Date: Wed, 20 Nov 2002 09:18:52 +0800 From: Raymond <[EMAIL PROTECTED]> Subject: Re: [LIB] Overlay program wanted
At 08:15 AM 19/11/2002 -0800, you wrote:
Look for posts with the subject "[LIB] 20 gig Fujitsu in an overclocked L50 and working!" and "Experiences trying to get Linux onto this @!#@#$@#$@#$# thing!" in the archives (there's a link to a searchable one from www.silverace.com/libretto if I recall correctly). IBM disk manager is *similar* to EZ-Drive if I recall correctly.Date: Tue, 19 Nov 2002 11:14:14 -0500 From: David Nedved <[EMAIL PROTECTED]> Subject: Re: [LIB] Overlay program wanted Hi Raymond, Thanks for the response... I've given up on keeping my 8gb windows intall. I've gone ahead and intalled IBM disk manager (couldn't find the ez-drive posts you mentioned) and let it create one 8gb partition.
Uh oh ... OK be *very* careful that the partition table is consistent. I had a similar problem (I think it's in one of the speals in the posts up there) where creating things with EZ-Drive enabled then without and getting things horribly mixed up.Interesting that when I went to install version 9.5.7 it wanted to create one partition of 39.9gb (ie it saw the whole drive) but I went back to 9.4.3 which created one partition of 8gb (ie it only saw the bios limited part) and then upgraded to 9.5.7 for the heck of it. Now I've got my 8gb partition, I've got my overlay, and when I boot up fdisk sees the whole drive.
Not quite. Again I think I've got a bit of a thing about this in those posts but in short, the BIOS is loaded into memory and has, amongst other things, INT13h routines for the OS to use to access the hard drive. The problem is these routines on the Libretto don't see above 1024 cylinders. What the drive overlay does is it sits on the MBR and loads before the OS does. It looks for these routines in memory and overwrites them with routines which are capable of seeing 1024 cylinders (it 'overlays' the BIOS's INT13h routines so it should really be called a "BIOS overlay" as opposed to a "disk overlay"). Once it's done that, it then loads the original MBR (which is actually displaced by 8k). Now the problem is this stuff takes up space so part of what those routines do is also trick whoever calls them (ie. the OS) into thinking that the MBR, partition table, etc. starts 8k after what it actually does. Note that it doesn't actually tell the BIOS anything, hence the hibernation area will exist where the BIOS thinks the end of the drive is, which is 1024 cylinders. You will get problems with some programs that do direct IDE access (such as Norton Ghost, which you can force to INT13h mode using the -ffx switch). Linux (at least Red Hat 6.2 and above but IIRC many previous ones) will recognise the existance of EZ-Drive as long as the first partition on the drive was created using something that sees EZ-Drive (such as MS-DOS FDISK) and work around it (it still does direct IDE access but it does the same compensation as EZ-Drive does). Win2k also knows about EZ-Drive and compensates accordingly.I guess I understand a little bit more about how these overlays work now. I guess they install an additional 8k at the beginning of the drive, and then trick the BIOS into thinking it's not there?
Again, have a read of at least the second speal ... it is a bit of a rant but it answers these questions ;-)Now, the way I used to do it was pop the drive into my linux desktop, and manually create the second partition skipping about 80MB or so for the hibernation partition. I didn't have a problem the last time I did it, but that doesn't necesarily mean anything. Am I going to have problems since I'm modifying the partition table with an OS that's not running through the overlay? How else do I create a second partition while skipping the hibernation space?
It will ... if I recall correctly I ended up creating some with Linux FDISK and mucked around with some of them in Partition Magic (which is EZD aware). You could probably do the whole lot (apart from the initial partition) with Linux FDISK but I decided I'd be better off using Linux tools to create the linux partitions and DOS tools to create the DOS partitions.The dos fdisk is so retarded I can't even make more than one primary partition even though I know that the DOS partition table allows for up to 4... all I can do is create an extended partition, and there can only be one, and I'm sure it will create it in the "bad place" at the end of the 8gb...
Hope this helps!
- Raymond
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