By John McHale
SAN DIEGO - Engineers at Space Electronics in San Diego have developed a commercial-off-the-shelf (COTS) computer for satellites and other space applications to compete with the RAD6000 from Lockheed Martin Federal systems in Manassas, Va.
The 6U VME SB486R radiation-hardened 32-bit single-board computer, based on Intel`s 80486 microprocessor, runs at a clock speed of 66 MHz and processes information at 54 million instructions per second.
It is the first board for space designed with primarily COTS components such as the Intel processor and the RAD-PAK part-level shielding technology from Space Electronics, says Stuart Shanken, sales and marketing manager at Space Electronics.
The SB486R is about half the price of a RAD6000 and should be shipping by the end of the year, claims David Czajkowski, the company`s space products business unit manager. Current applications include a NASA satellite and a military satellite. Space Electronics officials would not cite the specific projects.
Microprocessor features include on-or-off-chip data cache, floating point processing, paged or virtual memory management, and a RISC integer core.
The board contains 256k-by-40 of L2 cache SRAM, 64 megabytes to 2 gigabytes DRAM data storage, and 512 kilobytes to 2 megabytes EEPROM. The SB486R operates with the Wind River Systems VxWorks 5.3.1 real-time operating system.
Radiation performance
The SB486R can withstand a total ionizing dose of radiation to 100 kilorads for low Earth orbit. The level is based on a combination of inherent die level radiation performance for each integrated circuit and Space Electronics RAD-PAK.
The board resists single event latchup through a combination of careful selection of integrated circuit functions, custom manufacturing of key integrated circuits, and Space Electronics Latchup Protection Technology, giving the board an estimated probability of single-event latchup of once every 500,000,000 years in low-Earth-orbit, Space Electronics officials say.
The SB486R combats single event upsets with memory error correction and detection, as well as memory scrubbing for its primary and external cache memories. Space Electronics experts say their board is prone to single-event upset only once every 27 years.
Memory scrubbing involves a routine that periodically removes the single-event latchups that occur when memories are not active.
The Space Electronics-treated 80486DX2-microprocessor uses a single-event upset monitoring circuit that provides an input signal to the integrated circuit. If the microprocessor provides an incorrect response, the firmware authorizes a self-correction subroutine that puts the microprocessor back on track.
An optional architecture that combines the SB486R single-event upset enhancement techniques with a redundant 80486DX2-processor and comparison hardware is available in the SB486SR. This enhancement is also known as duplex or lockstep hardware that improves the single-event upset level to one upset every 100,000 days.
Duplex hardware involves the use of two central processors, with the comparison device checking both processors for an error. When data from the two processors does not match a single-event upset has occurred.
The hardware automatically detects any single-event upset within the microprocessor and the software corrects it.
For more information on the SB486R or Space Electronics contact David Czajkowski by phone at 619-452-4167, by fax at 619-452-5499, or on the World Wide Web at http://www.spaceelectronics.com.
The SB486 single-board computer from Space Electronics in San Diego. is targeted for space applications
