Why are some wads (BTSX) split on multiple wads?

[redEYE]

Over the years I've thought that Aliens TC was split in multiple zip files so that people back in 1994 could download it from office or school computer or at friend, store it on several floppy disks and play at home. It wouldn't have fit on one 3.5" floppy.

 

I also assumed that in Aliens TC all sprites and flats were in a separate wad so that DeuSF.exe could append the Doom original sprites and flats with less hard drive reading and writing.

ALITCSF.WAD - sprites, flats
ALITCSND.WAD - sounds
ALITCWAD.WAD - levels, graphics, patches

Aliens TC install.bat reads:

echo Appending sprites&flats to alitcsf.wad.
echo This may take a minute or so.
DeuSF -app alitcsf.wad > alitcsf.log

But - why are BTSX episodes 1 and 2 split on two wads? Is there a practical reason, perhaps in vanilla compatability, for this?

Episode 1:
btsx_e1a.wad - graphics, sprites, music, maps
btsx_e1b.wad - patches, flats

Episode 2:
btsx_e2a.wad - graphics, flats, maps, sprites
btsx_e2b.wad - music, patches

 

[Plerb]

Its because vanilla Doom has a limit on how many lumps there can be in a single WAD file, and BTSX etc go over this limit. Using multiple PWADs circumvents this limit.