6.1.1.7.

B. Video local bus (VL-Bus)

Local bus works by allowing CPU communications with peripheral devices to bypass the expansion bus bottleneck, thereby enhancing performance by allowing the CPU itself to work at optimum speeds. The performance gains achieved by local bus technology can be considerable in processor-intensive communications with peripherals, but until recently there was no universally agreed local bus standard. Now, however, the Video Electronic Standards Association (VESA) has proposed one, which an increasing number of manufacturers are offering in their products. A few manufacturers (eg Dell) continue to offer their own proprietary local bus solutions.

The advantages of VL-Bus are that it works and doesn't cost very much to implement. The ultimate disadvantage is that it still depends on a 12 year old PC design that is essentially obsolete. In addition, VL-Bus cards are specified for 25 and 33 MHz systems (or doubled-up versions of them), so they are not stable in DX50 systems. Even though VESA has already defined a 64-bit version of VL-Bus to take advantage of the next generation of Intel processors (ie the Pentium) in competition with PCI (see below) - the VESA 2 VL-Bus standard, which will support DX50 processors - VL-Bus will have an uphill struggle against PCI, whose architecture is universally regarded as being superior to that of VESA VL-Bus. However, the claim that VL-Bus is processor dependent in the sense of being able to work only with 486 machines appears to be untrue since at least two manufacturers (Elonex and ALR) are offering Pentium machines with VL-Bus.