[syslinux] Re: Menu system limitations

ganapathy murali krishnan gmurali at cs.uchicago.edu
Wed Apr 28 12:23:43 PDT 2004

H. Peter Anvin wrote:

> Murali Krishnan Ganapathy wrote:
>> The only limit AFAIK is memory. All memory is allocated statically at 
>> compile time. The maximum size for a COM file is 64K. The code plus 
>> all the data should fit into this. Assuming about 256 bytes per item 
>> (that is on the higher side), and 10K for code, and about 6K for the 
>> stack, you have a limit of about 200 items. If you go over the limit, 
>> you should not be able to compile the code (the compiler should 
>> complain that your final executable is more than 64K).
>> If your items can be dynamically generated, then you may be able to 
>> leverage the additional 64K available for COM files (this would mean 
>> changing the code, since currently the code assumes a 16bit pointer). 
>> If you need more than 200 and odd items and they are static, I see 
>> one simple workaround...
>> * Cut your menu tree at some level (say level 2). Then you will have 
>> a mainmenu.com which displays the first two levels of the menu, and 
>> for each possible level 2 choice, you will have a different menu.com 
>> file. Choosing a item from the mainmenu, will call one of the helper 
>> menu.com.
> Well, the simplest way to undo that limitation would be to switch to 
> com32.
>     -hpa
The only disadvantage of com32 I see now, is debugging (burn -> test -> 
reburn ....). Using a CDRW reduces the cost, but the time is still a 

If I am right, the com32 version will have the same menu.* and user 
files. The only files which needs to change is heap.*, biosio.*, startup 
code and some others. Can we setup the code such that, users can compile 
it to an EXE or COM32 by just changing a #define? If so then debugging 
will also not be a problem.

- Murali

More information about the Syslinux mailing list