not load it.)

BTW: There are other ways to load SDI to memory above 1MB.



Keep up good work,
Slobodan Brcin

 

[Saad Syed [MS]]

Slobodan,

Thanks for the feedback. I'll try to define the memory limits in the
whitepaper. NTLDR needs some working set before it is able to initialize the
ramdisk, even before that startrom.com needs some memory to load NTLDR.
You'll be ok, if you load the ramdisk as high as possible (which is what you
seem to be doing). I'm curious why you wrote your own boot program, where do
you the SDI from? If its on a harddisk you could've used the /RDPATH and
/RDIMAGEOFFSET switches to read the image directly into memory off the
harddisk or cdrom, just like its read into memory in remote boot.


Thanks,
- Saad, MS

This posting is provided "AS IS" with no warranties, and confers no rights.

 

[Slobodan Brcin]

Saad,

NTLDR needs some working set before it is able to initialize the
ramdisk, even before that startrom.com needs some memory to load NTLDR.
You'll be ok, if you load the ramdisk as high as possible (which is what you
seem to be doing).

I know that now, but for me it would be better that I knew it before I
encountered problem.

I'm curious why you wrote your own boot program, where do
you the SDI from?

Currently from Removable USB Flash Disk. I need deployment environment for
devices without network, and CD drive. Since I need XPE image on HDD.

But this was just a test to see if this can be done, since we will need to
encrypt SDI image in our final product.

If its on a harddisk you could've used the /RDPATH and
/RDIMAGEOFFSET switches to read the image directly into memory off the
harddisk or cdrom, just like its read into memory in remote boot.

I was using this to test if my PART section of SDI was ok, nevertheless
Thanks.

Best regards,
Slobodan