Stands for "VESA Local Bus."
VLB, also abbreviated as VL-bus, is an expansion bus on some computer motherboards. A VLB interface adds an expansion slot for a video card to accelerate graphics processing. A VLB expansion slot consists of an ISA slot paired with an additional slot in line behind it. It offered memory bandwidth of up to 200 MB/s when used with a 50 MHz 486 processor, compared to a maximum of 16 MB/s over the ISA bus.
The VLB interface was created in 1992 and was often included on motherboards designed for the Intel 486 processor. The ISA bus standard on computers of the time had insufficient bandwidth for graphics cards, which were becoming increasingly popular with the rise of graphical user interfaces. The Video Electronics Standards Association (VESA) designed the VLB standard to extend the ISA bus with an additional connector for higher memory bandwidth for more advanced graphics cards.
The VLB interface was available on computer motherboards for only a few years. Since the VLB interface was designed for the 486 processor generation, it was deprecated following the introduction of the Intel Pentium processor. Chipsets designed for the Pentium processor included the PCI bus, offering expansion slots with faster speeds than ISA slots at a much smaller size than VLB slots.