CompactFlash

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CompactFlash (CF) is the pioneering solid-state removable memory card standard introduced by SanDisk in 1994 and maintained by the CompactFlash Association (CFA). Based on a 50-pin Parallel ATA (PATA / IDE) interface, it dominated professional DSLR photography and industrial computing for two decades, scaling through CF+ specifications up to UDMA 7 (167 MB/s).

Source: CompactFlash Association (CFA) CF Specification v1.0–v6.0 / ANSI ATA/ATAPI · Last reviewed Aug 28, 2026

Specs

Governing Body	CompactFlash Association (CFA)
Introduction Year	1994 (SanDisk)
Physical Dimensions	36.4 mm × 42.8 mm × 3.3 mm (Type I) / 5.0 mm (Type II)
Physical Connector Form Factor	50-pin female socket receptacle (2 rows of 25 pins on 1.27 mm pitch)
Interface Protocol	Parallel ATA (PATA) / True IDE Mode / PCMCIA Memory Mode
Max Bus Speed Tier	UDMA 7 (167 MB/s @ 133 MHz PATA clock in CF 6.0)
Operating Voltages	Dual voltage: 3.3V (low power) or 5.0V (legacy standard)
Video Performance Guarantee	VPG-20 (20 MB/s) / VPG-65 (65 MB/s sustained write for Full HD / 4K)

True IDE Protocol and Type I vs Type II

CompactFlash was unique among memory cards because it integrated a full IDE disk controller. In 'True IDE Mode', a host computer or embedded system treated the CF card as a standard PATA/IDE hard drive, making it a staple for boot drives in industrial PCs and network routers. Type I cards were 3.3 mm thick, while Type II cards (5.0 mm thick) were designed to house mechanical miniature rotating magnetic disks like the IBM Microdrive (170 MB to 8 GB).

Physical Pin Vulnerability and UDMA Scaling

Because CompactFlash used a 50-pin female receptacle mating with 50 rigid male header pins inside the camera or reader, slightly misaligned card insertion could easily bend or break reader pins, requiring expensive repairs. CF reached its physical and electrical limit with CF 6.0 (UDMA 7 at 167 MB/s), prompting the CFA to transition to serial interfaces (CFast and CFexpress).