>> No. You could just load the contents of the files and
>> execute them so you don't have to provide a letter.
> You cannot "just load ... and execute", you would have
> to do it at the right moment etc.

Of course, but my point was that you won't have to provide a drive letter.

> In particular, you
> would load SHSUCDX after all DEVICE lines, so you had
> to keep it waiting in RAM all the time. In addition,
> you want some user control, so it would be good if the
> files are "accessible like files" in config.sys to let
> you use the config.sys menu function if you ask me...

So that you could, say, debug your CONFIG.SYS not to load SHSUCDX and/or  
ELTORITO.SYS? Why? After all, it would be a special kernel binary used to  
boot CD-ROMs only, so you would usually want to load both.

> But if you do really ask me, all this is getting much
> too complicated [...]

Yes. That's the reason I suggested not to build CD-ROM no-emulation boot  
support into the kernel. Well it's still interesting to think about the  

>> when not using the disk image approach the kernel would have to know
>> the exact position of the files anyway. You could just include the
>> binaries in a NASM source file (think with incbin) and let NASM declare
>> the position as global label.
> When really forced to combine things, I would just use
> COPY /B prekernel.exe + file1 + file2 prekernel2.exe

The kernel then had to know file1's and file2's size which is no usable  

> before doing the UPX and header messing,

Rather stop messing with headers and UPX and create a new compression tool  
(or UPX binary format) for the kernel. Even if you did it with copy /B ...  
and then the UPX hack, won't it be easier for the user to use the build  
script to compile a new kernel which incbins the files instead of using  
copy /B and UPX manually?

> also making
> the latter more advanced to know file sizes and offset
> etc.

Yes, to make it more of a bad hack? Or do you want to write a linker?

> But as said, I prefer not to put raw files in the
> kernel at all.

C design limitation? ;-)

>>> Note that our boot sector already can boot > 64k kernels.
>> If the kernel doesn't relocate itself later that's fine.
>> If it does, the relocation code also has to handle > 64 KiB.
> Correct, kernel_start cannot copy more than 128 kB yet
> but as always deep inside the kernel memory model and
> startup code, structure is complicated and adding more
> areas such as "embedded files" would make things a lot
> more complicated.

If you say so. I rather think when you already added support for 128 KiB  
data moving (requires accessing the data from two segments), more can't be  
that difficult.

>> This would require the kernel to be compatible enough
>> to post-CONFIG state when only pre-CONFIG
> I would not call this compatible, rather incompatible.

Well, then someone would (!) need to *make* it compatible. DOS doesn't  
have to be incompatible to post-CONFIG. Because pre-CONFIG is so unknown  
no one even cares whether DOS is incompatible there. (In fact, as with the  
"S" MCB allocation, a post-CONFIG compatible DOS might make things easier  
for the CONFIG.SYS parser.)

>> Both driver and redirector would have to stay in low memory unless you
>> also embedd XMM and EMM in the kernel/include it on the embedded disk
>> image, or write some special code to relocate the driver...
> All this is getting so complicated and unusual that I
> would say you should at most try this in experimental
> operating systems, not in mainstream DOS kernels ;-).

Of course the great DOS-C development strategy would be to split all  
developers in two branches here, one "mainstream" and one "interesting".

>>>> Why is the source code (of eltorito.sys) not available?
> ...
>> Aww. What a polite guy.
> No, just a normal guy. Making sources available is work, and if
> nobody pays you and nobody even asks you for them, why should
> you spend time to publish them?

Didn't "apparently few people" ask? Is that the same as "nobody"?

> But feel free to politely ask
> Bart of nu2.nu to publish his sources, to conserve the collected
> knowledge of BIOS compatibility tricks of ELTORITO.SYS and make
> people who want to tune or update this good old tool happy :-).

I'll do so if I ever want to boot from a CD-ROM in no-emulation mode.


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