First introduced in an 8-bit configuration in 1981 and upgraded to 16-bit in 1984, the venerable ISA bus has all but disappeared from mainstream computing. However, in the embedded space, this legacy architecture has, to date, maintained a viable position. How long can it continue to do so? And, should anyone even care?
Today, most new hardware utilizes far faster architectures. VME and PCI, in their most widely used forms, are both predominately 64-bit architectures. High-speed serial interconnects such as PCI Express and switch fabric architectures are clearly preferred for most computing applications, ranging from SOHO machines to supercomputers. Indeed, the ISA bus is far too slow for most of today's applications. Yet, it is still utilized in many legacy industrial automation applications where it is "good enough," and has also maintained a niche in those industrial and military applications that use expensive, highly specialized expansion cards that are not available in faster PCI, VME or switch fabric enabled configurations.
VDC has recently completed analyses of the markets for Slot Single Board Computers (used in passive backplane systems) and for Embedded Motherboards. The latter (motherboard) study shows that, in 2009, only 1% of Desktop Form Factor Class motherboards shipped actually included ISA expansion capability, and that even this is expected to disappear by 2012. ISA expansion is not even offered in most xITX and Embedded Class motherboards. ISA Slot Single Board Computer shipments comprised only 1% of SBC shipments in 2009 and are barely projected to maintain this share through 2012 - representing an actual 20% decline in shipments over the period.
One might therefore conclude this data trend sounds the death knell for ISA. However, the hybrid PCI-ISA configuration PICMG 1.0 not only represented 7% of total dollar volume SBC shipments in 2009, but is projected to continue to represent 6% of shipments in 2012. This implies a 3.6% real growth in shipments over the period. Edge-connected PCI SBCs (without the ISA capability) represented only 5% of total SBC shipments in 2009, a share which is expected to remain flat through 2012.
Why should the PICMG architecture, introduced in 1994, be able maintain such a position over the 2009-2012 time frame? Clearly, there can be only one reason - its provision of the ISA bus. Through the utilization of PICMG 1.0 architecture SBCs, users may take advantage of the increased compute capabilities of modern processors without being forced to abandon their investment in expensive specialized ISA expansion cards and their associated software.
VDC doubts that these specialized ISA boards will ever be ported to PCI. Rather, we suspect that if "new generations" of these ever appear, they will leapfrog right over PCI to PCI Express. In high volume markets such as desktop PCs, even the PCI bus is rapidly being supplanted by PCI Express. It's actually becoming somewhat difficult to buy a new SOHO computer that has even a single PCI slot. Of course, in order for this migration to PCI Express to occur, either PCI Express passive backplane systems would have to be made available, or users would have to forego the advantages of passive backplane systems and adopt active backplane systems for these applications.
It appears to us that the ISA bus still has "legs," and will be around for the next several years. As to the question of "should anyone care?" - that depends on who you are. If your applications rely on legacy ISA hardware, you clearly do care. In our opinion you may rest easy for at least a few more years.
VDC recently published industry-leading research on the 2009 - 2014 Global Markets for Slot Single Board Computers and Embedded Motherboards. A link to this research may be found here.
For more information about this research effort or about VDC's Embedded Hardware and Systems research practice please contact VDC's Cyril Bernard ([email protected]) or visit www.vdcresearch.com.
Yep, I read that the 6-series chipsets don't even have PCI built-in, requiring a bridge for that too.
Posted by: Yuhong Bao | 09/27/2010 at 03:09 PM