[Sis-csi] VxWorks vs. Linux

Jim Benson Jim at SpaceDev.com
Thu Jan 25 19:00:49 EST 2007

For whatever it is worth, and as the pioneer of the MPC750 and VxWorks in space, we have abandoned both and are now going with much more advanced commercial off-the-shelf processors and are running Linux (with Ethernet and USB connections for all plug and play subsystems) on our three formation-flying, networked  microsats for the Missile Defense Agency.

Onward and upward,

Jim Benson

-----Original Message-----
From: sis-csi-bounces at mailman.ccsds.org [mailto:sis-csi-bounces at mailman.ccsds.org] On Behalf Of Leigh Torgerson
Sent: Thursday, January 25, 2007 3:49 PM
To: Scott, Keith L.; Marc Blanchet; Lloyd Wood
Cc: sis-csi at mailman.ccsds.org
Subject: RE: [Sis-csi] 2:30 Eastern it is

Just as an aside, this discussion thread is fundamentally why we ported CFDP/TM/TC into a VirtexII Pro FPGA.

With the Deep Impact telemetry stack implemented in FSW (VxWorks) on a PPC750, lab tests showed a couple of megabits/sec max throughput with a full software implementation of the stack (with something like 67% CPU utilization if I remember

With our TRIGA FPGA implementation, we've run CFDP/TM/TC at 600 Mbps in reliable mode. This implementation is being looked at for porting to an Electra slice, using the rad hard version of the FPGA and a SPACR co-processor (used to manage CFDP state).

The flight software does a couple of register writes to the FPGA to set up the metadata and start a transaction, the FPGA interfaces with mass storage over an LVDS interface and conducts the transaction, including any retransmissions, and many of these flight software optimization / OS discussions become moot.

We've got AOS (partial implementation to support
DTN-BP) in the FPGA stack now, and the port of DTN-BP has commenced. Also being worked is the FPGA interface for AMS, and we've started the LTP FPGA design.


At 5:00 PM -0500 1/25/07, Scott, Keith L. wrote:
>I think this is correct.  One step is to ask the question: how fast do 
>we think we could forward packets in space?  The answer depends on the 
>hardware/software available, which will probably be (for the near
>future) VxWorks or some variant.  I suspect that the whole matter is 
>moot if we assume that the packet forwarding isn't sharing resources 
>with the C&DH, as even relatively weak machines can probably outstrip 
>current uplink rates (of TDRSS' 25Mbps, e.g.) by a factor of 2; 
>moderate or powerful machines (in a flight-qualifiable context) by 
>factors of 2-4.
>		--keith
>-----Original Message-----
>From: sis-csi-bounces at mailman.ccsds.org 
>[mailto:sis-csi-bounces at mailman.ccsds.org] On Behalf Of Marc Blanchet
>Sent: Thursday, January 25, 2007 4:56 PM
>To: Lloyd Wood
>Cc: sis-csi at mailman.ccsds.org
>Subject: Re: [Sis-csi] 2:30 Eastern it is
>Le 07-01-25 à 16:44, Lloyd Wood a écrit :
>>  At Thursday 25/01/2007 15:45 -0500, Marc Blanchet wrote:
>>>>  What rates can VxWorks forward at over the past N years?
>>>>  VxWorks -- how fast can the network stack forward.
>>>  why bind standards and architecture with specific stack/OS  
>>> implementation?
>>  because you want implementations, and what good is a standard  
>> without implementations?
>of course.
>>  The 'real world' choices for operating systems in space hardware  
>> tend to be VxWorks or RTEMS. What these two OS architectures have  
>> matters for implementation - e.g. RTEMS lacks processes/memory  
>> management.
>ok. but I can run a vxworks stack on a 3Ghz intel quad cpu or on a 
>100Mhz ARM.
>>  I think an appreciation of how much performance you can get out of  
>> real-world space hardware is important and has ramifications for  
>> architecture/design decisions.
>then, the question should be two-fold:
>a) hardware current and planned. max throughput
>b) penality of stack/OS (preferably on that hardware).
>taking b) only to me does not help.
>>  The effects of Moore's law are brutal in space (exponential  
>> increase seems slower than on Earth, so there's a gap) and thanks  to 
>> power/radhard requirements the processors used are slow. You'll  be 
>> imo lucky to achieve 10Mbps line rate from a stack running on a  
>> power-conserving general-purpose processor without hardware assist  
>> or brutal performance tweaking.
>>  L.
>IPv6 book: Migrating to IPv6, Wiley, 2006, http://www.ipv6book.ca
>Sis-CSI mailing list
>Sis-CSI at mailman.ccsds.org
>Sis-CSI mailing list
>Sis-CSI at mailman.ccsds.org

J. Leigh Torgerson                          ltorgerson at jpl.nasa.gov
Jet Propulsion Laboratory - Communications Systems Research Sec.332 DARPA DTN / DSMS Advanced Protocol Implementation Work Area Manager
(818) 393-0695                                   (818) 393-4643 fax

Sis-CSI mailing list
Sis-CSI at mailman.ccsds.org

More information about the Sis-CSI mailing list