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Re: The power of the original PDP11 (20, 10) but for only tuppence! [message #287502 is a reply to message #287501] |
Fri, 10 April 2015 09:43 |
bill
Messages: 165 Registered: December 2011
Karma: 0
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Senior Member |
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In article <mg8j8r$r3a$1@iltempo.update.uu.se>,
Johnny Billquist <bqt@softjar.se> writes:
> On 2015-04-10 13:52, gareth wrote:
>> http://ww1.microchip.com/downloads/en/DeviceDoc/70157D.pdf
>
> Oh, c'mon. You can't just go around and claim that any 16-bit CPU is a
> PDP-11...
>
> And as far as "power" goes. That depends on how you measure things.
> The Microchip have a larger address space than any PDP-11, but on the
> other hand, it does not have an MMU, as far as I can tell... Nor FP
> hardware.
>
I kind of got the idea he was hinting at Microcoding a PDP-11 on top
of one of those PICs. Pretty sure that has already been done. Once
I retire (again) this June I hope to learn VHDL and do some playing
with stuff like that on the development kits I have. Still may get
the chance to try out some of the extensions I thought would have
worked well on the PDP-11.
Oh yeah, and being as I have given up on any hope of the PDP-11 OSes
(in particular RSTS) ever being released I think I will take a serious
look at writing a clone. :-)
bill
--
Bill Gunshannon | de-moc-ra-cy (di mok' ra see) n. Three wolves
billg999@cs.scranton.edu | and a sheep voting on what's for dinner.
University of Scranton |
Scranton, Pennsylvania | #include <std.disclaimer.h>
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Re: The power of the original PDP11 (20, 10) but for only tuppence! [message #287933 is a reply to message #287749] |
Thu, 16 April 2015 09:38 |
Lawrence Statton
Messages: 326 Registered: May 2013
Karma: 0
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Senior Member |
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Walter Bushell <proto@panix.com> writes:
> In article <mg8j8r$r3a$1@Iltempo.Update.UU.SE>,
> Johnny Billquist <bqt@softjar.se> wrote:
>
>> On 2015-04-10 13:52, gareth wrote:
>>> http://ww1.microchip.com/downloads/en/DeviceDoc/70157D.pdf
>>
>> Oh, c'mon. You can't just go around and claim that any 16-bit CPU is a
>> PDP-11...
>>
>> And as far as "power" goes. That depends on how you measure things.
>> The Microchip have a larger address space than any PDP-11, but on the
>> other hand, it does not have an MMU, as far as I can tell... Nor FP
>> hardware.
>>
>> Johnny
>
> Well FP hardware is a mere matter of speed. Some chips without FP
> hardware are faster at FP than some with. Example, 68040 without FP
> was faster than the predecessor 68030 with FP hardware.
Yeah, but part of that was the spectacular cycle-count for martialling
the CPU state onto the stack for the coprocessor "interrupt" ... Even on
the straight 68000, an A-line or F-line trap/rti had something like 30
cycles of overhead, and the larger (more CPU state) chips only got worse
and worse.
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