More Than You Ever Wanted to know about Standard (and even some stuff on non-standard) PC Chassis from the 1980's-1990's
Probably one of the most looked at and talked about, but technically neglected parts of vintage PCs is the chassis. PC Chassis is basically just a bent up metal box, usually constructed to some kind of "standard" such as "XT" "AT" "Baby-AT", or later on "ATX" "mATX" (Micro ATX), and then you had two sub-standards LPX (or "Pizza Box") and "NLX" used later on for low-profile systems. There are no standard chassis designs for Laptops.
Form Factors Explained
Standard IBM Compatible PC's are built to what is called a "Form Factor", or a set design that allows standardized parts to be interchangeable with each other. For early IBM Compatibles (Pre-Pentium), this was XT, AT, and Baby-AT, with a sub-standard LPX sometimes being mentioned as well. The main distinction between these designs was mostly in the power supplies, the rest of it was pretty interchangeable, except for full sized AT motherboard into a Baby AT or XT case (those shared the same motherboard size restrictions which were smaller than full AT).

XT FORM FACTOR - The "XT" Form factor is derived from the IBM Personal Computer XT released in 1983. This design is a roughly 14"x22"x7.5" metal box with a plastic front bezel. The top cover is typically attached with 3-5 screws from the back surrounding the perimeter of the back of the case. It can use XT and Baby AT style motherboards. Typically these cases have 2 full height 5.25" drive bays that can be split in half into a total of 4 half-height 5.25" drive bays. Earlier clone cases had all-external drive bays and mimiced the look of the IBM PC XT, while later models, such as those made by Steelcase for DTK and DFI, concealed the middle two bays to mimic the look of an IBM PC AT in a smaller size. The biggest defining difference is the power supply, a 11.5" wide, 5.25" long, 5.25" tall box with a fan on TOP inside the case, with a louvered vent in the back for air to pass out of the chassis from, and a big, black, bezel with a red or black clicky power switch in it. Earlier XT Form factor cases have no control bezel. There's also a subset of these on the clone side called "Flip-Top" cases that open like a car hood, allowing easy access to all of the components inside the chassis. The power supplies in an XT range from a measley 63.5" watt of the original IBM PC, all the way to a whooping 300 Watts for some late "Turbo XT" builds that have a lot of stuff under the hood.

(FULL SIZE) AT FORM FACTOR - Again, taken from an IBM PC Model, in this case the 1984 IBM Personal Computer AT 5170. These chassis are about 14"x24"x8" in size, and can accomodate the now very rare and oddball "Full AT" Sized motherboard. These motherboards measured about 13.5"x13.5" in size, as can be told by the nearly centeral location of the keyboard connector after the ISA slots. Full AT motherboards are pretty much only found in the 286 and 386 era and died off in favor of the XT-Sized "Baby AT" motherboards, though some 486 and later examples exist designed for a "Full AT Tower"program psu calculator using html adaptation in the early 90's. The Power Supplies range from a 8x8x8 metal box to an 8x12x8 metal box, with and without the clicky paddle switch on the right rear corner. Tower versions had a cable like Baby AT. The older desktop Full AT chassis were mostly used on 286, 386, and very very early 486 PC clones, and a lot of them look like an actual IBM AT, at least 75% of the way there. There were some variations, including one GEM Computer Products used that looked like an original Compaq Deskpro/286/386 chassis from the outside. ATs typically sit around the 200-250 Watt PSU category, with some going as high as 500 Watts for the later "Server Tower" variants that started to show up in the early 1990's.

BABY AT FORM FACTOR - Baby AT is really just XT with a new power supply design. The same motherboards fit in the same connecting holes, and it has the same eight slot provisions in the back. These cases come in the wide range of formats like we have today, ranging from fake "LPX" lookalikes, all the way to ginormous full-towers that can accomodate a full AT motherboard. The two most common in the late 80's and early-mid 1990's were the Desktop Baby-AT, and the mini-Tower baby AT. These cases were roughly about 14"x14"x10", with the tower sitting instead of 14" wide and 10" tall, at 10" wide and 14" tall. These cases were the first to have dedicated internal and external bays for 3.5" half-height devices, and the power supply uses the same, familiar, ATX measurements we still use today: 150mmx86mmx140mm in size. They came in an amazing array of colors and styles including the classic "beige" that yellows as it gets older that many seek today, in boxy 80's industrial-like designs with lots of right angles, vents, and LED lights, to black and rounded cases that look more like something you would have seen circa 2005. Some common case manufacturers included: Kingspao, Antec, SteelCase, and Songcheer.

