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IBM Personal Computer (5150)

5150 · 1981–1987 · desktop

Specifications

Cpu: Intel 8088, 4.77 MHz
Ram: max: 256 KB on the motherboard with all banks populated, up to 640 KB with expansion cards · base: 16 KB on the motherboard (some early units 64 KB)
Ports: Cassette port (DIN) · Keyboard port (5-pin DIN) · 5 internal ISA expansion slots · Parallel (Centronics) via add-in card · Serial (RS-232) via add-in card · Composite video via CGA card
Display: IBM Color Graphics Adapter (CGA, optional) up to 320x200 in 4 colors or 640x200 monochrome, or IBM Monochrome Display Adapter (MDA) 80x25 text only; both sold as separate cards
Storage: base: Cassette port (no internal storage on the base configuration) · options: One or two 5.25" single-sided 160 KB floppy drives · Third-party hard card and hard drive add-in boards, not officially supported until the XT
Os Support: latest: PC DOS 3.3 ran on the 5150, though most later DOS and third-party OS releases assumed more RAM and a hard disk than the base 5150 offered · shipped: PC DOS 1.0 or IBM Cassette BASIC in ROM
Release Price: $1,565 (base cassette configuration, no monitor)

Variants

Models

Cassette configurationCheapest configuration: 16 KB RAM, no floppy drives, boots to Cassette BASIC in ROM and stores programs on standard audio cassette.

Dual floppy configurationAdds one or two 5.25" 160 KB floppy drives and enough RAM to run PC DOS, the far more common real-world setup.

Upgrade paths

RAM

640 KB total (256 KB on-board plus expansion cards into the 5 ISA slots) · The motherboard itself topped out at 256 KB across its DIP banks; reaching the DOS 640 KB ceiling required a memory expansion card in one of the ISA slots.

~$400-$700 for a populated expansion card at the time

MODERATE

storage

Two internal 5.25" floppy drives, or a third-party hard card/hard drive controller in an ISA slot · IBM did not offer an official internal hard drive for the 5150 (that arrived with the PC XT in 1983); owners retrofitted add-in controller cards and drives instead.

~$500+ for a floppy drive kit, more for early third-party hard drives

MODERATE

display

CGA or MDA graphics card, or later a Hercules-compatible card for monochrome graphics · Video was entirely add-in: the base unit had no on-board display hardware, so the card chosen determined whether the machine could do color graphics at all.

~$200-$300 for a graphics card at the time

EASY

CPU

Intel 8087 math coprocessor added to the empty socket next to the 8088 · The 8087 only accelerated floating-point math for software written to use it; it did not speed up general computing.

~$150-$200 at the time

EASY