<>As the PDP-11 instruction set is MUCH better than 80x86, would it
<outrun
<>a PC? Could this be a Pentium Killer?
as it was in 1982-3 the PCversion of the PDP-11 aka PRO350 could eat
the XT and turbo XT for a snack. When the AT came around DEC popped
out the pro380 with the J-11 cpu...gulp, burp! ATs are tasty.
Competing against the mostly 16bit 8088/6 and the 286 the PDP11 was out
front. To match a 16bit cpu against a 32bitter... you must be inhaling!
Allison
After your done laughing remember this...
At the time the VAX was new in the market the PDP-11 group took most of
their standard 11/70 peices and cooked up the 11/74 which was a 4cpu SMP
11/70 and could eat vaxen(11/780) for snacks. That was it's demise...
there were only four working 11/74s built before that was crushed.
<Hmm, refresh my memory, now what were the PDP-11 instructions to
<directly address 4GB of memory? I can't seem to recall any 32 bit
<address registers.
Look in the VAX archectecture book.
<Darn. I've really lost it...how did the virtual memory hardware work in
<a PDP-11?
Nicely (again the vax is a mostly stretched 11).
<Seriously, if you mean the sorta RISC like instruction set in the 11 is
RISC?????? PDP-11 is the most CISC machine in the 16bit realm. What
other 16bitter is a two address orthoginal machine?
<better than the x86 set, then DEC probably would have come up with
<something like that. Course, with extra silicon, they could have gone
<to 64 bits, and put more cache onboard, then clock it really fast. Then
<come up with some catchy marketing name, like Gamma, or Beta, or ....
They did called it VAX and when it came time to outvax VAX then comes
alpha.
Allison
<Um... Am I way out here? Doesn't the 23 support 22 bit addressing? And
The basic M8186 early revs are 18bit but most work as 22bit, the later
revs were 22bit. That's assuming the backplane is wired for 22bit as
well.
<I never before heard of a 16 bit Qbus! ISTRT the F11 processor is
LSI-11/03 cpu and box. The backplane was wired for only 16bit addesses.
Also that particular CPU put some of the microcode signals on what would
have ben the A16-21 lines.
<settable between 18 and 22 bit (128KW, 256KB and 2MW, 4MB respectively).
<The 18 bit setting is used in the 23 on 18 bit Qbuses and in the 24 on
<unibuses. The 22 bit setting is used on 22 bit Qbuses, but you need
<extra hardware to use it in the 24 (i.e. on unibus).
Your thinking of latter machines with specific backplanes.
Allison
> What would happen if we made a PC-sized PDP-11 processor using the Alpha
> technology? (On a single chip, clock it at ~300-400 MHz)
> As the PDP-11 instruction set is MUCH better than 80x86, would it outrun
> a PC? Could this be a Pentium Killer?
I doubt it could be a Pentium killer, but I could be wrong. The RISC
machines get performance by making it difficult to go to memory; on the
PDP-11, it's much to easy to go to memory.
Take, for example, the PDP-8. The worst-case instruction on the PDP-8
could require as many as five memory accesses (hmm; I forget which one
took five. I only count four for ISZ I Z 10 (fetch 10, write incremented
value, fetch from incremented value, write incremented value pointed to by
incremented value) and three for JSR I Z 10 (fetch 10, write incremented
value, stash return address at location pointed to by incremented value),
so I could be wrong) each of which depend on the previous one. You're not
going to get hot performance out of that unless you decide that the main
memory can be built using a 5-port register file on the chip.
I've occasionally wondered about doing a tight hand-coded PDP-11 emulator that
fits in the primary cache of an Alpha. If possible, you'd be using the Alpha
essentially as a programmable microengine and programming it to be PDP-11.
The reason to fit it in the primary cache is because of how the Alpha boots;
at reset, it loads its primary cache from an external serial ROM and begins
executing it. If you could fit the emulator in the primary cache, you could
think of the Alpha+SROM as a PDP-11 microprocessor.
Roger Ivie
ivie(a)cc.usu.edu
Seth and Pete were discussing the PDP11-23...
>> 2) Same as above, but for the M8044-DB boards. I could put one
>> of these in with the M8047's to get a full 64Kword of RAM, yes?
>> Does anyone know what the DIP-switch settings for these boards
>> are?
>
> Yes, but I'm not sure why you say "full" and 64Kword" together :-)
> 32KW (64KB) is the limit for 16-bit addressing, or 128KW (256KB) for 18-bit
> addressing. Ignoring the I/O page, that is.
Um... Am I way out here? Doesn't the 23 support 22 bit addressing? And
I never before heard of a 16 bit Qbus! ISTRT the F11 processor is
settable between 18 and 22 bit (128KW, 256KB and 2MW, 4MB respectively).
The 18 bit setting is used in the 23 on 18 bit Qbuses and in the 24 on
unibuses. The 22 bit setting is used on 22 bit Qbuses, but you need
extra hardware to use it in the 24 (i.e. on unibus).
Just my half groat's worth.
Philip.
On Apr 22, 1:57, Tony Duell wrote:
> Jack Peacock wrote:
> > 'No, I can do it with a normal 16 pin TTL chip that doesn't have to go
> > in a programmer first'. So, what was the chip ?
> >
> > 74LS138, 1 of 8 decoder, the three inputs go to A, B, C, all 8
> > possibilities decoded on the outputs.
>
> Alas not.. I didn't want the 8 separate combinations of the 3 input
> variables - I wanted a single output that was a complex function of them
> - something like A.C + A.B/ + A/.C/.B or something...
I thought of that too. Then you might be able to do it with an AOI package,
but I'd use a 156, which is a demultiplexer/decoder but with open-collector
outputs, which I'd wire-AND.
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
Sure. And then Apple would show our mascot, Barney, in flames.
I like this already!
>
>What would happen if we made a PC-sized PDP-11 processor using the
Alpha
>technology? (On a single chip, clock it at ~300-400 MHz)
>As the PDP-11 instruction set is MUCH better than 80x86, would it
outrun
>a PC? Could this be a Pentium Killer?
>-------
>
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<are there any good sites out there containing collections of schematics
<for old machines? I occasionally come across sites with a few schematics
No.
<interest in this? I was thinking more along the lines of some of the
<more obscure hardware out there though, as there's probably plenty of
<places to get details on common machines such as the popular 8-bit
<micros of the early 80's. Would be nice to have copies of ROM/Disk
<images where possible too...)
There is the problem of copyrights and permission. Not as easy as you'd
think as the copyright live past the companies demise so you have to
track where or who still holds it.
Allison
As the PDP-11 instruction set is MUCH better than 80x86, would it outrun
a PC?
-------
Hmm, refresh my memory, now what were the PDP-11 instructions to
directly address 4GB of memory? I can't seem to recall any 32 bit
address registers.
Darn. I've really lost it...how did the virtual memory hardware work in
a PDP-11?
Seriously, if you mean the sorta RISC like instruction set in the 11 is
better than the x86 set, then DEC probably would have come up with
something like that. Course, with extra silicon, they could have gone
to 64 bits, and put more cache onboard, then clock it really fast. Then
come up with some catchy marketing name, like Gamma, or Beta, or ....
Jack Peacock
I have C-64 ones. You could attach a gender changer to the koala
pad if it has an Apple plug, and use it on a Commodore.
>Does anyone have the disks for the paint program that came with the
Apple
>Koala pad?
>
>Thanks
>
>manney(a)lrbcg.com
>
>
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