Back in the way early '80s, even before I became a dad, I was an operations and tech support manager for a mid-sized IBM mainframe installation. We had a room sized monster (by the standards of the time) 3031-AP with eight whopping megabytes of memory, two processors each running at a million instructions per second, and a bank of eight model-3380 disk drives at about 2-and-a-half gig apiece.

That was heady stuff, and we had a bisynch network that reached out to a hundred locations, a big batch workload and probably 150 simultaneous online users at any given time.

At the software center of our world was IBM's flagship operating system, MVS. I was once upon a time very well versed in that system, and considered myself an expert systems programmer. The source code was available back then, and in fact the original version of the operating system was in the public domain. Later versions were copyright IBM and chargeable, but in 1981 we were still running the "free" operating system on the unbelievably expensive hardware.

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Thirty years later we have cell phones that are vastly more powerful and have more storage than that entire machine room that I took care of Way Back When. So it occurs to me that I can revisit my misspent youth, and put MVS up on my new N900. Why not? I've got a couple of Bass Ales in the 'fridge and nothing on TV I care to watch.

So what do I need?

• qole's Easy Debian
• Roger Bowler's "Hercules" mainframe emulator
• x3270, telnet and xterm
• Volker Bandke's "Tur(n)key MVS" disk images

Easy Debian installed via app manager in a couple of clicks. Hercules, x3270, telnet and xterm installed in the Debian chroot with a couple of apt-get installs. The MVS system itself was a bit problematic; it is downloadable as an iso filesystem within a zip file. But the N900 Linux kernel doesn't have loop block support, and I couldn't mount the iso filesystem, so I mounted it on another Linux system and then copied the directory structure over to the N900 via scp.

Start the system with Volker's handy "xstartmvs" script, and IPL (um, "boot") MVS under Hercules - et voila! An '80s vintage MVS springs to life, with console support, a usable TSO, and several compilers.

I log on, edit and submit a quickie PL/I compile-link-and-go job ("Hello world"... of course), and 11 seconds later it completes. That's not very different from the response time I was getting on the room-sized 3031 in the days of yore, but I'm carrying this data center in my pocket.

It has no possible practical benefit, but enormous hoot value. I'm really enjoying this N900.