VESA Local Bus

Ask a question about 'VESA Local Bus' Start a new discussion about 'VESA Local Bus' Answer questions from other users Full Discussion Forum

• 80486 dependence. The VESA Local Bus relied heavily on the Intel 80486
  Intel 80486
  
  The Intel i486, otherwise known as the 80486, was the first tightly pipeline x86 design. Introduced in 1989, it was also the first x86 chip to use more than a million transistors, due to a large on-chip cache and an integrated floating point unit....
   CPU's memory bus design. When the Pentium
  Pentium
  
  Introduced on March 22, 1993, the original Pentium was the first superscalar x86 architecture microprocessor. Its fifth-generation x86 microarchitecture was a direct extension of the 80486 architecture with dual integer pipeline s, a faster FPU unit, wider data bus, and features for further reduced address calculation latency....
   processor started to gain mass acceptance, circa 1995, there were major differences in its bus design, and the VESA Local Bus was not easily adaptable. This also made moving the bus to non-x86
  X86 architecture
  
  The generic term x86 refers to the most commercially successful instruction set architecture in the history of personal computing. It derived from the model numbers, ending in "86", of the first few processor generations Backward compatibility with the original Intel 8086....
   architectures nearly impossible. Few Pentium motherboards with VLB slots were ever made.

• Limited number of slots available. Most PCs that used VESA Local Bus had only one or two slots available, as opposed to 5 or 6 ISA slots. This was because, as a direct branch of the 80486 memory bus, the VESA Local Bus did not have the electrical ability to drive more than 1 or 2 (or 3 at the most) cards at a time.

• Reliability problems. The same electrical problems that limited the VESA Local Bus to 2 or 3 slots also limited its reliability. Glitches between cards were common, especially on low-end motherboard
  Motherboard
  
  A motherboard is the central printed circuit board in some complex electronic systems, such as modern personal computers. The motherboard is sometimes alternatively known as the mainboard, system board, or, on Apple Inc....
  s, and when important devices such as hard disk
  Hard disk
  
  A hard disk drive , commonly referred to as a hard drive, hard disk, or fixed disk drive, is a non-volatile storage device which stores digitally encoded data on rapidly rotating hard disk platters with magnetic surfaces....
   controllers were attached to the bus, there was the all-too-common possibility of massive data corruption
  Data corruption
  
  Data corruption refers to errors in computer data that occur during transmission or retrieval, introducing unintended changes to the original data....
  .

• Installation woes. The length of the slot and number of pins made VLB cards notoriously difficult to install and remove. The sheer mechanical effort required was stressful to both the card and the motherboard, and breakages were not uncommon. This was compounded by the extended length of the card logic board; often there was not enough room in the PC case to angle the card into the slot, requiring it to be pushed with great force straight down into the slot. To avoid excessive flexing of the motherboard during this action, the chassis and motherboard had to be designed with good, relatively closely spaced supports for the motherboard, which was not always the case. Also, to avoid excessive localized stress the person inserting the board had to distribute the downward force evenly across its top edge, which was not always the case, and of which ideal that person was not always aware.

Technical data

See also

• Industry Standard Architecture
  Industry Standard Architecture
  
  Industry Standard Architecture was a computer bus standard for IBM compatible computers....
    (ISA)
• Extended Industry Standard Architecture
  Extended Industry Standard Architecture
  
  The Extended Industry Standard Architecture is a bus standard for IBM compatible computers. It was announced in late 1988 by IBM PC compatible vendors as a counter to IBM's use of its Proprietary software MicroChannel Architecture in its IBM Personal System/2 series....
   (EISA)
• Micro Channel architecture
  Micro Channel architecture
  
  Micro Channel Architecture was a proprietary hardware 16-bit or 32-bit parallel communications computer bus created by International Business Machines in the 1980s for use on their new IBM Personal System/2 computers....
   (MCA)
• NuBus
  NuBus
  
  NuBus is a 32-bit series and parallel circuits#Parallel circuits computer bus, originally developed at MIT as a part of the NuMachine workstation project....
  
• Peripheral Component Interconnect
  Peripheral Component Interconnect
  
  The PCI Local Bus , or Conventional PCI, is a computer bus for attaching computer hardware in a computer. These devices can take either the form of an integrated circuit fitted onto the motherboard itself, called a planar device in the PCI specification or an expansion card that fits into a socket....
   (PCI)
• Accelerated Graphics Port
  Accelerated Graphics Port
  
  The Accelerated Graphics Port is a high-speed point-to-point channel for attaching a :Category:Graphics cards to a computer's motherboard, primarily to assist in the acceleration of 3D computer graphics....
   (AGP)
• PCI Express
  PCI Express
  
  Peripheral Component Interconnect Express , officially abbreviated as PCIe, is a computer expansion card standard designed to replace the older PCI Local Bus, PCI-X, and Accelerated Graphics Port standards....
   (PCIe)
• List of device bandwidths
  List of device bandwidths
  
  This is a list of device bandwidths: the net bit rate of some computer devices employing methods of data transport is quantified in units of kilobits per second , megabits per second , or gigabits per second as appropriate....
   (A useful listing of device bandwidths that include VLB)