[syslinux] memdisk and winxp boot disk

[H. Peter Anvin]

Giulio Orsero wrote:
> On Wed, 19 Jun 2002 10:18:43 -0700, "H. Peter Anvin" <hpa at zytor.com> wrote:
> 
> 
>>I see.  Either way, there is nothing MEMDISK would have to do with 
>>anything then, since I gather he's using a floppy image.
> 
> 
> The above is because if you use a normal floppy image you shouldn't need to
> use memdisk, because "kernel floppy.img" is sufficient, right?
> 

For ISOLINUX only... and only theoretically, because it appears 90% of 
all BIOSes get this particular feature wrong.  Really.

> The problem is that I found out that memdisk is preferable even for normal
> floppy images:
> 
> A) winxp floppy image:
> A1) kernel floppy.img
> Says "there's a problem with winxp installaion or disk, reinstall windows"
> A2)  memdisk + append initrd=floppy.img
> Says "cannot find file <windows>\system32\x, reinstall file x"
> So I assumed memdisk did something better.
> 
> B) another dos floppy image
> B1) kernel floppy.img
> error "drive a: is write protected  abort,retry,ignore", 
> "ignore" allows to go on ok;
> there's nothing in autoexec.bat or config.sys (the message is right after
> "Starting MSDOS) writing to the image and the real floppy can be booted
> write protected;
> B2) memdisk + append initrd=floppy.img
> no error, normal boot
> 
> The above cases are with vmware bios, ok, it is not real :-)

Wow, it looks like they actually got the image feature right (and yes, 
it's readonly if you use the "kernel image" feature, whereas you can 
write to a MEMDISK.)

> With Asus ACPI BIOS the memdisk method works perfectly, the "kernel
> floppy.img" fails completely "invalid file name" or something similar (does
> not even try to boot).
 >
> So it seems memdisk can overcome some bios problems, this is why I use
> memdisk for floppy images too.

It can, indeed.

	-hpa