[syslinux] Updating BIOS with pxe syslinux memdisk & DOS problems

[Alex Ninaber]

Hi James,

I've just tried DOS 6.22 and win98 (download from www.bootdisk.com, quite
useful) but no luck. Still same thing, although with 6.22 it appears to load
1% of the file. 

Alex




> There are several reasons why phlash.exe might not be working correctly.
> 1) One reason might be the DOS version. DOS 6.22 might work, but WIN98
> DOS might not. WIN98 DOS handles result codes from DOS calls differently
> than DOS 6.22, and this might be confusing phlash.exe.
> 
> 2) I have not looked at exactly how memdisk works, but I assume it tries
> to trick DOS into thinking there is an extra disk present.
> Maybe this simulation is not perfect.
> E.g. once I wrote a small program to hook the keyboard, so that if a
> certain combination of keys were hit, I could get certain jobs done.
> During the development of this program, I discovered that if I did not
> restore all the registers properly, strange things would happen. One
> example was, if I changed the SI register for any reason, any Microsoft
> program could not read the keyboard for anything, but any other Software
> worked fine.
> So, maybe memdisk is not supporting the file/open/close api exactly as
> it should, and maybe corrupting a register or two. Normally this should
> not matter, because the DOS API informs us that the programmer should
> assume that no register's state is preserved during an INT21 call, but
> it just so happens, that with some normal DOS calls, some registers are
> preserved, so maybe the programmer got lazy, and did not save all the
> registers before a call as it worked fine with normal DOS, but of course
> might fail with memdisk.
> 
> This is all just theory, as I have not looked at the source code, but
> maybe worth considering.
> 
> Cheers
> James