11 Feb 16 22:57, you wrote to all:

 CS> Hi folks, I have a few questions regarding a 1987 IBM PS/2 Model 25
 CS> I've been tinkering with:

 CS> 1) Is the Model 25 capable of color? If so, how do I enable it in DOS
 CS> 5.0?

There are several different Model 25s but only some are colour. It's
possible yours is VGA but only has a greyscale monitor.

An quick way to test whether you've got VGA with MS-DOS 5.0 would be to run
this in QBASIC:

SCREEN 12
CIRCLE (200, 200), 50, 4
CIRCLE (200, 200), 100, 2
CIRCLE (200, 200), 150, 1

This switches to 640x480 graphics mode (16 colors) and displays red, green
and blue circles on the screen.

If you get an error or a blank screen you probably have a monochrome graphics card.

If you get grey circles on the screen, you have a greyscale monitor.

 CS> 2) What telnet clients are available for DOS 5.0?

mTCP Telnet should work. You'll just need to find the correct driver for
the PS/2's network card, though.

http://www.brutman.com/mTCP/mTCP_Telnet.html

 CS> 3) Would it be possible to install and run Linux via dual-boot on one
 CS> of these computers?

Linux requires at least a 80386 CPU, however most PS/2 Model 25s have
either 8086 or 80286 CPUs.

Even if your PS/2 is a 386SX model, you're unlikely to have enough RAM
onboard to boot the Linux kernel, nor sufficient disk space to install the
base OS.

Something like Xenix might boot on your PS/2, but it'll be painful to use.
For that machine I'd stick with mTCP on top of MS-DOS.

 CS> I've been getting into vintage computing as a hobby lately, but there
 CS> are some things I need help with from time to time. Thanks all and I
 CS> look forward to hearing from you!

I wish I'd kept some of my older PCs, but they can be a real pain to keep going.

Currently my oldest PC is from 1995, unusually with a Cyrix 6x86 CPU. To my
surprise the onboard battery is still working, keeping the clock ticking
over and BIOS settings intact.

I also have a working Pentium 90 motherboard, but no case to put it into yet.

Have you looked at emulators? Running DOSBox, VirtualBox or PCem-X on a
modern PC can be useful. Obviously it's not the same experience as using
the real thing, but it can be very handy for experimenting with software
before running it on real hardware.

There's also the http://www.pcjs.org/ web site, where you can emulate early
PCs entirely in a modern PC's web browser (using JavaScript).

Regards
Andrew

--- GoldED+/BSD 1.1.5-b20160201