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To: python-list@python.org
From: Roel Schroeven <roel@roelschroeven.net>
Subject: Re: Feedback on my python framework I'm building.
Date: Mon, 15 Oct 2012 19:29:56 +0200
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MRAB schreef:
> On 2012-10-14 23:38, Dave Angel wrote:
>> On 10/14/2012 08:48 AM, Roy Smith wrote:
>>> In article <507a3365$0$6574$c3e8da3$5496439d@news.astraweb.com>,
>>>  Steven D'Aprano <steve+comp.lang.python@pearwood.info> wrote:
>>>
>>>> Remember using PEEK and POKE commands with BASIC back in
>>>> 1978? Pretty much impossible in Python.
>>> But, trivial to implement as an extension :-)
>> PEEK and POKE were intended to be used with memory mapped devices.
>> Simplest example is the 6502 chip, which had no I/O bus -- it was all
>> memory mapped.  Want to change baud rate?  poke a byte somewhere.
>>
>> These days, the only device I can think of that's usually memory mapped
>> is the video.  And few programs talk to it that way.
>>
>> Now, INP and OUT (or various similar names) were for doing port I/o.
>> But I suspect that modern systems aren't going to let you do much of
>> that either.
>>
> It depends on the CPU. Some have specialised instructions for I/O,
> others don't.

I think Roy Smith meant that the OS on modern systems generally prevents 
direct access from user space to either memory mapped I/O or port mapped 
I/O. Embedded systems might allow direct access, but AFAIK Python 
doesn't run on those.

Best regards,
Roel

-- 
"Too often we hold fast to the cliches of our forebears. We subject all
facts to a prefabricated set of interpretations. Too often we enjoy the
comfort of opinion without the discomfort of thought."
         -- John F Kennedy

roel@roelschroeven.net