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There were personnel computers before the IBM 5150 but the 5150 is the computer that solidified what an IBM compatible PC would be. The 5150 featured an x86 processor, internal slots for various upgrade cards and was primarily intended to run off of PC-DOS / Microsoft MS-DOS operating system, all things we would learn to associate with the future IBM PC compatible market. The IBM 5150 was released in 1981 and was primarily intended as a machine for serious business tasks but was certainly capable of playing games and performing other non business functions.

The overall construction of the 5150 is extremely sturdy with a heavy metal case. The face of the case features no buttons or LEDs that we expect from later PCs and just features a stylish IBM PC badge, some vents and dual full height drive bays. The 5150 was sold in a few configurations including dual and single floppy drive variations as well as a version with no drives at all.

The dual full height bays commonly housed one or two 160k/360k (single/double sided) floppy disk drives. You can add two half height drives into these bays though this will require some means to secure the mounting as the bays are designed only to secure full height drives.

The power button is located on the left rear side of the 5150 case and uses a large on/off switch.

A locking mechanism was sold by IBM which one would place over the power switch which allowed the PC to only be turned on with the use of a key though I believe this also worked with XT and AT models as well.

Lets take a quick look at the rear of the case.

On the left side we have one female and one male power port. the male connector uses a standard three prong power cable with the female connector intended for a monitor to to plug into. To the right of the plugs we have a large round vent for the power supply followed by a keyboard and cassette connector. On my PC these ports are conveniently labeled.

The original keyboard for the IBM 5150 is the model F.

Model F keyboard

The model F is similar to the later model M in that it is very well built and does feature “clicky” keys. As you can see above the function keys are located to the left and there is no space between the num pad and the rest of the keys. This is a PC/XT class keyboard and will not work on later AT class machines.

The cassette port located next to the keyboard port was rarely used on the 5150 though I suppose if one had purchased a variation without any disk drives this would have been the expected method of data transfer. Finally we have five slots for adding expansion various cards.

Before opening this case up and looking inside lets take a quick look at the monitor.

The intended monitor for the 5150 was the IBM 5151 green monochrome monitor. Being mostly intended as a machine for office use where sharp text took priority over color, although IBM did release a color CGA and EGA monitor with very similar styling. The 5151 monitor gives a very nice and sharp monochrome image and is also surprisingly light compared to the general heft of the 5150. The two dials are for controlling brightness and contrast.

Unfortunately the two power cords on the 5151 are hard wired to the monitor itself. One cord is a 9-pin connector to connect to a monochrome video card with the other being the power connector intended for connecting to the female plug on the 5150’s power supply. There is no power button on the 5151 as the monitor was intended to power on with the 5150.

OK, now lets take a look at the inside of our 5150.

Take note that I have upgraded the power supply in these images to a 130w power supply in order to accommodate a possible hard drive. The stock power supply in the 5150 is a fairly anemic 63w supply and may not supply enough power if a hard drive is added.

There were two motherboard versions released for the 5150 depending on when it was manufactured. Earlier models used the 16kb-64kb boards which only were capable of supplying a maximum of 64kb of RAM on the board’s RAM sockets. My 5150 uses the later 64kb-256kb motherboard indicating a total of 256kb of RAM could be installed on board.

1 ) CPU – The CPU is the classic 8088 running at 4.77MHz. This was a cost saving measure as the 16-bit 8086 would have been faster but more expensive. Keep in mind that the NEC V20 which offered a slight speed boost over the 8088 was a fairly common upgrade on these machines.

1.5 ) math copro – Located alongside the CPU socket is the FPU socket for adding an 8087 math co-processor if desired.

2 ) RAM – My PC has been upgraded to the full 256kb of memory. Notice how the first row of memory is directly soldered to the motherboard while the following three rows are socketed.

3 ) PC Speaker – The 5150 uses a real PC speaker located on the far side of the case.

