RE: [rtl] VxWorks to Rtlinux experiences?

["Wright, Robert B." <wrightr1@eglin.af.mil>]

what is the difference in difficulty between rtl and vxworks when writing
device drivers?

rob

> -----Original Message-----
> From: Marko Rauhamaa [mailto:marko@tekelec.com]
> Sent: Thursday, January 14, 1999 1:27 PM
> To: wrightr1@eglin.af.mil
> Cc: marko@linux1.ca.tekelec.com; jbrandt@sadira.gb.nrao.edu;
> rtl@rtlinux.cs.nmt.edu
> 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        Marko.Rauhamaa@tekelec.com   (818) 878-6314
> Sr Project Engineer   http://www.tekelec.com/      Tekelec Inc
> 
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