UTMC UT69R000-12WCC 12MHz 16-bit RISC -1992

We have previously covered several MIL-STD-1750A compatible processors as well as the history and design of them.  As a reminder the 1750A standard is an Instruction Set Architecture, specifying exactly what instructions the processor must support, and how it should process interrupts etc.  It is agnostic, meaning it doesn’t care. how that ISA is implemented, a designers can implement the design in CMOS, NMOS, Bipolar, or anything else needed to meet the physical needs, as long as it can process 1750A instructions.

Today we are going to look at the result of that by looking at a processor that ISN’T a 1750A design.  That processor is a 16-bit RISC processor originally made by UTMC (United Technologies Microelectronics Center).  UTMC was based in Colorado Springs, CO, and originally was formed to bring a semiconductor arm to United Technology, including their acquisition of Mostek, which later was sold to Thomson of France. After selling Mostek, UTMC focussed on the military/high reliability marked, making many ASICs and radhard parts including MIL-STD-1553 bus products and 1750A processors.  The UT69R000 was designed in the late 1980’s for use in military and space applications and is a fairly classic RISC design with 20 16-bit registers, a 32-bit Accumulator, a 64K data space and a 1M address space.  Internally it is built around a 32-bit ALU and can process instructions in 2 clock cycles, resulting in 8MIPS at 16MHz.  The 69R000 is built on a 1.5u twin-well CMOS process that is designed to be radiation hardened (this isn’t your normal PC processor afterall).  In 1998 UTMC sold its microelectronics division to Aeroflex, and today, it is part of the English company Cobham.

UTMC UT1750AR – 1990 RISC based 1750A Emulation

UTMC also made a 1750A processor, known as the UT1750AR, and if you might wonder why the ‘R’ is added at the end.  The ‘R’ denotes that this 1750A has a RISC mode available.  If the M1750 pin is tied high, the processor works as a 1750A processor, tied low, it runs in 16-bit RISC mode.  How is this possible? Because the UT1750AR is a UT69R000 processor internally.  Its the same die inside the package, and the pinout is almost the same (internally it may be but that’s hard to tell).  In order for the UT1750AR to work as a 1750A it needs an 8Kx16 external ROM.  This ROM (supplied by UTMC) includes translations from 1750A instructions to RISC macro-ops, not unlike how modern day processors handle x86.  The processor receives a 1750A instruction, passes it to the ROM for translation, and then processes the result in its native RISC instructions.   There is of course a performance penalty, processing code this way results in 1750A code execution rates of 0.8MIPS at 16MHz, a 90% performance hit over the native RISC.  For comparison sake, the Fairchild F9450 processor, also a 1750A compatible CPU, executes around 1.5MIPS at 20MHz (clock for clock, about 30% faster), and thats in a power hungry Bipolar process, so the RISC translation isn’t terrible for most uses.

NASA Aeronomy of Ice in the Mesosphere – Camera powered by RISC

By today’s standards, even of space based processors, the UT69R000 is a bit underpowered, but it still has found wide use in space applications.  Not as a main processor, but as a support processor, usually supporting equipment that needs to be always on, and always ready.  One of the more famous mission the UT69R000 served on was powering the twin uplink computers for the DAWN asteroid mission (which only this year ended).  It was also used on various instrumentation on the now retired Space Shuttles. The CPU also powered the camera system on the (also retired) Earth Observing-1 Satellite, taking stellar pictures of our planet for 16 years from 2000-2017.  Another user is the NASA AIM satellite that explores clouds at the edge of space, originally designed to last a couple years, its mission which started in 2007 is still going.  The

JAXA/ESA Hinode SOLAR-B Observatory

cameras providing the pretty pictures are powered by the UT69R000.  A JAXA/ESA mission known as SOLAR-B/Hinode is also still flying and running a Sun observing telescope powered by the little RISC processor.

There are many many more missions and uses of the UT69R000, finding them all is a bit tricky, as rarely does a processor like this get any of the press, its almost always the Command/Data Processor, these days things like the BAE RAD750, and LEON SPARC processors, but for many things in space, and on Earth, 16-bits its all the RISC you need.

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.

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.

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.

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.