LPX FORM FACTOR EXPLAINED (PIZZA BOX) - The "Pizza Box" computer design originated with another IBM series, the IBM Personal System/2 Model 30. The "Pizza Box" design became extremely popular in consumer and regular user-class workstations in the late 80's till the mid-late 1990's. These devices had a motherboard that used VLSI (Very Large Scale Integration) to integrat the graphics card, serial ports, parallel port, PS/2 keyboard/mouse ports, and even some other stuff (Ethernet, Sound) onto the motherboard. Instead of 6-8 ISA/PCI/VLB/EISA slots on the motherboard, you had one big, super-elongated slot, and then stuck into that was a Riser Card where expansion cards would fan out from the sides, allowing for a low profile granting the whole "Pizza Box" look of the computer. These used the same 150x86x140mm power supply style as Baby-AT complete with the same power connectors used since the beginning of the PC (P8, P9). However, it was only a "quasi-standard" or "sub-standard" because no standard was set for the distance of the riser card from the slots, and no limits or standards were set for how many slots at what height were allowed. Also, some manufacturers took weird approaches to the power supply, such as Packard Bell with their "poking stick" style power switch design that poked a button INSIDE the power supply using a plastic rod run from the front of the case, to even some soft on/off setups similar to those found in ATX later on, such as that found on the IBM Personal Computer 330/350 series.

ATX, mATX, NLX, and SFX FORM FACTORS - ATX is a form factor that started to appear en-masse around 1996 or so. It's basically the same as Baby AT, except the motherboard has been turned on it's side, the number of slots have been reduced to 5 or less, and the VLSI part of LPX has been applied to a large "I/O SHield" in the back of the case where all the ports are located. It also did away with the hard on/off switch that turned off mains power from the PSU, favoring for a soft on/off switch that went through the motherboard, keeping the computer in a "standby" state when not "on". Also, none of these cases have turbo switches, and often, especially later on, these cases had the power switch hidden inside a vent hole to be pressed with a paper clip, such as the popular chassis made by InWin and Antec at the time. Micro ATX shortened the motherboard a bit and removed space for 2 slots, usually limiting slots to 3x. What's interesting is mATX, ATX, and even in some cases, Baby-AT/XT boards will fit in a full ATX chassis, with some even having special I/O shileds to allow for that, even shipping with a power switch that allows for AT PSUs. mATX cannot accomodate this unfortunatley. SFX is the same as mATX but uses a special, smaller, PSU that looks more like something found in an old IBM PS/2. NLX is an ATX-ish based update to LPX, and very rarelyh used in OEM systems. in the 20 years I've been in I.T., I've only seen ONE NLX machine, and that was a circa 2000 Hewlett Packard I did a R&R on in 2004.

Typically, an IBM COmpatible from 1981-present contains at least a power switch/button. However, there are multiple different things added to the front/back of the case that you might have seen and wondered what their purpose are and why/why not people have used them (I know, it's not grammatically correct, but I want to keep the "down home" feel of this page dagnabbit!).

Power Switch - Power Switches are represented by one of two universal symbols. Originally they used a |/O symbol with "|" meaning "On" and "0" meaning "Off". Later the International Symbol for power - a circle with a line coming up the bottom, started to become more commonplate in the 1990's. On the oldest machines (AT, XT), the power switch is located on the right rear corner of the case, usually in a funnel-like black indent, while later on, this was moved to the front of the case behind a stylized bezel, with a hardware power switch attached to a 2 or 4 conductor wire. When ATX came around, this switch was changed to a momentary, normally off, push button, that connected to a 2-pin header on the motherboard, which is how it has remained ever since.

