I notice on the Damn Small Linux page that they use Kernel 2.4 because it is smaller (I assume this is hard disk space as oppose to memory footprint) and because 2.6 drop support for legacy hardware.

What sort of hardware support does Kernel 2.6 drop? What is consider old hardware any way 386? 486? Pentiums? ISA bus, AGP?

What is usually dropped is actually the drivers, if no one will support it. The Linux kernel is under continuous development, and that means that drivers sometimes have to be updated. If no one claims a driver to provide the updates, then that driver gets dropped.

The reasons that a driver go unclaimed are numerous. Perhaps the hardware is so rare, it's simply not worth the effort. Perhaps the necessary skill set left with a developer. Perhaps the developer has a job now that requires an intellectual property agreement (preventing GPL development).

In the case of DSM, the distribution is oriented toward old hardware - 486+16MB RAM. In other words, systems that have about 1/100th or less resource than current systems - considerably less even than a PDA! Aside from the developers that work on creating distributions for these systems, there isn't a lot of interest, even if the skills still exist.

They dropped my old SCSI card An Advansys I think it was. Because of lack of manufacturer support.

In fact all the code was still there. There was just some switch in the config mechanism that stopped it appearing in the config process. So it was not hard to put it back in, and it continued to work OK until I retired the ancient CD-writer that used it.

Anyway, worth checking the kernel code if you really need that old hardware with a 2.6 kernel.

How would one check which hardware is depreciated in a new Kernel release? Is there a list somewhere?

Secondly, macemoneta mentioned that DSM was geared toward ultra old hardware like a 486. I heard of Linux being used in embedded systems. Are they using a totally different kernel then?

Thanks.

Embedded systems use either the 2.4 kernel or the 2.6 kernel, depending on their needs. For example, the OpenZaurus project, which support Linux PDAs, uses the 2.4 kernel on some models, because the Secure Digital card interface is proprietary (no source code). Other models that don't have the hardware dependency can use the 2.6 kernel. Same issue, different platform.

You can see all the changes in the kernel at the kernel development site.