4) Switches – Two switch blocks located on the motherboard are used for setting things such as installed memory, type of video card installed ect… switch settings as well as a large amount of other information on the 5150 and other IBM PCs can be found here.

Lets take a look at the various expansion cards I have installed in my 5150.

Unlike later IBM PC compatibles which upped the standard expansion slot count to eight the 5150 only sports five 8-bit ISA slots. This can be a little limiting considering there is virtually nothing built in as far as video and I/O goes as well as the fact that your going to most likely be losing one ISA slot right from the start to a floppy drive controller card.

This is the standard IBM floppy controller. It features an external floppy port and when paired with the 5150 can support up to four floppy drives. Drives connect via the edge connector on the rear of the card. This card is currently running my dual 160k/360k drives but is also capable of supporting 720k 3 1/2 inch floppy drives.

Next up of my currently installed cards we have the monochrome video / printer card.

The IBM monochrome monitor card (MDA card) is designed to connect to the 5151 monochrome monitor and you will usually find this card installed in almost all 5150’s. The MDA card is not capable of displaying pixel graphics but only characters thus making it largely unsuitable for games but great for business which mainly benefited from having a sharp text display. There are games like Rogue which can be played on an MDA monitor since it only uses text and characters for graphics. Thankfully IBM understood the situation with limited expansion ports so the IBM MDA card also included a printer port.

An option even better then the IBM monochrome card would be a Hercules card or Hercules compatible card. These cards also worked with a monochrome monitor and featured a parallel port but also had the added benefit of being able to display graphics on a monochrome monitor for games which supported Hercules mode and with a small program even emulate CGA graphics in monochrome.

Thankfully you could also install a CGA card (as well as an EGA or VGA card) in the 5150.

There are a few revisions of this card from IBM with minor differences but I am using a later revision here. Although you can install a EGA and even some VGA cards in the 5150 I find the machine lacks enough power and RAM to properly run those sorts of games and is best suited for playing CGA titles. There are also a number of later more advanced CGA cards from companies like ATI which offer more display modes in a smaller form factor but I was trying to keep things more or less IBM and early 80s with this build.

Most commonly CGA offers games to be played with four colors from just a few palettes. Black, Cyan, magenta, white is the palette most associated with CGA though there are other palette options.

The IBM CGA card also offers a composite out for connecting to a standard TV. This produces a less sharp image then CGA on a computer monitor but techniques like dithering can be used to blend colors and create an image resembling EGA in some cases.

You also have the option, like I have done with my 5150, of installing dual video cards. I currently have both a MDA and CGA card installed. You can switch back and forth between MDA and CGA monitors with a DOS command MODE CO40 for CGA 40 column mode, MODE CO80 for CGA 80 column mode and MODE MONO for the monochrome display in 80 column mode.

The final card I have installed is an AST MegaPlus II card.

multi function cards like the MegaPlus II and the AST SixPack Plus were fairly common for the IBM 5150. The lack of expansion slots gave an opportunity for third parties to step in and create expansion cards which incorporated several useful features into one card. The MegaPlus II adds a real time clock, up to 512kb of memory to bring your 5150 up to 640kb, a serial port as well as multiple headers for daughterboard expansions.

Adding a hard drive / 720kb floppy drive

I kept my 5150 fairly stock and period correct but for some extra quality of life adding a hard drive and 720kb floppy drive is fairly simple.

The first issue you’re going to have with adding two half height drives is that the bays were only designed to securely mount a single full height drive as we can see in the image below.

Any upper drive would have no points to mount to. Thankfully there are some solutions as mounting plates were made to allow the use of dual half height drives. Theoretically I suppose if you had some sheet metal and tools you could create your own mounting plates. Below is a mounting plate I used, unfortunately it has no labeling so I’m not sure if it was homemade or part of some official kit.

If you do not have a mounting plate I found improvising works just as well though may it may not look as eloquent of a solution. I was able to position a mounting rail from a random PC diagonally and use it as a fairly sturdy mounting solution.

