For the second installment in our new Vintage Computer Series, we are going to look at the IBM AS/400 Advanced.

The IBM AS/400 Advanced 36

In addition to a lengthy gallery of pictures, I’m going to basically do a modern-day “review” of this ancient piece of crap fascinating piece of vintage computing, inadvertently serving a dual-purpose as documentation since IBM has since abandoned all support for this machine as a result of their remarketing strategy and end-of-life support limit.

(Click here to skip to the picture gallery)

The History

While I can’t be 100% certain of the date on this machine, I would ballpark it around the late 80′s to mid 90′s, with the mid 90′s at the very latest. The computer is technically within the “minicomputer” class, although I tend to inadvertently call it a “mainframe” in casual conversation for both simplicity and because, frankly, this machine doesn’t look very “mini” compared to the computers of today (and I don’t feel like explaining that to everyone that asks).

Either way, this thing is a beast. It stands nearly two feet tall, over two and a half feet deep, and a little over a foot wide. Lifting it onto the little table seen in the eBay-esque pictures was a spine-numbing (and finger-crushing) task in itself.

The name AS/400 was the first of three IBM would name the product line of machines using this technology: a little after the AS/400 was end-of-life’d by IBM support standards, the series was renamed “iSeries”, and would later be renamed in a similar manner to the current name of “System i”. Any attempt to locate documentation on this machine only leads to product pages for the current Series i minicomputers, and IBM phone support was simply a wild goose chase.

I don’t expect IBM to fully support this piece of machinery, I just wanted some documentation: seeing as how there is none, I plan on writing everything I know about the machine here in case somebody else might stumble across one of these and need it.

The Hardware

The hardware on this beast consists of an IBM POWER processor (model unknown), four sticks of RAM undetermined in size, and a plethora of input/output connections. These I/O boards are literally half the machine: there are six full-size expansion card slots on the back of it, and internally they are connected via two dedicated boards for communication with the processor/RAM board.

The three boards on the inside of the machine seem to be divided up by function: one for what would comprise of a modern-day north bridge, one for extensible input/output (south bridge), and one that ties them all together while holding extra peripherals such as the system clock, NVRAM, power connections and other miscellaneous internal connections like SCSI and the IDE-like connections used in the machine.

For storage, our unit (donated from a local business a few years back) came with three SCSI hard disks of unknown size, and a tape drive labeled as “8GB QIC”.

The front panel, whose function is further detailed below, is a collection of three LEDs (depicting power, I/O usage and terminal activity) and 8 seven-segment displays for IPL loading with user interaction via three plastic buttons below it (up, down, enter).

Dumb terminals are connected via a Twinax block with a proprietary parallel port-style connection, with two such connectors on the back (one on an I/O card in our model). The connection is simple: 8 channels (0 – 7), with two pins for each connection with the terminals connected in a proprietary bus topology with a very long maximum segment length.

The redundancy of the hardware is a prime example that this machine was made to last for life (err, until the end of IBM’s support, at least). There are two power supplies that daisy-chain together (unlike the Dell Poweredge types), leading me to believe that one of them houses an internal battery backup contributing to the overall weight of the machine.

Other redundant hardware includes the three (striped?) SCSI disks, and the hot-swappable I/O cards and power connectors. I joked to someone helping me move the thing that you’d have to bomb it to take it offline, and even at that it would be difficult because of the thick steel plates housing the internals. We’ve thus nicknamed it the “WOPR” in reference to the 1984 movie Wargames.

Software

This whole section will be updated in the future, because our Twinax terminal will be arriving in a day or so as of this writing. With the terminal, we will be able to directly interact with the operating system (although my AS/400 control language is rusty) and provide a better overview of the software running on this machine, in addition to discovering more hardware specs.

The “BIOS” of the machine is entirely user-directed. Reminiscent of a time where operating system software was loaded via punch card or rotary dial, the loading on this machine is done via the mentioned front panel (pictured in the gallery below), which comprises of three buttons and a series of 8 display segments.

The legend on the back of the (key-protected) panel’s door provides an overview of what the panel does: it provides user access to hardware functions pointed to in memory, most of which are 24-bytes long. These functions consist of everything from a simple lamp test to the execution of the first sectors of a designated storage device, e.g. one in-memory hardware function pointer (IPL) for the tape driver, one for SCSI location 1, and so on.

These IPLs (initial program loaders) provide the same hardware-based service employed by the BIOS/EFI of the modern PC architecture, and serves as a method of executing a loader program (bootloader) stored on a designated storage device within the machine, which will then go on to load and execute the operating system.

Last Notes

Just as a few final words on this amazing piece of big-iron computing history, while this isn’t the most extravagant piece of hardware we could write about (we don’t have a Mark II or UNIVAC laying around), I feel it has its place in history and deserves a dedicated story in our new Vintage Computer Series, especially as guide for others not familiar with its hardware.

The picture gallery below displays the best pictures we took of it (hosted by ImageShack, so our bandwidth doesn’t get obliterated again), and you may notice a few missing pieces: one of the front black plastic covers is missing, so you’ll notice the gray chassis visible in its place. Other than that, all of the other pieces we received with it are still connected, although we’re positive that there are other expansion cards providing extra services like networking and telephony.

Other connections not mentioned are two serial connections on the back, one labeled “UPS” (battery backup communication) on our model, with the other labeled “MI”. There are also some connections on the back (packaged as miniature modules connecting to larger expansion cards) that have a vast array of pins, and we couldn’t even begin to tell you what they are used for.

All in all, I’m simply amazed by this piece of hardware and feel lucky to work on it. I hope to get a better feel for what’s going on software-wise with it once our terminal comes in, and I’ll post a followup when that happens. For now, enjoy the pictures we took of this machine!

Picture Gallery

The IBM AS/400 Advanced

The Back I/O boards, with visible Twinax hub atop

A shot of the internals from one side; visible are the SCSI cables and internal power connections

A closeup of the power and SCSI connections used by the drives

A shot of the back with the expansion card taken out. Shown are the proprietary input/output connections used by the cards.

A shot of the back of an expansion card. Visible is the proprietary I/O connection, and a few onboard chips.

An expansion card shown with a stapler on top for size comparison. This card hosts a parallel port used for Twinax hub/terminal communication.

A "filler card" used to fill up/keep dust out of input/output connections not in use.

Another shot of the back, with all cards (and fillers) in place. Note the redundant power supplies at the bottom.

A SCSI drive taken from the machine. Note the size of the chips, and the next picture shows a size comparison.

A size comparison of the AS/400's SCSI drive next to a standard IDE hard drive and (Cisco) compact flash card.

A shot of the AS/400's processing board. You can see the RAM, heatsink-covered processor, the (giant) onboard 8-bit speaker, and some of the I/O board.

The AS/400's SCSI drives. Also visible is the tape drive, and the NVRAM chips of the I/O board are also visible.

I hope somebody else finds this interesting or helpful, as I could sure have utilized some documentation while first figuring this piece of equipment out. And for you AS/400 veterans, Googlers, or just casual readers, I hope you enjoyed this not-so-little piece of bigiron computing history as much as we did!