VESA local bus was an expansion bus used to overcome speed limitations imposed by ISA bus. In theory VLB could reach 1280 Mbit/s (with 40 MHz CPU) which was way more than ISA's 66.7 Mbit/s. The speed was initially required by graphics cards and SuperIO (combined storage/parallel/serial) controllers, so that's what most searches for VLB cards return now.

However I think speed improvements are welcome everywhere - were there other cards, like network controllers, sound cards or some other specialized devices (like data acquisition cards) that were designed for VLB? The fact that many 486 motherboards have 3 VLB slots suggest that there should be at least one more type of device for this bus. Or was this bus superseded by PCI before it was adopted by majority of manufacturers?

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    Most cards don't benefit from increased speed. If you're playing sound at 44,100 bits per second or sending half-duplex data at 10 Mbit per second, ISA works just fine. – Mark Feb 25 '17 at 21:07
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    Yeah, ISA has enough bandwidth for sound cards, but there are fields (scientific / industrial) where people want to have as high data rates as possible. Hence the question - were there any other devices that used VLB's higher data rate for their purposes or did everyone just move straight to PCI? – Algimantas Feb 25 '17 at 22:15

VLB was a stopgap solution to fix ISA. The 16-bit ISA bus originated in the original PC AT (1984) and was showing its age by the time of the 486. Not only was it 16-bits, system designers had long since decoupled the slot clock from the CPU clock to maintain compatibility with cards that assumed 8MHz.

The issues with this bus were evident as far back as the mid-1980's. IBM's evolution of ISA was the Microchannel (MCA) bus. It was a better bus than ISA, but it also had it's problems. MCA boards were about half the size of ISA boards, required more complicated glue logic, and there were licensing fees to be paid to IBM if you wanted to build an MCA machine. Tandy did this with the 5000MC, but very few others did. (Other issues with the MCA bus included the fact that there were performance issues in the PS/2 Model 80's implementation of 32-bit, and IBM itself undermined the bus by continuing to use ISA in the Model 25, 30, and 30/286.)

The troubles with MCA and the limitations of ISA left a vacuum that an industry consortium attempted to address with EISA. EISA had backward compatibility with ISA (including card size) and many of the same features of MCA, but was expensive and mostly wound up in servers and other relatively high end machines.

The net effect of all of this was that, particularly in the low to mid range market, PC's wound up confined to the 16-bit/8MHz ISA bus well into the 486-cycle. For most peripherals, this didn't matter, but fitting a 1024x768x8bpp display through an ISA bus represented a major performance bottleneck. This became even worse at 16bpp or when trying to animate things. (This is why NeXTStep required a better bus than ISA, and on-card video accelerator chips didn't help.)

And this is the gap that VLB was intended to fill - how to get large bitmaps into a frame buffer. Very little else was in scope. As a result VLB was designed in much the same way as ISA was originally, with the same bus and clock rate as the host CPU. With a 33MHz FSB, the VLB would run at 33MHz. With a 50MHz FSB, it'd run at 50MHz. This also had an impact on the number of slots... by the time you got to a 50MHz bus, I believe only one VLB slot was allowed. This turned out not to matter, because 486DX50 machines were difficult to engineer and the market quickly shifted over to 486DX2/66 machines with higher core clocks and 33MHz buses.

The net result of this is that the market for VLB cards was heavily biased toward video cards. (Which aligns with the fact that the V in VLB stands for VESA.) That said, there were also disk controllers and a few other types of boards, but they were never remotely as significant as video. If you really care about high performance disk or network I/O, you'd buy a machine with an EISA bus. (And there were EISA machines that had VLB slots as well for the video... VLB had higher raw transfer rates than EISA, so it was still useful for video even on EISA machine.)

With the Pentium-era, Intel immediately pushed PCI into the market as the high-end alternative. Pentium-class machines would have PCI for disk, video, and anything else that required performance, and have an on board bridge to some ISA slots for compatibility with legacy devices. While I believe there were some PCI motherboards with VLB/ISA slots, the market really shifted over to PCI. (Until AGP was introduced to solve the same sorts of video bandwidth problems for PCI machines that VLB solved for ISA machines.)