Reset Switch - The Reset Switch was a development created because sometimes a machine could become so hung, not even CTRL+ALT+DEL could bring it back from it's confused and stuck state. So here was a hardware button you could press to hard-reboot the system and bring it back to attention. This is basically just a momentary, normally off push-button on the face of the case, that goes to a 2-pin header on the motherboard often marked "reset" or "rst". When pressed, it does not properly shut down the computer, but rather, acts as if you flipped the power switch on your outlet strip and flipped it back on, even on modern systems (hence why not a lot of modern systems have this switch anymore). Some modern systems do have one, as well as some newer ATX cases, however, it usually has a "pinhole" to keep someone from either resetting the machine by mistake without properly shutting down, or deliberatly messing up the system because Windows requires a proper startup-shutdown cycle to prevent hurting itself.

Turbo Switch - The Turbo Switch was introduced with the IBM PErsonal Computer AT in 1984, and heavily copied up until when the Pentium started to become commonplace circa 1995 or so. What the Turbo Switch's original intention was, was not really as a "turbo", but rather a "slow-down" switch. When you pressed it, the PC would slow down, and the accompanying (usually Amber) LED light next to the symbol/"Turbo" would turn off, putting your machine in a mode more compatible with older software. In the case of 286 and 386 SX systems, this could get slow enough to emulate an original IBM PC, but with later, faster 386 DX systems and most 486 systems, it was a moot point because the system was too fast to slow down enough to run at the proper speed for ancient software, so it was omitted starting around 1994 or so. Turbo Switches come in two varieties, one is a 2 pin switch with a 2 pin header intended for cases without a digital readout, the other one is a three pin affair that connects to a digital readout board that displays 2 different sets of eight segment display characters depending on the status of the turbo switch.

Power LED (usually GREEN) - THis was usually a green LED light on the front of the case that lit up when the PC was on, starting around the Turbo XT/early-mid 286 era. It would sit next to a label that was either a lightbulb, or said "Power" next to it. Power LEDs are still found on modern PC cases, however, these days they are usually white or blue, instead of green. Green was a standard on vintage PC's (Pentium D on back). Usually these connected to two pins on a three pin header, and sometimes it was a 5 pin connector with the keylock switch attached to it. Either way, Green's the universal color, and sometimes they can be red as well, such as on Tandy products and Pre-Turbo XT clone products.

Turbo LED (Usually Amber) - This Amber LED would appear next to a poof of smoke, the word "Turbo", or some other symbol (a racecar perhaps) to indicate that the computer was running at full throttle (IE, the MHZ speed listed on the CPU). It first appeared on "Turbo XT Clones" and the IBM PErsonal Computer AT, and was a standard piece on computers, regardless of if it had a turbo-switch or not, up until the Pentium era. Some computers that did not have a turbo switch on the case instead used a key combination on the keyboard to turn Turbo on and off. Usually something like CTRL+ALT+"+" or CTRL+ALT+"/". Contrary to common belief though, these did not get used all that much anyway. Most of the time these connected to the motherboard via 2-pin header where it showed TBLED, though systems that had both a Turbo LED and a digital readout had the LED pass-through the Digital Readout Module.

H.D.D. LED (Usually Red) - This LED light would appear next to the word "Hard Disk" "Busy" "H.D.D." or something looking like a cartoon tin can (cylinder). It would normally be off except when the HDD was reading/writing. The HDD LED did not really take off until the IBM AT when the idea of a fully internal "Hard Disk" or "Winchester" drive became the norm. Prior to that, Hard Disks on PC's had a black or gray faceplate with a little red or green LED on it that told you when it was reading from or writing to the Hard Drive. HDD LED lights actually hung around for a long time until Solid State storage became the norm. The 2014 Dell Laptop I'm writing this on has a HDD LED even. The HDD LED was very useful to tell if the machine was actually doing something, or if it was hung.

