Windows Vista PreOS Environment: What happens before the OS loads

Posted By: Charles | Mar 19th, 2007 @ 1:53 PM | 52,229 Views | 14 Comments
What happens, exactly, when you turn your computer on? Yeah, you see the black screen and words scroll by, then, finally, the Vista startup sound... But, there's a good deal of code that runs in this preOS environment, much of it composed in languages you've probably never written (like 16-Bit Real Mode code). What does the BIOS do, anyway? Why do we need a BIOS? Vista can run without a BIOS: It supports UEFI. What's UEFI, anyway?

This is a rare interview with some of the developers nobody sees during the day (Smiley), who live and breathe in the preOS space (this is the single threaded world of pre-operating system start-up context where there is no memory manager, no object manager, no kernel period - it takes highly skilled developers to write code in this memory confined space, the land of real mode code and the BIOS).

Meet Jamie Schwartz, Development Lead, Windows Kernel Dev team, and Andrew Ritz, Development Manager, Windows Kernel Dev team. They tell us all about the wonderful world of preOS. Enjoy.
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#Mar 19th, 2007 @ 3:12 PM
littleguru
littleguru
<3 Seattle
Thanks for this vid... I'm going to enjoy it.
#Mar 19th, 2007 @ 5:47 PM
ZippyV
ZippyV
Fired Up
littleguru wrote:
I'm going to enjoy it.
Weird fetish you have. Tongue Out

Got a couple of questions:
- Why do we have to create a dos floppy to flash a bios?
- Is EFI now supported or not in Vista?
- Are there any motherboard manufacturers that are going to ditch the bios and put EFI on it?
- Can I boot to Linux using the Vista bootloader (without using a Linux bootloader)?
#Mar 20th, 2007 @ 1:27 AM
section31
section31
OutOfCoffeeException
ZippyV wrote:

- Can I boot to Linux using the Vista bootloader (without using a Linux bootloader)?


XP bootloader can also boot a linux. You have to create an image of the linux bootsector. This image file can be loaded by the xp bootloader as well as by the vista bootloader
#Mar 20th, 2007 @ 4:40 AM
PerfectPhase
PerfectPhase
"This is not war, this is pest control!" - Dalek to Cyberman
ZippyV wrote:

- Why do we have to create a dos floppy to flash a bios?


I haven't had to do that for a long time, all my machines (Dell) support flashing from within windows.

#Mar 20th, 2007 @ 5:09 AM
littleguru
littleguru
<3 Seattle
ZippyV wrote:

littleguru wrote: I'm going to enjoy it.
Weird fetish you have.


Tongue Out
#Mar 20th, 2007 @ 5:13 AM
RichardRudek
RichardRudek
So what do you expect for nothin'... :P
So does this mean we are going to get a WinRE video ?

Like with my skillset, I'm seriously considering wether there's any opportunity for someone like me, creating "addons" to WinRE, or perhaps convincing them into allowing some kind of addon API.




Now a direct question for Jamie/Andrew.

I ran into an issue a couple of days ago which I thought had been fixed since Windows 2000 sp2. That is 48-bit LBA on ATA (IDE) Hard disks.

In this case, there was an existing Windows 2000 Server where the Admin needed to setup a parrallel install of Windows on a second D: volume. Now this was a 250MB basic disk volume, and was ~60-70% full. The Admin booted off his Windows 2000 sp4 CD (slip-streamed) and proceeded to through the text-mode setup, installing to D:\WINNT. Upon reboot, entering what should be the 2nd stage, GUI part of the installer, you get a BSOD and a message about D:\WINNT\SYSTEM32\NTOSKRNL.EXE being missing.

Upon my investigation, it became apparent that NTOSKRNL.EXE was well beyond the old 28-bit LBA limitation (~128GB point). But I wasn't able to investigate any further, due to urgency. Is this likely an issue of a bad service pack integration of the Windows 2000 Server CD. That is, the CD was still using the old, pre 48-bit LBA IDE/ATAPI driver(s) ?

PS: I side-stepped the issue by resizing and moving the partition up, leaving a 2GB partition at the start of the disk for the new parallel install.

#Mar 20th, 2007 @ 8:42 AM
liridon shala
liridon shala

Interesting video I'm enjoying it, and what is amazing me is that is running without bios hmm kind of suprised.

 

Great job definitivly !

#Mar 20th, 2007 @ 9:26 AM
AJenbo
AJenbo
Thank you for this video i was dreaming of it this weeks end and here it is Big Smile

Just a few notes here.

Vista does NOT run on PowerPc, Mac have switched from PowerPc to x86 and that is why it can run on them.
Some early edition of Windows NT worked with PowerPc but it was never releasted to the public i belive.
ZippyV wrote: 
Got a couple of questions:
- Why do we have to create a dos floppy to flash a bios?
- Is EFI now supported or not in Vista?
- Are there any motherboard manufacturers that are going to ditch the bios and put EFI on it?
- Can I boot to Linux using the Vista bootloader (without using a Linux bootloader)?


Yes Vista supports loading from EFI.
Yes the bios is beeing ditched VIA and other chip manufacture are working on EFI's to go into pc motherboards as we speek (type).

The grate thing about EFI is that you can have it use hardware better alowing to run the hardrive at full speed on boot up, but sound like the Vista bios bootloader partialy is cabable of this.
#Mar 25th, 2007 @ 3:07 AM
univert
univert
It seems many a lot of guys at microsoft are left handed.
I have seen serveral of them on channel 9.
A very interesting phenomenon.
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