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

Storage

Cassette-based (no floppy drive)1981 base configuration, no disk drive

Single floppy drive160KB single-sided 5.25" floppy, 1981

Dual floppy drives320KB total, two 5.25" floppy drives, 1981

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