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Username: Peter
Realname: Peter vandervos
About me:Programmer on RISC OS and Windows, ARM, 8051 and AVR since 1987
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Comments posted:17 (show all)

Recent comments

On RISC OS Open: One year on:

In reply to Jwoody: I indeed have an other view on using Linux on an embedded ARM system, maybe because I use it.

For me, the most important thing is control. I want to have control over the system. I/O block: don't need it. You can just as easy write a simple loop to check things without blocking and you have more control over it. Debugging is simpler too. Multitasking is a pain. I know when my tasks can wait some time and don't want the OS to decide it. Getting a system to run at it's maximum speed is easier on RISC OS. But the most annoying thing is writing device drivers. In RISC OS I normally write a module in assemble but you can use C to. You can use most of the features of the OS using swi's. Using Linux you write a kernel module. You can only use a restricted subset of OS calls and the most annoying thing is the memory protection. You can not easily access user memory from a kernel module and kernel memory from user space. And you have to link it to the kernel which takes a lot more time.

All the unix features like multitasking, virtual memory, blocking I/O are great on a multi user system running different tasks but on an embedded system I'll have RISC OS any day.

Peter V

 is a RISC OS UserPeter on 01/08/07 09:42AM
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On ROS fan loses Acorn domain in dispute:

Castle doesn't make A7000 computers any more. About a year ago they stopped making them. Problems with components or something like that. We realy needed A7000 computers thats why we got the last 4 of them, but without a case.

Peter V.

 is a RISC OS UserPeter on 13/09/06 11:58AM
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On Wakefield 2006 live news:

Re JWoody: What you see is that slow I/O (serial port/MIDI/DMX, Keyboard, Sound, network etc) uses buffers/interrupts. Faster processes (Disk/Screen) don't.

So what happens when a new font has to be cached, millions of cycles are waisted when the head of the harddisk seeks the right track (a small delay when printing to the screen). Under interrupt, the slow processes keep on running.

But who will finish the printing to the screen first? The pre-emptive system has to wait until the other interrupts are finished. The co_op system continues at ones (OK, I know, you can not see the difference it is late half a milion clock ticks but for time critical systems it can make a difference).

Peter V

 is a RISC OS UserPeter on 14/05/06 10:54PM
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On Wakefield 2006 live news:

Re JWoody: You simplify to much. In Risc OS, the main application gives control to an other application when it calls Wimp_Poll, correct. But, like you wrote, interupts can happen and guess what they are used for: I/O. You don't write to a serial port, you write to a serial port buffer. You don't read from a serial port, you read from a serial port buffer. If there's nothing there what do you do. You wait, but I give control to Wimp_Poll and check again when it returns.

The difference is, you write your programs in an other way. You don't use blocking calls.

Peter V.

 is a RISC OS UserPeter on 14/05/06 10:09PM
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On Voice-over-IP on RISC OS: What's involved?:

adrianl: But audio doesn't have to relies on CallBacks. If you install a voice module you get an interrupt when the buffer needs to be filled. If you also have a module reading data from an internet socket under interrupt it could be done. Still a lot of work :-(

Peter V

 is a RISC OS UserPeter on 31/10/05 9:43AM
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