Speed
Serial
- low-speed, cheap connections
- RS-232 1K–100Kbits/sec, copper wire
- medium-speed efficient connections
- I2C 10K-400Kbits/sec, board traces - IrDA 9.6K-4Mbits/sec, line-of-sight, .5m
- high-speed, expensive connections
- Ethernet 1.5-100Mbits/sec, twisted-pair or co-axial
- Firewire 1+Gbit/sec
Parallel
- low-speed, not too wide
- SCSI bus, 10Mbytes/sec, 8 bits wide
- NuBus, 40Mbytes/sec, 32 bits wide
- PCI bus, 250Mbytes/sec, 32 bits wide
- high-speed, very wide – memory systems in large multi-processors
- 200M-2Gbytes/sec, 128-256 bits wide