I really enjoy this site in general and am happy to finally be able to answer. Seeing VLB mentioned was a trip down memory lane and, like you, most of what I remember were display adapters with a handful of SCSI HBA's and primitive/proprietary RAID cards thrown in. That said, though, I thought I remembered seeing one or two VLB NIC's that were intended for the servers of the day (read: mostly Novell).

Check out BOCA's BOCALANcard-VL (P/N BEN1VL) - general reference here, which supported a singe 10BaseT interface. Even given the standards of the time this didn't make a lot of sense, given that 10M was perfectly fine on the ISA cards of the time.

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    Welcome to Retrocomputing, and thanks for the answer. If you have any questions (a half-remembered feature or a question about the implementation of a thing, perhaps?) please ask them. – wizzwizz4 Feb 26 '17 at 14:29

While rnxrx's answer shows that there were, in fact, some other cards designed for VESA Local Bus, I think the main thing to keep in mind here is:

  • The 486 was introduced in 1989
  • VLB was standardized in 1992
  • VLB was completely tied to the 486's architecture, and fundamentally incompatible with the Pentium; the first variants of Pentium came in 1993, and using VLB with anything non-486 required special adaptation circuitry
  • Work on PCI began in 1990, and PCI 2.0 (which, according to Wikipedia, was the first version that actually specified some of the things you'd expect in a hardware standard, such as a specification for the connector) was introduced in 1993
  • PCI was independent of the CPU architecture, and in fact saw widespread use for a decade until superceded by PCI Express in 2004 (and motherboards with PCI slots were widely available for far longer)

Also, keep in mind that VLB was really just an extension to the ISA bus, so you still had all the issues that you did with ISA, but could shuffle data faster. PCI solved a lot of those problems, not least by introducing auto configuration (also known as "plug and play", though full plug and play support obviously required more than just peripheral connector bus standard support).

In between VLB of 1992, and PCI of 1993-1994 or so, there just wasn't a lot of time for manufacturers to use the new bus. Also, by the time PCI entered the market it came with the promise of not being tied to yesterday's architecture (the 486). Remember that at the time, an upgrade cycle of a few years gave significant improvements in pretty much all measurable areas (storage, RAM, processing speed, graphics capability, ...), so pretty soon you'd either have upgraded to a system with PCI support anyway, or would accept that new systems were running circles around yours basically regardless of whether your network card was ISA, VLB or something else.

  • This answer started out as a comment, but then I decided to give it a try and fleshed it out more than the comment space allows for. Does this answer count as Reading Wikipedia as a Service? (Server Fault has Reading Manuals as a Service, so why could not Retrocomputing do, too?) – a CVn Feb 26 '17 at 19:08
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    While PCIe may have been released in 2004 in the early days it was mostly used for graphics cards and onboard perhiperals. It took many years for it to replace PCI as the dominant standard for other expansion cards. Even today many motherboards still come with PCI slots. – Peter Green Mar 1 '17 at 5:41

For such a small market window time wise, there was a bunch of activity. Off the top of my head:

  • SCSI Controllers from Adaptec, AMI, Tekram, Buslogic, DTC, Advansys, Ultrastore, and others
  • Always SCSI + EIDE controller
  • Caching EIDE from Tekram & Atronics
  • EIDE RAID from Promise
  • Ethernet from D-link, Cnet, Lantech, and many others
  • FDDI from Compu-Shack & Infosystems (no, I've never seen one)
  • Dual serial from Kouwell (no, I don't know why)
  • Miro video capture/playback and editing cards
  • Miro wavetable sound card (I never saw one)
  • 3DLabs 3D Blaster, pre-PCI Direct3D add-in card
  • Somewhere around here I've got a VLB card with SVGA, EIDE, FDC, CD-ROM, SIO, PIO & Game port all on one card.

And that's leaving out a lot of manufacturers, not to mention all the generics.

There weren't a lot of sound cards that I recall (no need for the speed), and I never heard of a data collection card of any type. VLB didn't last long enough for a 100base-T card to show up. I'm somewhat surprised no one shipped a Token Ring card, considering two shops managed to ship FDDI cards, but there you go.

  • Welcome to Retrocomputing Stack Exchange. Please read the tour to familiarise yourself with the site. Thanks for the answer - you have named lots of uses for this port! – wizzwizz4 Sep 19 '17 at 19:17

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