AST FourPort and clones (4 port)
Accent Async-4 (4 port)
Arnet Multiport-8 (8 port)
Bell Technologies HUB6 (6 port)
Boca BB-1004, 1008 (4, 8 port) - no DTR, DSR, and CD [Reddit: Data mining Discussion] .:: www.xiuwushidai.com ::.
Boca BB-2016 (16 port)
Boca IO/AT66 (6 port)
Boca IO 2by4 (4 serial / 2 parallel, uses 5 IRQ's)
Computone ValuePort (4, 6, 8 port) (AST FourPort compatible) .:: www.uniatlantico.edu.co ::.
DigiBoard PC/X, PC/Xem, PCI/Xem, EISA/Xem, PCI/Xr (4, 8, 16 port) .:: rant.li ::.
Comtrol Hostess 550 (4, 8 port)
PC-COMM 4-port (4 port)
SIIG I/O Expander 4S (4 port, uses 4 IRQ's)
STB 4-COM (4 port)
Twincom ACI/550
Usenet Serial Board II (4 port)
Non-intelligent cards usually come in two varieties, one using standard com port addresses and use 4 IRQ's, and another that's AST FourPort compatible and uses a selectable block of addresses and a single IRQ. (Addresses and IRQ's are set using setserial.) If you're getting one of these cards, be sure to check which standard it conforms to, prices are no indication. [Cloud computing Community]
Computone IntelliPort II (4/8/16 port)
Cyclades Cyclom-Y (RISC-based, 8-32 ports) (ISA/PCI)
(driver)
Cyclades-Z (high-end, 16-64 ports) (PCI)
(driver)
DigiBoard PC/Xe (ISA), PC/Xi (EISA) and PC/Xeve
Equinox SST Intelligent serial I/O cards
(driver)
Hayes ESP 1, 2 and 8 port versions Included in kernel since 2.1.15. The driver for kernel versions 2.0.x can be found at .:: community.alexgyver.ru ::. (driver)
Stallion EasyIO (ISA) / EasyConnection 8/32 (ISA/MCA) / EasyConnection 8/64 (PCI) For DIP switch settings and configuration files check (driver)
Stallion EasyConnection 8/64 (ISA/EISA) / ONboard (ISA/EISA/MCA) / Brumby (ISA) The latest driver can be found at (driver)
Comtrol RocketPort (8/16/32 port)
(driver) (kernels 1.2.x). A driver for kernels 2.x can be found at .:: www.just.edu.jo ::. (driver)
DigiBoard COM/Xi Contact Simon Park (si@wimpol.demon.co.uk) or Mark Hatle (fray@krypton.mankato.msus.edu). NOTE: both email addresses seem not to exist any longer.
Moxa C102, C104, C168, C218 (8 port), C320 (8/16/24/32 expandable) and C320T
RISCom/8
Specialix SIO/XIO (modular, 4 to 32 ports)
Specialix IO8+ Contact