KeyLock - The Keylock, usually a Chicago barrel style lock, served one or two purposes on a PC case. Most major OEMS, IBM and Compaq in particular, had case keylocks that actually locked the case shut and even in a lot of cases, triggered a switch in case someone decided to destroy the computer case to get inside and steal the components inside. But on most clones, all the keylock did was act as a primitive form of "Login" of sorts. Basically, it's lunchtime, you have a major, important spreadsheet or document on screen, and you don't want anyone to mess with you pull out your keylock keys, literally "lock" your computer, and nobody can mess with it because the keyboard port is disabled. Hwoever, as Windows took over, this did nothing for the mouse, so it provided almost no security anyway (especially if someone got their hands on the keymap program, lol). So slowly it lost favor over the Windows Login Prompt as the 1990's continued on and mouseless DOS systems joined the 80's in obsolescence. These are usually a 2 pin header that attaches somewhere near the power LED, if not integrated into the power LED's jumper block.

DIGITAL READOUTS - Starting towards the era of the early 486, and the 386 DX-40, we started to see some Baby-AT cases come with a "Digital REadout" in front, which was basically just a 2-3 character series of 8-segment displays, configured via a series of Jumpers on the back. The b.s. story you got back in the day was that it read the cPU speed off the motherboard, but in actuality, you could make that thing say anything you wanted whether that was "100" and "33", "Hi" and "Lo", or "666" and "777". That said, there WERE some rare and few computers that had digital readouts that actually did useful stuff - such as those found on Dells, Amdek/Wyse, and some other systems, but most of them were just a pile of jumpers, eight segment displays, and maybe a resistor and a capacitor.

Front Keyboard Ports - In some rare cases on standard XT/AT systems, system's makers would relocate the keyboard port to the front of the chassis. I have seen at least 2-3 types of PC Desktop chassis that allowed for this, including Flip-Top XT Chassis, a GEM Computer Products 386 DX-20 that did it to copy the looks of hte original Compaq Deskpro 8086/286/386, and some "Steelcase" mini-tower chassis from the late 80's/early 90's including the one my sister's AMT 386 was in had a provision for. Basically, all these were, was a DIN-5 extention cable running to a DIN-5 port in the front of the case. It's actually kind of a rare feature to see. Today it's totally un-needed, because you almost always have 2-4 front USB ports on a desktop machine regardless of form factor.

DB-port Punch-outs/Cutouts/Plates - You've probably seen, if you've seen a vintage PC system, a series of 4-12 plates in the back of the system that are roughly the shape of serial, parallel, and in rare cases a game port and/or IBM PS/2 port hole (for a mouse). These were for those "Multi I/O" cards you could buy that came with a second ISA slot cover with 2-3 ports in it, so you could relocate those to the back of the case, and utilize your other expansion slots rather than take up a unused slot with a metal plate with some DB-9 and DB-25 connectors on it. Even later builds could make use of these as they had built-in game ports, PS/2 mouse ports, USB ports that could fit into these sockets, and so on. These are a very often overlooked and ignored feature of vintage PC chassis.

Digital Readout Diagram
Here's an old Digital Readout Jumpering Diagram from my AMT 486 computer I had years ago. I made this for the original Creeping Network website but never finished putting everything together. It also includes standard 4-wire power switch wiring for AT compatible computers.

Laptops - Semi-Proprietary Stuff
By now you're probably wondering "hey, what about the laptops?". Well, portable computers were a bit of a weird thing in that, unlike the regular desktop machines, which more standard as they went along, laptops got LESS standard as they went along.

The earliest IBM PC Compatible portable of much renown was the Compaq Portable released in 1982. While not 100% standard, it was more standard than the laptops we would see at the turn of the 1990's. It had regular 8-bit ISA Slot expansion, a regular, standard DIP CPU, Math Co-Processor socket, and Memory like a regular desktop. Even the cards themselves were mostly standard, with the custom Compaq graphics card being able to drive the small 10" internal green-monochrome CRT as well as an external Monochrome or color RGB monitor. The computer was about the size of a sewing machine case and weight about as much (or maybe more) too, but was built like a brick outhouse! It was also the first 100% IBM Compatible clone of the PC.

