ibm pc early


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Introduced August 12, 1981
Discontinued April 2, 1987
Introduction Price  


      The IBM PC ( Personal Computer ) model #5150, was conceived by a team of IBM engineers sent to Boca Raton, Florida in early 1980. IBM had watched the microcomputer market grow from its infancy as a kit building hobby market to a potential billion-dollar industry. They decided that it was time for the world's largest computer company to enter the market. The IBM PC debuted on August 12, 1981 and took the microcomputer market by storm. It wasn't because the PC was a truly cutting edge product, because it wasn't. What really created all the hoopla was that it was built by Big Blue and that set the standard that every other computer manufacturer was measured by. The original PC set many standards that can still be found in today's computers, such as the ISA bus. You can take a standard 8 bit ISA card from a 19 year old IBM PC and put it into a modern 400 MHz Pentium II computer and it will work.

      This exhibit is of the early PC made between 1981 and 1983. You can tell this by looking at the edge of the motherboard (see above picture). The early machines came with only 16k or 64k RAM on the motherboard and were so marked. In April 1983 the motherboard was changed to allow the use of larger 64k RAM chips allowing up to 256k RAM to be installed. Both machines were capable of being expanded to 640k through the use of expansion cards.

     The original PC did not have a hard drive option available through IBM, the power supply was too small, (only 63 watts), to support a hard drive option. Third party manufacturers filled this void with a kit that replaced the power supply and installed an IDE controller card. The original power supplies can be identified by the all black paint and the red warning sticker on top. (see above picture) Replacement power supplies will be an unpainted silver or gold color.

     Another tell tale sign of the early PC is the use of the INTEL 8088. You will see in later PCs the use of an AMD licensed version of the 8088.

      The PC was sold in a number of configurations beginning with the basic model which had no floppy drives and only 16k of RAM, mass storage of programs was supposedly to be done with a cassette tape drive connected to a port on the rear of the computer. The PC came with Microsoft Cassette BASIC built in and will default to it if during boot up it does not detect an operating system on floppy. The exhibit also has an IBM CGA (color graphics adapter) and is connected to an IBM #5153 color monitor.


System Architecture  
Microprocessor Intel 8088 used in early models (AMD was used in later models)
Clock speed 4.77Mhz
Bus type ISA (Industry Standard Architecture)
Bus width 8-bit
Interrupt levels 8 (6 usable)
DMA channels 4 (3 usable)
Standard on system board 16k, 64k, or 256k(only after 1983)
Maximum on system board 64k or 256k
Maximum total memory 640k
Memory speed and type 200ns dynamic ram chips
System board memory socket type 16 pin DIP
Number of memory module sockets 27 (3 banks of 9 chips)
Memory used on system board 1 soldered bank of 9-16k X 1(early) or 64k X 1(later) bit chips.

27-16k X 1 for early PC's (Pre 1983) or

27-64k X 1 for PC's after 1983

Standard Features


Disk Storage

ROM size 40k ***** Internal disk and tape drive bays 2 full height
Optional math coprocessor 8087 ***** Standard floppy drives 1 X 360k
Standard graphics none   Optional floppy drives:  
Parallel printer ports none   * 5 1/4 inch 360k Optional
RS232C serial ports none   * 5 1/4 inch 1.2MB No
Mouse ports none   * 3 1/2 inch 720k Optional
UART chip used NS8250B   * 3 1/2 inch 1.44MB No
Maximum speed 9600bps   * 3 1/2 inch 2.88MB No
CMOS real time clock no   Hard disk controller included No
CMOS RAM none      

Expansion Slots


Keyboard Specs.

Total adapter slots 5-8 bit   Number of keys 83
Number of 8/16/32 bit slots 5/0/0   Keyboard cable length 6 feet

Physical Specs.


Environmental Specs.

Dimensions:     Power supply output 63.5 watts
* Height 5.5 inches   Operating voltage @ 60 Hz 104-127VAC
* Width 19.5 inches   Maximum current 2.5 amps
* Depth 16.0 inches      
* Weight 25 pounds