PRO-380 (was: Russian PDP11 CPU chips on ebay...)
bqt at softjar.se
Wed Jan 21 11:35:42 CST 2009
Paul Koning <Paul_Koning at Dell.com> wrote:
>>>>>> >>>>> "emu" == emu <emu at e-bbes.com> writes:
> emu> Quoting Gordon JC Pearce MM3YEQ <gordonjcp at gjcp.net>:
> >> http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=12036621970
> >> Two things I wonder about: How many has he got, and how hard would
> >> it be to make an SBC-6120-alike for the -11 with that?
> emu> What's wrong with the original J11's ? I think they look even
> emu> nicer than the black ones ...
> emu> And then you could make something like a PRO-385 ;-)
> Wouldn't it be a PRO-380? Well, unless you can clock it at 20 MHz
> which was the original plan for the 380, but the J-11 failed to
> deliver so they ended up at 10.
I think he might have meant PRO-385 as an improvement on the PRO-380...? :-)
However, the J11 originally didn't deliver the planned 20 MHz, but it
sure delivered more than 10 MHz. The reason the PRO-380 stayed at 10 MHz
anyway was because the support chips DEC used for the PRO couldn't
handle higher speeds. So even though the J11 could deliver atleast 15
MHz (which is what the 11/53 and 11/73 uses) and probably 18 MHz (which
is what later 11/73 and the 11/8x use), the PRO (unfortunately) stopped
at 10 MHz (which you can't blame on the J11). Even worse (I think) is
that P/OS never supported split I/D space, nor supervisor mode, so the
PRO makes very little use of the J11 cpu.
(The 11/9x machines eventually used 20 MHz J11 cpus.)
> Note that making a PRO-38x means you have to reverse engineer the I/O
> control gate array and the video hardware, both of which are likely to
> be serious exercises in masochism. (Why reverse engineer the most
> bone-headed I/O design in the history of DEC?) Either that, or a lot
> of discrete parts to make a PRO-350 clone.
I couldn't agree more. :-)
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