Date sent: Thu, 14 Jan 1999 11:26:37 -0800
From: Marko Rauhamaa <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
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Subject: Re: [rtl] VxWorks to Rtlinux experiences?
> > i'm trying to decide between VxWorks and rtlinux for an RTOS project. i'd
> > like hear your comments concerning vxworks if you have experience with it
> > and why you're considering rtlinux.
>
> We are trying to decide between those two, too. We haven't used either
> in our products yet, but here are some of the points we have been
> considering:
>
> - We may decide to use a MIPS clone for hardware reasons. VxWorks runs
> on MIPS. Linux does support MIPS, but MIPS is probably the least used
> Linux platform. Moreover, RT Linux would have to be ported to MIPS
> and I have no idea yet how big a task that would be (we might be
> willing to pay a fee if somebody did it, though).
>
> - AFAIK, VxWorks source code is not for sale. RTOS debugging is hard
> enough with source code, so not having it may make debugging much
> slower even if the bug is in our code. In addition, we may need some
> special tweaks of our own that may not be possible without the source
> code. The source code risk is increased by the fact that VxWorks is a
> single-source product.
>
> - With RT Linux we can place soft-RT modules in the Linux sandbox. That
> means that we can add unexpected new features later without risking
> the functionality of the hard-real-time core. With VxWorks, as with
> most other RTOSes, new features may affect the whole system (although
> I hear VxWorks offers per-task memory management as an option).
>
> - The function and feature list of VxWorks is impressive. Personally I
> find a bit risky, though, to have a single company develop and
> maintain such an amount of code. Most of those functions are used by
> hundred of thousands of people on the Linux side, so I tend to rely
> more on the quality of Linux. For example, we may even want to run an
> HTTP server on the processor -- VxWorks has it, but I'd rather run
> Apache under Linux.
>
> - RT Linux allows soft-RT-interrupts (eg, communication with the host)
> to have a lower priority than critical RT tasks. I don't know if
> VxWorks allows this. I'm afraid it may be difficult to estimate the
> worst-case timing of VxWorks built-in device drivers.
>
> - VxWorks is expensive.
>
>
> Marko
>
> --
> Marko Rauhamaa [EMAIL PROTECTED] (818) 878-6314
> Sr Project Engineer http://www.tekelec.com/ Tekelec Inc
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> For more information on Real-Time Linux see:
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>
I'm using both now in a control system for an optical interferometry
project called the CHARA Array (www.chara.gsu.edu). The
VxWorks part is there because JPL/NASA did some sub contract
work for us and that is what they use, the rest of the system is
RTL (which I really like by the way).
Both are excellent systems. VxWorks is much more mature and
MUCH MUCH MORE EXPENSIVE. RTL does not have all the bells
and whistles, but you can get around that in a lot of situations. In
our system we needed very fast digital servos (5kHz) and VxWorks
was not really up to it. JPL ended up creating their own real-time
engine that ran on top of VxWorks. I find that a bit of an expensive
way to get network services for an RT system, but it does work.
Basically I think the following generalizations hold:
- If money is no object VxWorks is great for slowish servos (Hz,
not kHz) and has full user support and runs on almost any
hardware.
- If you are short of cash (like a University) and don't mind not
having online support (but this email thing seems to work well) RTL
is an excellent choice.
Hope this helps,
Theo ten Brummelaar
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For more information on Real-Time Linux see:
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