Abstract: A PCI/ISA bus single board computer card using EISA bus connectors and an EISA bus backplane slot for transmitting PCI bus and ISA bus signals. The computer card comprises EISA bus connectors having a first group of connectors interleaved with a second group of connectors. The first group of connectors transmit ISA bus signals and has a structure identical to conventional ISA bus connectors. The second group of connectors transmit PCI bus signals. The backplane comprises a plurality of PCI bus slots, a plurality of ISA bus slots and at least one EISA bus slot. Each slot comprises a plurality of clamping connectors. Each of the clamping connectors of the EISA bus slot has an upper part and a lower part. The upper part connects to a slot of the ISA bus and lower part connects to a slot of the PCI bus through the backplane circuit.