Your own AS/400
If you want to have your very own AS/400, the first step is to acquire one. New machines are expensive. Unless you recently won a lottery jackpot, you might want to look for older machines.
There's no known emulation of the AS/400 platform on common platforms available. Virtualization of the OS is available, though. But only on IBM hardware, starting with POWER5 CPUs.
As I pointed out in The Naming of the System, the main differences between older and newer systems are hardware based and not software based. Of course, newer OS releases have more features but I'm questioning their significance for a rookie regarding AS/400.
Facts to keep in mind when deciding which machine would be the right one for a beginner:
Power Consumption
Older machines from pre 2000 need most power for spinning their hard disks. You can add 10..12 W of power for every 3,5"-Disk. Depending on model and how much stuff is in there, you can calculate between 60..300 W for a machine.
Every expansion card needs power to operate. The more cards, the more power. It's usually safe to wade out cards one doesn't need. Some boxes had multiple modems attached to dedicated serial ports. Get rid of them.
Especially power hungry are integrated PC servers. These are cards with an INTeL-CPU and it's own RAM. These allow you to run Netware or Windows directly from virtual disk files on the AS/400 disks. Even if not in use, these cards draw a good deal of power. E. g. 2850-011-Adapter: Pentium II@333MHz with 128 MB RAM sucks about 20 W extra power from the power supply.
The low end model 9401-150 is more on the 60 W-end whereas a full blown 9406-S20 with two full disk cages is more on the 300 W-end.
Oh, and: The AS/400 greatly benefits from having many disks. Data is cut into pieces and scattered over all available disks, just like RAID 0.
Boot time
Okay, you want to have a big box. You plan to boot when you decide to tinker around and shut it down when you're done. Drawback is that those machines take awful long to boot. I'm talking about 5..15 Minutes or more, if the system was powered off without proper shutdown. Keep in mind that you probably don't tinker around as much as you wanted, because booting the box for just a short test isn't worthwhile.
Shutdown also takes several minutes.
Besides that, AS/400s usually can be tasked to power up and down to certain times on certain days.
Boot and shutdown are somewhat I/O intensive tasks. More disks make the box boot a bit faster.
Noise Level
Most machines are surprisingly silent when initially powered on: Only the fans rotate. Disks will be started one by one during the boot sequence.
The more disks, the more noise. The more disks, the more performance you gain.
The faster the disks, the more noise. The faster the disks, the more performance you gain.
Many disks of around the 2000s are slightly out of rotational balance, which is not a problem. But these usually produce audible hum between around 100..300 Hertz, depending on rotational speed of the disks in question. Especially when the outer case of the box resonates, this could multiply the noise level. Add the audible beat effect resulting from tiny differences in rotational speed and you get a hum swelling louder and quieter.
From my experience, this hum is way more annoying than the sole noise from disks just spinning with a slight increase when the disk actually positions its heads to read or write data.
If you're lucky you can tuck away the box in the basement.
Another considerable option is to buy adhesive bitumen mats and stick these to the inside of the case. This usually makes a huge difference.
I have a 9401-150 with three 2 GB disks with a slow spindle speed. The hum was barely audible but after applying bitumen mats to the case, the box is now so quiet, I could run it in the living room with only slight disturbance. The box feels much slower than another 9401-150 with four 8 GB 7200 RPM disks, though.
Accessories
Often, companies throw away documentation, license keys, proof of ownership, OS CDs and other stuff prior to the disposal of the machine itself. The machines usually are heavy and as long as the occupied space is not needed, they tend to stay.
Hard Disks are often formatted or even removed and scrapped onsite to prevent data leaks. This transforms the machine in question into a nearly useless blob of mainly steel.
OS install CD images can be acquired by asking nicely in proper USENET groups or web based forums revolving around AS/400. But without license keys, you have 72 days from installation until the machine finally refuses to boot. Or to provide proper license keys which stops this timer. The other option is to reinstall the OS. The LIC-keys are dependent on model and serial number and possibly other factors. So, it's not as easy as searching for s3r14lz in h4ck3r'z sp4c3z.
Even if you manage to get a box and put in some SCSI disks, it just won't work. IBM utilizes disks with unusual sector size. So you need to buy expensive AS/400 compatible (used) hard disks to re-equip the box.
There are certain combinations of system type and OS version which just work without entering any license keys. One such combination is a 9401-150 with OS/400 V4R5M0.
Console
AS/400s usually don't have a keyboard connector nor a port for a VGA display. They lack a RS-232 port for attaching a serial terminal (or PC with terminal emulation software).
For the initial setup, troubleshooting and backup of the system a console is needed. This equals to a 5250 terminal from IBM or equivalents from other manufacturers. Most companies who had AS/400 still have at least one of these in the basement: Because a console is important.
Every machine has a so called twinax controller either build in or on a PCI card. The connector type is either DB-9F or larger at the box itself. Another needed accessory is the so called twinax brick, a heavy plastic box with multiple twinax connectors and a cable with a fitting plug for the attachment to the twinax controller in the AS/400.
Older (CISC) machines might have twinax plugs directly attached to their case.
The twinax connectors on the brick have numbers, starting from 0. The console terminal is (in part) determined by attaching it to connector 0.
Terminals were attached to the twinax cable with kind of a Y-adapter: A short piece of two cables having two twinax plugs on two ends and a DB-15 connector on the common end of the Y. The DB-15 is attached to the logic board of the terminal. The two twinax ports allowed to daisy-chain terminals on one common twinax cable.
Every twinax terminal has a primary address[1] and probably a secondary address. The console must have it's address set to 0.
Device id 0 on twinax port 0 defines the console.
One may check and/or change the terminal settings by powering off the terminal, pressing and holding the space bar on the keyboard and powering on the terminal. You'll be presented by a menu system for changing and viewing settings.
Terminals don't utilize flash memory for storing settings. Usually there is a battery soldered to the logic board to allow NVRAM to retain it's information. If terminals lose their settings when not being powered on, it's very likely that this battery is drained and should be exchanged before it starts to leak corrosive chemicals, destroying the logic board of the terminal.
Y2K issues
Very old machines (beige case, CISC CPU, pre 199x) usually run very old OS releases which aren't y2k-safe. One may chose to select a pastime year with a likewise mapping from weekday to date.
IBM states[2], Version 3 of OS/400 is „Y2k-enabled“ to different degrees in the minor releases of V3 with appropriate patches (PTFs) applied.
Space requirements
Depending on model, AS/400s can be huge. Keep this in mind when running for the fast but cheap box.
Also, console display and keyboard need space. They don't need to be physically attached all the time, though.
Recommendation
If asked for a precise recommendation, I'd say, a 9401-150, equipped with max. memory (192 MB) and four disks is nearly optimal:
- Small form factor,
- Comparatively low power consumption,
- No need for license keys,
- Reasonably fast.
Drawbacks include:
- Too slow for heavy usage of SQL in interactive applications,
- Attach to modern LANs through an ethernet card which runs at 10 Mbit/s only (2723 adapter) or 16 Mbit/s Token Ring (2724 adapter). Probably not a huge problem since the CPU is easily saturated by a single FTP transfer over TCP/IP. IP is a very resource hungry protocol. And we mostly will run terminal sessions which need only a tiny fraction of the seemingly tiny bandwidth. See also: Getting Data in and out of your AS/400,
- Maybe noisy, depending on the disks,
- Old machine: Was current around the 2000s.