Once the mounting situation has been taken care of its time to well….mount the drives. Mounting the 3 1/2 720kb is fairly simple as even the stock IBM floppy controller will support it. You just either need a cable with the correct connectors or install a pin to edge connector adapter on your 720kb drive and it should run just fine. Newer 1.44mb drives will also work as 720kb drives without issue.

Installing a hard drive is a little trickier as the stock power supply is under powered for the task and the 5150 was not initially designed with a hard drive in mind as IBM never offered a hard drive as an option although later it did offer a 5161 expansion unit which did house a hard drive but which was the size of the entire 5150. Your first task is to upgrade the power supply with a beefier one. I upgraded mine to a 130w supply.

If you want to be more period correct you will want a MFM or RLL hard drive controller. I used a WD controller as well as an ST-225 20MB drive which worked without issue for me.

If your not trying to be period correct your best bet would probably be an XT-IDE controller with a CF card as these draw much less power then period drives and offer much faster speeds and reliability.

A friend once asked me why I would want a 5150 and proceeded to ask me if I “wanted to emulate being a 1980s office worker”. This comment is actually pretty fair since the 5150 is first and foremost a business machine. You certainly can play games on it and with a little work upgrade it well for this purpose but in truth there are many better options if you’re looking for an early 80’s 4.77MHz niche machine. The weak power supply and limit of five expansion slots does not do the 5150 any favors. If you want an early 80’s 8088 based machine find or build a nice machine with eight slots a turbo button and 640kb of memory built in.

On the other hand as a collector of vintage PC hardware the 5150 is a no brainer, it needs to be in your collection. The 5150 is iconic and set the stage for all IBM PC compatibles for decades to come.

There’s just something about an IBM machine. After the PS/1 and PS/2 line IBM continued within the consumer PC market with a line simply known as the IBM PC line. This line of PC’s was sold roughly from 1994 to 2000 and consisted of many models from mid range 486 CPU’s to Pentium III’s. There isn’t anything particularly special about the IBM PC line as they don’t do anything necessarily new outside of a few uncommon design choices though I have to say I’ve always loved the look of the desktop cases within the line. In this article we are going to look at the 300PL type 6562…..sounds like a designation for a WWII Japanese tank.

ibm300pl1

I’ve just always liked the look of these desktops. Kind of unique look that mixes more modern style (late 90’s and 200’s) with older (80’s early 90’s). The only thing I really don’t care for is the plastic case seems pretty fragile in parts and mine received a fair amount of damage in shipping. We have sort of a “ribbed” beige case with a nice prominent IBM logo. To the left we have a large round power button as well as your led lights for power, HDD and Ethernet. Not to much room for external bays as we have a spot for a 1.44mb floppy mid case and to the right of it two 5 1/4 bays that I currently have a DVD drive installed in one and nothing in the lower bay. Stock this machine would have a CD drive installed rather then a DVD drive.

One feature of the type 6562 that is lacking on most other models of the 300PL line is the convenient front audio options.

ibm300pl2

We have a microphone jack and a headphone jack as well as a very convenient volume knob. My research indicates this was removed from later models due to the fact it was difficult to line up the case with the volume knob when putting the case top back in place though personally I have not found this to difficult. The built in audio is powered by a Crystal 4236B chip. It is possible to enhance the audio quality of the sound by replacing some caps but I will leave a link outlining this processed at the end of the article.

Looking at the back.

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You may notice in the image above that the case uses plastic tabs to shut which unfortunately were damaged in shipping so the case doesn’t quite snap back together properly. There are four expansion slots arranged in a vertical manner as well as a key slot for locking the machine if you were the type to do such things. Its inclusion does make sense seeing as these were likely heavily marketed to business. Starting at the lower left we have the usual suspects, audio in and out jacks along with built in Ethernet port, parallel port, two USB ports, two serial ports, ps/2 ports for keyboard and mouse and finally a built in VGA port. Having built in Ethernet and audio out of the box is a nice feature for a Pentium 1 machine.

