Aren't all the Linux distros based on the same kernel?

If so, why is it that Mandrake wouldn't recognise my sound card (never ever got it working) but recognised my serial modem without hesitation.

But, Ubuntu recognised my sound card and I needed to tweak the modem to get it to work (and now it works fine.)

The above is just an example of hardware detection differences. Throughout this (and other) forum(s) I read a lot about various distros not recognising or immediately recognising different hardwares.

Why the discrepancies? It's all Linux?

I'm sorry if this is a dumb question, I'm still a newbie - despite my growing number of posts.

EDIT:

I don't know how or why that web address appeared in the Subject line. Could a moderator fix it?

First, there are different versions of the kernel.

Second, what hardware is supported is determined by what drivers are compiled into the kernel or as kernel modules.

While, yes technically they all use the same Linux kernel, they are by no means all identical.

Different distros use different approaches to hardware detection and configuration. This is done with scripts and detection/config apps. If all were identical, there wouldn't be so many different distros.

all distros are based on the same kernel source and have the same compiler. each distro then compiles the kernel differently which is why hardware is supported differently. the way hardware is detected and modules are loaded are also flavored to the liking of the distribution developers.

but to the best of my knowledge if hardware is supported by default in one distro any distro can be configured to support the same all other things being equal.

True, but sometimes a little more 'tweaking' is involved with getting the hardware working. Distro's apply patches to their custom kernels to make them just that, custom. Not every distro applies the same patches, and usually you have a few sets of kernels to boot from as a result of a normal install.

As for them all being compiled by the same compiler, that's not always nor completely true. Depending on their release date, and version of gcc from that release, the compiler (unless you are referring generally to gcc) version could be completely different from distro to distro, sometimes keeping you from being able to grab modules from one kernel and 'inject' them into another.

Cool