OK, for more comparative data I installed "Damn Small Linux" on a 200mhz Pentium with 32 MB RAM and 500 MB HDD.
I found that it uses 9.4 MB RAM (when set to JWM window manager)
(it looks exactly like the attached pic, only the pic is not mine, it's from the web so the ram usage shown is different)
It looks like it would turn an old PC into a nice workstation, I am unsure how to make it useful for MAME but I would imagine you could install XMAME on it.
Below is the install guide I used
preparing the hard drive
I booted the DSL CD with boot option dsl 2.
From the command line I typed:
(This brings up the Linux version of "Fdisk") I made two partitions hda1 type 82 100Meg for swap and hda2 type 83 for the rest.
Then I typed mkswap /dev/hda1, mkfs.ext2 /dev/hda2, and swapon /dev/hda1
Installing DSL linux to the hard drive
1. Boot the computer from DSL Linux CD, at the prompt press enter
2. Once DSL linux has started and you see the desktop - right click the desktop, choose Apps > Tools > Install to hard drive
3. When asked what partition type hda2, answer yes to start install
4. after install is done it asks if you want to install the boot installer > yes
5. When asked what boot loader press "L" and enter
5. after that it asks if you want to reboot > yes. Remove the DSL Linux CD from the CD-ROM drive
Once booted from hard drive I right clicked the desktop and chose "window manager > switch to JWM"
It changed the desktop to JWM and shows the RAM usage as 9.4 MB (out of 32 MB)
Here are some advanced instructions to turn the PC into a better workstation :
When it reboots, you have a very simple machine. A few web clients, VI (a crippled Vim), several other apps. Enough for simple computer usage, but not what you'd call a real desktop machine.
The installation does not have a functional apt-get or dpkg. You need those if you want to do anything more than browse the net and get email. To enable them, be sure your Internet connection is working and connected, then right click the desktop, then Apps->Tools->Enable Apt. The computer will take quite a bit of time downloading more stuff.
The Fluxbox window manager is nice, but if you're like me you prefer a taskbar and start button. The IceWM window manager is almost as efficient as Fluxbox, and it has a start button, task bar, and network and CPU monitors on the taskbar. Install IceWM as follows:
apt-get install icewm
The computer will download and install IceWM. To enable IceWM, edit the /home/dsl/.xinitrc file. Comment out the line that runs fluxbox, and substitute the following:
# set mouse speed
xset m 5 2
# start xterm by default
# silently check if icewm is in your $PATH and start icewm when found
# or a red colored xterm when not found or execution of icewm fails
which icewm >/dev/null 2>&1 && exec icewm || exec xterm -bg red
The result is a rather hard to see black version of IceWM. You need to change the theme. Do so by creating a .icewm directory under the home directory, and creating a preferences file containing the following:
ShowThemesMenu=1 # 0 / 1