Perseverance's CPU

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Winston

Lorenzo von Matterhorn
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The much larger feature size than in current CPUs makes it much more glitch proof from radiation. They also use a "radiation-hardened bulk CMOS" process.

NASA’s latest Mars rover has the same processor as an iMac from 1998
2 Mar 2021


NASA’s brand-new Perseverance rover is the most advanced machine that’s ever landed on Mars. But when it comes to rovers, “state of the art” is a subjective term. Perseverance is running on none other than a PowerPC 750, a single-core, 233MHz processor with just 6 million transistors that’s most famous for powering the original “Bondi blue” iMac from 1998. It’s the same type of processor that NASA already uses in its Curiosity rover.

That’s largely because Mars’ atmosphere offers far less protection from harmful radiation and charged particles than Earth’s atmosphere. A bad burst of radiation can badly wreck the sensitive electronics of a modern processor — and the more complex the chip, the more can go wrong. Plus, at 138 million miles away, it’s not like NASA can just swap out the processor if things go sideways. Because of those conditions, Perseverance actually features two computing modules: one is a backup just in case something goes wrong. (A third copy of the module is also on board for image analysis.)

To make the system even more durable, the PowerPC 750 chip in Perseverance is a little different than the one in the old iMacs. It’s technically a RAD750 chip, a special variant that’s hardened against radiation and costs upwards of $200,000. The chip is popular for spacecraft, too: in addition to Perseverance and Curiosity, it also powers the Fermi Space Telescope, the Lunar Reconnaissance Orbiter, the Deep Impact comet-hunting spacecraft, and the Kepler telescope, among others.

While the processor may be weak compared to a modern smartphone or gaming PC, NASA’s spec sheet for Perseverance notes that it’s far more powerful than earlier rovers like Spirit or Opportunity: its 200MHz clock speed is 10 times faster than those older rovers, and with 2GB of flash memory, it offers eight times the storage. (Rounding things out, Perseverance also has 256MB of RAM in case you were looking to build your own rover.)

RAD750


The CPU has 10.4 million transistors, an order of magnitude more than the RAD6000 (which had 1.1 million). It is manufactured using either 250 or 150 nm photolithography and has a die area of 130 mm2. It has a core clock of 110 to 200 MHz and can process at 266 MIPS or more. The CPU can include an extended L2 cache to improve performance. The CPU itself can withstand 200,000 to 1,000,000 rads (2,000 to 10,000 gray), temperature ranges between –55 °C and 125 °C and requires 5 watts of power. The standard RAD750 single-board system (CPU and motherboard) can withstand 100,000 rads (1,000 gray), temperature ranges between –55 °C and 70 °C and requires 10 watts of power.

The RAD750 system has a price that is comparable to the RAD6000, the latter of which as of 2002 was listed at US$200,000 (equivalent to $284,292 in 2019).

In 2010, it was reported that there were over 150 RAD750s used in a variety of spacecraft.[6] Notable examples, in order of launch date, include:

Deep Impact comet chasing spacecraft, launched in January 2005 - first to use the RAD750 computer.
XSS 11, small experimental satellite, launched 11 April 2005
Mars Reconnaissance Orbiter, launched 12 August 2005
SECCHI (Sun Earth Connection Coronal and Heliospheric Investigation) instrument package[7] on each of the STEREO spacecraft, launched 15 October 2006
WorldView-1 satellite, launched 18 September 2007 - has two RAD750s.
Fermi Gamma-ray Space Telescope, formerly GLAST, launched 11 June 2008
Kepler space telescope, launched in March 2009
Lunar Reconnaissance Orbiter, launched on 18 June 2009
Wide-field Infrared Survey Explorer (WISE), launched 14 December 2009
Solar Dynamics Observatory, launched 11 February 2010
Juno spacecraft, launched 5 August 2011
Curiosity rover, launched 26 November 2011
Van Allen Probes, launched on 30 August 2012
InSight, launched on 5 May 2018
Perseverance rover, launched 30 July 2020.
 
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