Not to be outdone, many other companies made their own standard-ish portable "luggable" PCs including IBM themselves made the "Portable PC" a year later, using a standard IBM PC XT/Industrial PC motherboard, and all standard ports - making it pretty much 100% upgradable with whatever aftermarket tech you could jam in there up to a early Pentium (though I can't imagine anyone being so joyful about a MONOCHROME Pentium system). Sanyo made the first fully color portable with the Sanyo MBC-775 luggable XT Clone.

But the thing was these behemoths were not usable while on the airplane, or train, or in the back of a limosine. You STILL needed a regular mains power outlet to run the machine. The intent was TRAVELING WITH the machine, not using it WHILE you traveled. They also were heavy, as heavy as, or even heavier than some Desktop computers.

Slightly less as cumbersome came the "Lunchbox Luggables" - these were a mid-late 1980's invention, kinda' spearheaded by Compaq again, including the Compaq Portable III, Compaq Portable 386, Compaq Portable 486, and the IBM Portable P70 386. Still the same idea as the original Luggables, desktop level parts and expansion for full Desktop performance, but small enough to lug around, and quite a bit smaller than the old ones which weighed 45LBS and were the size of a Utility Television (with a screen 1/4 the size). The made use of new Gas Plasma and LCD Screen technologies. This really shows the beginning of computer design in the late 1980's where we saw a split between performance and portability. These machines were aimed at power users who needed a fast CPU, a co-processor, high resolution graphics, in a portable (enough) machine to drag around with them. Like Travelling STEM people.

Along side these came the evolution of what became the now standard "Clamshell Laptop" design. There's a bunch of these that came out around the same time including designs by NEC in their Prospeed, Multispeed, and UltraLite platforms, IBM with their PS/Note and later Thinkpad systems, Zenith's SuperSport series, Compaq's LTE 286, and of course GrID's ruggedized designs often used by Civil Services such as Ambulance and Law Enforcement.

These early Clamshell Laptops were Tiny by the day's standards, but look like friggin lead bricks by today's standards, some were as big as a electric typewriter from the same time period. The earliest ones typically had either gas plasma, or more often than not, a blue/white STN LCD Display with CFL Backlights. Most of the earliest ones like the NEC Multi and Prospeed machines, Zenith's early SuperSports, and Samsung and Toshiba's early offerings, had keyboards that had the same size of keys and key mechanisms as a full sized desktop PC. They all ran on large, wimpy, NiCad batteries, some of which could only eek out 15 minutes of Battery Life, and some of which could hit as high as an hour with the contrast turned down, judicious use of various power saving bits (turning off the hard disk, turning off other devices, turning the CPU Speed down), and careful charging behaviors healthy for the battery.

I mentioned the NEC UltraLite, which is said to be one of the most influential laptops in history. Here in the time of behemoth laptops that barely counted as laptops, let alone portable, and weighed as much as a heavier Gibson Les Paul guitar - circa 1988 - NEC released a laptop that was sub-5LB, had a size reduced keyboard, used (Battery-backed) solid-state storage, an okay LCD, and could run for 8 hours on a single charge!

But with all this reduced size, to keep up, all manufacturers, even NEC themselves, had to resort to making things standard on desktop PCs: Memory, Motherboards, Expansion Cards, Screens, Keyboards, and later Pointing Devices, and even certain on-board additions such as networking or Modems PROPRIETARY and only capable of working with a particular system or a particular product line from a particular time period. A lot of these systems even barred the user from using standard CPUs from desktop machines because to reduce the size further and save on power, they had to use lower-voltage, surface-mount soldered CPUs, such as the 486 SL or 386 SX to reach a point hte public would be willing to spend $1500-6000 on a portable computer they could use while on the go off of battery power.

