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

[James Courtier-Dutton]

H. Peter Anvin wrote:
> James Courtier-Dutton wrote:
> 
>>>
>> 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.
>>
>> This is all just theory, as I have not looked at the source code, but 
>> maybe worth considering.
>>
> 
> It's not really a theory.  It's an enumeration of things that might 
> contribute.
> 
> Using Win98 DOS is *known* to cause problems, because bugs in Win98 DOS 
> that trigger for MEMDISK (as well as several other combinations of things.)
> 
>     -hpa
> 
> 
> 
I did not find bugs in Win98 DOS. All I found is that the return codes 
from DOS INT calls were different. For example, DOS 6.22 returns the 
same error code for "file not found", and "path not found", but DOS 7 
(Aka. Win98 DOS) returns two different error codes. This change in error 
codes confuses a lot of old DOS programs that were not expecting them.
When I contacted MS regarding this, they informed me that DOS 7 was 
doing it this way as an enharnacement, and not a bug. It is possible in 
one's program to check for MS DOS version, and act differently depending 
on what it returned. Some MS DOS programs actually refuse to run if not 
being used with the correct MS DOS version. It seems that very few 
programs apart from MS written ones, bother with the MS DOS version check.

Cheers
James