The IBM 300PL uses a screwless case design which causes it to suffer similarly to others 90’s screwless cases. The plastic has become brittle with age and is easy to accidentally snap off making shipping and even routine case open and closings a risky endeavor.

ibm300pl4

Above are the internals along with a view of where the drives are oriented. One interesting thing about this motherboard that you can’t see to well in this image is that floppy, IDE and power connectors are all located on the riser card rather then the motherboard itself.

ibm300pl6

With the removal of two screws the 5 1/4 bays can fold up on a hing allowing easy access and revealing a bay on the underside for a hard drive. I like this feature as it makes swapping drives very easy.

The primary IDE connector is actually located on the side of the riser card facing 5 1/4 bays. The primary power connector is also located on this side which can be made out in the background.

ibm300pl7Now to take a look at the riser card itself.

ibm300pl8

Here you can see the secondary IDE connector as well as the floppy connector and power connector for the floppy drive, which is somewhat odd seeing as power is not being supplied by a cable straight off the power supply. This riser card has three PCI and two 16-bit ISA slots though one of the PCI/ISA slots is shared. This is more then adequate for a late DOS or early windows rig in my opinion

ibm300pl9

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1) CPU – The 300PL is an early socket 7 motherboard with the Triton II chipset which seems to have been a high-end offering at the time. My 300PL came with a Intel Pentium 200mhz installed but I upgraded it to a 233mhz MMX CPU which is officially the fastest CPU it can take. Upgrading the CPU is possible though with something like a PowerLeap PL-K6-III. The stock CPU does not come with a fan on the heatsink but the case fan is located directly below the CPU blowing air over the heatsink.

The 300PL has 512kb of on-board L2 cache which I suspect are the two chips located just above the CPU

2) The 300PL is very picky about RAM. According to official documentation it must be EDO nonparity (NP) or EDO error correcting code (ECC) DRAMs of up to 128mb in size. Mine currently has 128MB that came installed when I acquired this machine. The max RAM that is physically possible to install is 384mb since there are only three sockets for RAM and the machine is only capable of using 128MB sticks each. The chipset itself though is capable of supporting 512mb of RAM. I attempted to use various RAM sticks over 128mb and none were accepted.

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3) Video – The built in video chip is actually rather good and is the Matrox Mystique 1064SG-H chip. Not a surprising choice seeing as this machine has business uses in mind but it still makes a fast chip for DOS games and offers excellent 2d image quality as well as providing some early 3D abilities. The Mystique does have some compatibility issues with things like fog layers in some games but overall is a good chip, especially when paired with something like a Voodoo 1 or 2. The chip comes with 2mb of video SGRAM built into the board with the option to increase the amount to 4mb with an add on card. There is also connections for video option cards like the Rainbow Runner.

ibm300pl11

That white connector to the right is for an optional IR upgrade.

4) Switch block – Rather then use all jumpers to make settings IBM opted to use a nice switch block to help set things such as CPU speed. Here is a shot of the info sheet on what the switches control located on the underside of my case.

ibm300pl10

ibm300pl13(double click to enlarge)

5) CMOS Battery – Next to the switch block is also located the CMOS battery for saving changes made in the BIOS.

That’s about it for the IBM 300PL type 6562. It’s actually not a bad choice for a DOS machine or early Windows. The amount of options built in is nice and the the built in video is actually very good for the time especially when paired with a Voodoo card. The case, although very estheticly pleasing, at least to me, suffers from aging brittle plastic issues as do most screwless 90’s computers.

A great resource on the 300PL 6562 HERE

Benchmarks (Intel 233mhz MMX, 512kn L2 cache, 128 EDO RAM, Built-in Matrox Mystique 1064SG-H)

3D Bench – 163.6

PCP Bench – 58.1

DOOM – 82.7

Quake – 45.6

Speedsys – 175.43

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