January 20th, 2014 ~ by admin

Welcome Back Rosetta: The Dynex MAS31750 Awakens

Rosetta Comet Chaser - Dynex 1750

Rosetta Comet Chaser – Dynex 1750

The ESA’s comet chaser Rosetta has just today awoken from a long deep sleep on its comet chasing (and landing) mission.  The solar powered spacecraft was launched back in 2004.  It is based on the Mars Mariner II (itself based on the Voyager and Galileo) spacecraft design of the early 1990s (when the mission was first conceived.)  Main differences include using very large solar arrays versus a RT (Radioisotope Thermal Generator) and upgraded electronics.

In order to conserve power on its outward loop (near Jupiter’s orbit) most all systems were put to sleep in June of 2011 and a task set on the main computer to waken the spacecraft 2.5 years later and call home.  The computer in charge of that is powered by a Dynex MAS31750 16-bit processor running at 25MHz, based on the MIL-STD-1750A architecture.

A reader recently asked why such an old CPU design is still being used rather then say an x86 processor.  As mentioned above the Rosetta design was began in the 1990’s, the 1750A was THE standard high reliability processor at the time, so it wasn’t as out of date as it is now that its been flying through space for 10 years (and 10 years in the clean room).  The 1750A is also an open architecture, no licenses are or were required to develop a processor to support it (unlike x86). Modern designs do use more modern processors such as PowerPC based CPUs like the RAD750 and its older cousin the RAD6000.  Space system electronics will always lag current tech due to the very long lead times in their design (it may be 10 years of design n the ground before it flies, and the main computer is selected early on).  x86 is used in systems with 1) lots of power, and 2) somewhat easily accessible.  Notably the International Space Station and Hubble.  x86 was not designed with high reliability and radiation tolerance in mind, meaning other methods (hardware/software) have to be used to ensure it works in space.

Currently the ESA designs with an open-source processor known as the LEON, which is SPARC-V8 based.

November 19th, 2013 ~ by admin

MAVEN To Mars: Another BAE RAD750 CPU

MAVEN to Mars - RAD750 Powered

MAVEN to Mars – RAD750 Powered

NASA has successfully launched the $671 million MAVEN mission to Mars for atmospheric research.  Like the Mars Reconnaissance Orbiter it is based on, it’s main computer is a BAE RAD750,  a radiation hardened PowerPC 750 architecture.  This processor first flew on the Deep Impact Comet chaser and is capable of withstanding up to 1 million rads of radiation.  The entire processor sub-system can handle 200,000 rads.  To put this in perspective, 1000 rads is considered a lethal dose for a typical human.  Likely much higher then a Apple Mac G3 that the PowerPC 750 was originally used in back in 1998 as well.   The processor can be clocked at up to 200MHz though often will run slower for power conservation.

The MAVEN should reach Mars within a few days of the Indian Space Agency’s $71 million Mangalyaan Orbiter launched earlier this month.  MAVEN is taking a faster route, at the expense of a heavier booster and larger fuel consumption.  The Mangalyaan Orbiter’s main processor is the GEC/Plessey (Originally produced by Marconi and now Dynex) MAR31750, a MIL-STD-1750A processor system.

October 25th, 2013 ~ by admin

Honeywell 1750A-5V: MIL-STD-1750A Lives On

Honeywell 1750A-5V -2008

Honeywell 1750A-5V -2008

While its not in the best condition I was still pleased when it came in.  MIL-STD-1750A was first developed in 1980 to provide a uniform architecture for military computing, while allowing competition in the market to produce different versions at a hoped for reduced cost.  By 1996 though the 1750A was declared inactive for new designs in the US military.  It had been widely replaced by other more powerful commercial designs, notably the 80386 and 80486.  Many militaries around the world continue to use the 1750A and the US Military continues to need spares.

Honeywell continues to produce the 1750A-5V, a single chip implementation of the 1750A with on-board 40-bit FPU, much like Fairchild’s commercial F9450.  Produced on a CMOS SOI (SIlicon On Insulator) 0.65u process the 1750A-5V runs at up to 40MHz, twice as fast as most did in the 1980’s.  This particular example was produced in 2008 though Honeywell continues to make and advertise the 1750A.

The radiation hardened version was used on the Cassini Orbiter (now orbiting Saturn), ESA’s Rosetta Comet probe as well as the Guidance computer for the Air Force’s Titan 4 missile.

October 5th, 2012 ~ by admin

CPU of the Day: Fairchild F9450 – Commercial Military

Fairchild F9450 – 1985 – 10MHz

In 1980 the United States Air Force published a standard for a 16-bit Instruction Set Architecture (ISA) to meet their needs for computers on fighters etc.  This standard is known as MIL-STD-1750A and laid out what the processor needed to be able to do, but not how, or what would be used to accomplish it.  This allowed manufacturers to implement the standard in anyway they wanted.  It could be done in CMOS, Bipolar, SoS, GaAs or even ECL.  It was designed (like the Signetics 8X300 and the Ferranti F100) with real time processing in mind, similar to what we would call a DSP today.

Many companies made 1750A compatible processors including Honeywell, Performance Semiconductor (now Pyramid), Bendix (Allied), Fairchild, McDonnell Douglas, and others.  The processors ended up finding uses in many things outside of the USAF, including many satellites and spacecraft including the Mars Global Surveyor.  The standard was not restricted to military use, in fact commercializing it was encouraged, as this would increase production, which would help decrease costs for the military.

Fairchild designed the F9450 to meet both the commercial, and military markets.  Initial availability was in 1985 and the F9450 provides an on-board floating point unit, an optional, second chip, on other implementations.  Fairchild also made a F9451 MMU (Memory Management Unit), and a F9452 BPU (Block Protection Unit).  The 9450 was manufactured in a bipolar process (Fairchild called it I3L for Isoplanar Integrated Injection Logic).  This helped boost speed, as well as greatly increased reliability, as bipolar is much less susceptible to higher radiation levels then CMOS is.  Bipolar processes also generate heat, lots of it and to help counter this Fairchild used a somewhat unusual (for a processor) ceramic package made of Beryllium Oxide (BeO).  BeO has a higher thermal conductivity than any other non-metal except diamond, and actually exceeds that of some metals. Normally the ceramic on a CPU package is some form of Alumina (Al2O3).  Beryllium itself is a carcinogen so grinding, or acid application on BeO is not recommended.  The bottom of the the 9450 was made with a different ceramic, as the goal was to get the heat away from the chip, and not back into the PCB.  9450s were available in speeds of 10, 15 and 20MHz and in Commercial, or Military temperature rating.  MIL-STD-883 screening was of course available.

By 1996 the 1750A architecture was declared inactive and not recommended for new designs.  However, due to its extensive software support, reliability, and familiarity, it enjoys continued use, and is still being manufactured by several companies.