Initial revisions of Acorn's "!Internet" software had, fundamentally, a single module doing everything from memory management, tcp/ip protocol layers, and hardware ethernet driving. DCI2 split this up a little, so that the ethernet card drivers were in separate modules, so that each manufacturer could create a driver for their particular ethernet card, and have it used by !Internet. DCI-3 is basically the same. DCI-2 is used by !Internet 2.xx and !FreeNet 1.xx
DCI-4 is the current standard for Acorn internet software. The basic system now comprises of the "Internet" module, a "MBufManager" memory manager, and the "EtherX" ethernet driver modules. DCI-4 is used by !Internet 4.xx, 5.xx and !FreeNet 2.xx.
It's easy to identify whether you have a DCI-2 or DCI-4 setup on your Ethernet card -- check if you have MBufManager in podule ROM. Push F12, and type * RomModules -- You'll see all the 'Rom' modules
in your machine, including the RISCOS modules, and everything provided on your expansion cards. Check those listed for your Ethernet card -- if you see a line
1 Podule0 MbufManager 0.17 Active
then you have DCI-4, if not, it's DCI-2.
So which should you use? Well, it's best that you use DCI-4 where possible. All new ethernet cards have these modules in podule ROM, and the !Boot sequence now has all the DCI-4 modules contained there as well. It's only worth coping withe DCI-2 if you have an old ethernet card which only has DCI-2 modules, and you're using it on a discless machine. If you have a DCI-2 card, you can usually either buy a DCI-4 ROM for the card, or, if you have a hard disc in the machine, you can soft-load all the DCI-4 modules that you need. This is recommended.
This page was written by Ian Jeffray and hosted on his website until 2002, it is now available here with permission