That said, some standards TRIED to be established during the time. The Personal Computer Memory Card International Association - PCMCIA - created their own standard line of expansion cards for PC's. Starting with PCMCIA Type I in 1989, meant merely for memory cards. Eventually, by about 1992 or so, they started to come up with Type II and Type III which allowed for a myrad of standard expansion devices for laptops besides just memory cards, such as Modems, SCSI Cards, Sound Cards, Network CArds, Video Capture cards. These can be almost thought of as an "ISA Bus for (386/486) Laptops". It was later superceded by Cardbus (32-bit) by the mid 1990's, and Express Cards by the turn of the century. Today, we use USB in lieu of these technologies, since USB can do the same thing that required a specialized bus back then for acceptable speed.

Hard Disks started to get standard in the IDE era, the modern 2.5" Form factor actually started back then as well. However, most manufacturers had one little itty bitty problem, they tried to bolster user servicability on the go, and collect bigger income from goofey little "carriers" or "Caddies" for their hard disks, sometimes even given weird little names like "VersaPak" as NEC Did for their Versa series laptops (Toshiba, Compaq, Samsung, NanTan, and others did this as well). This meant that while the 44 pin IDE header was standard, it required the drive to have some special connector at the other end to attach to the motherboard. This causes us a LOT of problems recieving Vintage laptop computers from e-bay and elsewhere that are missing these caddies, which is another caveat.

But as this is case stuff - let's talk a little bit about laptop cases with regards to durability. The earliest laptop computers of this style had thicker plastic, heavier hinges, and were a bit more durably designed, with weak links mostly being in the cable connections for the power supply or the screen's internal cabling (due to all the flexing the screen around opening/closing and adjusting the screen).

As the early 1990's came, more and more parts were made of lighter plastics, and it seemed the tech industry at the time was really getting into a "Brominated" plastic phase. Apple, Lenovo, and NEC are NOTORIOUS for this (as is Nintendo). This plastic was generally marketed as "flame retardant" and over time, the nitrates in the plastic from the bromination come to the surface and evaporate, leaving holes in the structure, yellowing the case more than usual, and causing the plastic to become very hard and brittle, like a Townhouse Cracker. This paired with the stiffening of the hinges as the lubricants break down and dust and dirt clings into the lubricants inside and gums up the hinges causes a lot of catastrophic hinge failures on this era of laptops.

There's also a lot of power-supply related caveats with laptops from the 1990's on back as well.

First off, nobody had a standard laptop connector back then, and in those days, it was even WORSE. You had some companies using regular barrel jacks like guitar pedals and neck massagers, or your 8-bit NES did, but you had others with all sorts of weird connectors ranging from 4-12 pin DIN connectors, proprietary molded things like NEC, IBM, and Compaq were using. This can make finding power supplies for more obscure devices a difficult proposition with no part numbers or general information other than the voltage to go off of. The power supply might have 19vdc, but it might be pushing only 12vdc on one pin, -12vdc on one pin, +5vdc on one pin, and -5vdc on one pin - all split off a 19vdc source, or it could be pushing 19vdc to all 4 pins and splitting it off inside the laptop itself - maybe all with different current ratings? Maybe the 19v is split off in a weird way. You have to have something to go on to reverse engineer something like this and get these old laptops working.

Another problem is batteries. The earliest clamshells did not even have batteries, and later they started to use specialty NiCad batteries that were usually a collection of "C" or "D" sized cells put together. This lasted into the early 1990's, where the chemistry switched to Nickel Metal Hydride (NiMH). As we were having another big environmental focus in the early 1990's to save the planet, NiMH was a GREAT battery technology because it was less as harmful to the environment than NiCad or the Lithium Ion Batteries that replaced them (as well as far less dangerous than LiIon). Lithium Ion started to take over around 1995 or so on certain laptop computers such as IBM's 755 series and the later NEC Versa machines.

A lot of people remove our batteries from our vintage laptops because they begin to leak and corrode internal components if not addressed or properly taken care of (or exercised if they still work - bleieve it or not, I've encountered quite a few 15-20-30 year old Laptop batteries that still worked, the oldest being the NiCad in my BSi/NanTan FMA3500C Laptop - which was REALLY Surprising).

But some loonies, like myself, like to experiment with batteries and power on these old machines, because the draw was, once-upon-a-time at least, that they were supposed to b e PORTALBLE, as in used without an electrical socket tying it to a specific location.