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Why Are VME Solutions
So Expensive?
By Jerry Gipper, Director of Marketing, Embedded Technologies, Motorola Computer Group, Tempe, AZ
It's often heard that VMEbus solutions are more expensive than PC solutions for technical embedded applications. Are VME solutions really more expensive? If VME solutions are more expensive, why are they more expensive? What costs associated with VME make it more expensive than PC solutions? Technical embedded applications are what VME is designed for and continues to be a major contributor. But why is it RcheaperS to use a PC than a VME solution?
Let's take a look at some of the items that should be considered when developing a technical embedded computer solution. The focus here is on the technical embedded type of real-time applications that need industrial strength solutions, the VME "sweet spot." Five major cost areas that deserve attention are: 1) Reliability, including system availability and serviceability, 2) Modularity, including expansion capability and processor scalability, 3) Market characteristics, 4) Hardware and software costs, 5) Technical support.
After looking at each of these items, we should have a better understanding of where key cost items are hidden.
Reliability
Many technical applications require high reliability, high availability, and must be easy to service. PC solutions do not directly address this need. VME is more capable of meeting reliability requirements. For example, the VME architecture allows for better air flow, a passive backplane with pin-in-socket DIN connectors, and combinations of front panel and rear panel I/O, all which add up to a more reliable, more available, and more serviceable system. If a PC system fails, the fastest way to get it back up and running is to replace the complete system. The smallest field replaceable unit is typically the entire system. Imagine trying to remove all the cables in a fully loaded PC to do a quick swap-out. VME systems, with the cabling out the back, can be brought back on-line with a minimum amount of cable moving and board swapping.
Modularity
Many mid to high end embedded systems require additional I/O, scaleable processing, or upgrade capability. Easy to configure expansion slots are key to meeting these requirements. VME supports up to 21 expansion slots without performance reducing "bus bridges." PCs typically only support 7 slots of expansion, of which only 3 to 4 slots are high performance PCI bus. PCI expansion is not ideally suited to multiprocessor or I/O expansion due to limited interrupt handling capability. To get the same level of expansion using a PC style solution requires bus bridges that impact the system performance. PCs are best suited to applications that have a limited need for expansion.
VME also supports many different mezzanine bus architectures that allow modularity at the individual board level. This gives a technical OEM the maximum flexibility in configuring systems.
Markets
Most VME vendors are very small in business size and focus on very specific market niches. They place a high value on every customer because every sale is very important to them. Their products must be pushed into the market. A customer has a high degree of leverage with the vendor because of the importance of each piece of business. If a customer needs a modification to a product, the vendor is willing to work with the customer to arrive at an acceptable solution. Most PC vendors live in a pull market where the consumer is driving the demand for the products. A technical OEM is a very small part of that market segment and thus has very little leverage with the PC vendor. Unique requirements are rarely entertained unless accompanied by very large orders. This is often not possible because the technical OEM usually only needs something less than 500 units per year which is not enough to get the attention of most PC vendors. The size of typical embedded projects favor VME solutions in most cases.
In addition to the leverage a customer has in the VME market, there is a tremendous number of niche products that directly address real-time embedded applications. With over 300 VME suppliers worldwide, there is a bounty of board-level solutions.
A third market element that VME vendors understand much better than PC vendors is the life cycle of an embedded computer solution. It is not unusual for embedded computers to have a life cycle of 5 to 15 years, well beyond the life of any typical PC. VME vendors understand this life cycle and strive to provide products to the market that can reasonably meet these life cycle expectations.
Hardware/Software Cost
VME products today are starting to leverage the PC component market by using architectures such as PCI bus as part of the underlying backbone of the boards. This allows VME suppliers to use high volume, lower cost PC components and thus ride this wave of lower cost. Unfortunately the VME market is not large enough to fully utilize the volume purchasing of the PC market. VME probably loses something in the order of 10-15% due to lower purchasing power. As mentioned earlier, a typical VME project ships somewhere in the neighborhood of 250 to 500 units over the life of the project, a long way from the hundreds of thousands of PCs shipped in a typical product generation.
Software costs for VME and PC solutions are approximately equal. VME products leverage the PC software wherever possible. VME does have the advantage in that virtually all microprocessors are available in a VME form factor and so the related operating systems and real-time kernels are also available on the VME platforms. The total software edge, for embedded applications, would have to go to VME.
Technical Support
Vendors of VME products have developed, over the years, solutions that fit into many niche markets. These vendors also provide more than just hardware or software solutions, they provide "support" for these products as well. What do we mean by support?
VME vendors provide extensive consulting in the form of integration assistance, driver development, BIOS modification, system debugging, product customization, revision management, and much more. How many PC vendors can devote hundreds of hours of support to get your system integrated and running in your final application? Not many I would guess, at least not without charging you appropriately. What you find in the technical embedded world is a support network of vendors that offer these services to their customers. The cost of this service is embedded in the price of the products. The additional cost of VME and VME like solutions such as CompactPCI buys you this extra level of ongoing support- support that is key to getting a final product to market. In the PC world, you are on your own if the going gets tough. No one is going to be there to spend the weekend helping you debug your code or find the missing jumper!
Summary
VME solutions are going to be anywhere from 25 to 75% more expensive for the hardware than an equivalent PC solution. When the other "features" discussed here are compensated for, the gap becomes minimal. Exactly how much depends on what value is placed on these other "features." In comparision, CompactPCI and Passive PCI are most likely going to be similar in cost structure to VME. At best they are going to be 5 to 15%, respectively, more cost effective than VME due to their stronger leveraging of PCI bus.
On the surface, VME is going to appear to be a more expensive solution. But that solution provides the user with more than just an embedded technical computing platform, it also provides a support channel that will be there when help is needed- support that is ready to assist you in getting your product to market quickly and effectively. This extra cost can be considered "insurance" that you will have a successful product. The question that you must ask yourself is "What is the true value of these "features"?"Most of these costs do not become evident until well into the product development or later in the production of the product. Be sure that you understand all of the costs so that you can select the right VME solution.
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