By John Keller
GENEVA - Backers of an initiative to speed VMEbus throughput were to demonstrate VME running at 533 megabytes per second late last month at the SysComms `98 conference in Geneva, industry sources say.
This demonstration follows a string of recent and drastic improvements to VMEbus over the past 15 months that has increased its bandwidth from 320 to 533 megabytes per second. VMEbus at 64 bits typically runs at 80 megabytes per second, and industry has demonstrated throughput of 160 megabytes per second for the so-called "2E VME."
VMEbus with more than half a gigabyte of bandwidth could benefit a wide range of VME applications, experts say.
On the low end of applications, it would speed the flow of instructions and data I/O within 21-slot VME card cages. On the high end, it would speed intra-chassis communications, as well as set the stage for existing high-throughput data links.
"Very little is more important in the VME world than moving data faster between boards," says Rodger Hosking, vice president of Pentek Inc. of Upper Saddle River, N.J. Pentek engineers specialize in single-board digital signal processing (DSP).
"Processor speeds have increased, so the Texas Instruments C60 family of DSPs can move data at 800 megabytes per second in and out of their 32-bit data ports," Hosking says. "We have got higher-speed peripheral devices, faster A-D converters, wide-band communications channels such as Fibrechannel. We`ve got all these new processors and I/O interfaces populating VME boards, and if you can`t communicate between boards, the bus is a bottleneck."
Hosking cautions, however, that VME 533 will be of little benefit to single-board processor suppliers and systems integrators until interface hardware becomes widely available, and until industry settles on standards that govern the VME 533 interface.
"VME 533 would be a large step in performance that would be an obvious win if and when it becomes real," Hosking says. The challenge, he says, "is getting enough critical mass to get VME board vendors to adopt these standards. More and more of the acceptance is based on how well it works, how easy it is to support, and how freely available are the documentation and supporting chipsets."
It is not yet clear how soon industry might tool up to manufacture VME 533 on any significant scale.
Set to demonstrate VMEbus running at 533 megabytes per second are experts from Arizona Digital of Scottsdale, Ariz., Bustronic Corp. of Fremont, Calif., and the VME International Trade Association of Scottsdale, Ariz.
VME 533 would be backward compatible with existing VME technology by retaining the VME64 96-pin DIN connector, and would accept older 6U VME printed circuit cards, industry sources say.
Although this kind of bandwidth for VMEbus might make it competitive in terms of sheer throughput with other high-speed data buses such as Raceway, Myrinet, and Skychannel, industry experts say VME 533 would be more likely to complement these data links in future system designs.
"We are strong supporters of VME. This progression of bandwidth means VME stays alive and very much viable for systems that we need to build," says Richard Jaenicke, director of marketing at Sky Computers Inc. of Chelmsford, Mass.
Sky engineers supply Skychannel, a 320-megabyte-per-second data link between boards and between card chassis.
"You have a [VME] bus running at 533 running on P-1, shared between 21 slots," Jaenicke explains. "On Skychannel you have it on P2 where each board runs at 320 megabytes per second, but each gets its own dedicated connection through a crossbar. You get aggregate bandwidth of 2,560 megabytes per second. Skychannel is also a link between chassis. We use the same cables and connectors used for Fibrechannel when it runs over copper. We can connect multiple chassis together so you can have a single unified system."
