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Re: eCos support JVM?


On Sunday 11 July 2004 16:07, Amy Yap Hai Sin wrote:
> Sir,
>
> Thanks for your reply.
> 1.    Is it means if i need to implement Java in eCos, then most probably i
> need to port from Wonka VM?
"Most probably", yes. Among open source VMs, I don't know which other ones 
have been ported to eCos; Kaffe, maybe.

> 2.    Is there any source available now?
The open-source version of Wonka can be found at <http://wonka.acunia.com>. It 
doesn't run on ARM7, because the memory management functions use sbrk() 
(which requires an MMU).

Unfortunately the company that originally developed Wonka now does very little 
work on it, so the site is not well maintained. If this is for a product (as 
opposed to a proof-of-concept or research project) then I would strongly 
recommend that you work with us - we can help you make the port and provide 
support afterwards.

> 3.    Also if I'm using uCLinux to implement, then it will be much more
> easier?
Working with uClinux will be easier than working with eCos insofar as uClinux 
comes with a bunch of device drivers etc which you may have to write 
yourselves if you use eCos. But from the point of view of a Java VM, there's 
not much difference; in many ways eCos is an easier target, because it has a 
nice threading API. Last time I looked at threading in uClinux, I found a 
very incomplete implementation of the pthreads library.

> 4.    Do you think it will be a problem for a MMU less processor to run
> Java, meaning the speed may be too low?
It depends on what you intend to do in Java. On embedded devices JIT 
compilation is usually not an option (it uses too much memory, and too much 
CPU to do the compilation), so most of your code is going to be interpreted. 
If you start thinking "once we have Java on our rice cooker, we can use it to 
play multi-user arcade games" then you are heading for trouble. But we can do 
quite impressive stuff on a 55 MHz ARM7TDMI.

> 5.    Is there any other Linux that may able to run Java with MMU less
> processor?
SFAIK uClinux is the only Linux variant that runs without an MMU, and also the 
only open-source, Unix-like kernel which is still actively maintained. There 
are other "Linux-like" commercial RTOSs which can run without an MMU - and of 
course there is eCos, but eCos != Linux.

This is getting a bit off-topic for this mailing list; you may wish to 
continue at least part of this discussion off-list.

Best wishes


-- 
Chris Gray                      /k/ Embedded Java Solutions
Embedded & Mobile Java, OSGi        http://www.kiffer.be/k/
chris.gray@kiffer.be                         +32 3 216 0369


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