><>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;
>
>Huh? a PDP11 emulator for alpha would be written as PAL to get the best
>results. Caching it is pointless as it's still a 16bit machine and
>would still flog itself to death trying to manage a data file greater
>than fits in ram (4mb max on PDP11 and some of that would be code!).
You misunderstand. I'm not talking about caching any PDP-11 code or data,
just the Alpha code which executes the emulator. Any memory fetch which
fetches Alpha code is overhead; a real PDP-11 wouldn't have to make that
memory fetch. If you can build a PDP-11 emulator small enough to fit in the
primary cache, all of your memory fetches can be payload.
It wouldn't really be PAL code because it would be executing in the chip's
boot environment; loaded from SROM into primary cache and staying there.
It owuld have a lot of the characteristics of PALcode; the extra registers
which Palcode depends upon would be visible, the MMU would be off, etc., but
it wouldn't really be PALcode because it wouldn't be called by a PAL trap.
Roger Ivie
ivie(a)cc.usu.edu
> 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!
FWIW, it's been my experience that on problems small enough to be tackled
by the J-11, an 18MHz J-11 eats the VAX-11/780 for lunch.
Roger Ivie
ivie(a)cc.usu.edu
Can anyone here help them out? Please respond to them and not me.
Thanks.
-----
Date sent: Thu, 23 Apr 1998 14:37:31 -0400
From: Liz Huntley <lizh(a)cannet.com>
Subject: Laser, Pal286
A question if don't you mind?
I'm tinkering with a Laser, Pal286. A customer of mine uses it, it had
a HDD Controller Failure. It actually works pretty well when it's
working. I don't suppose you know where I could get a working
motherboard for it... which I'm guessing that it needs.
I appreciate any info.
Thanks, Liz Huntley
| o_ | \ _ _ o _ ._ _ Liz Huntley
|_|/_ |_/(/__> |(_|| |_> lizh(a)cannet.com
_| Canton, Ohio
-----
David Williams - Computer Packrat
dlw(a)trailingedge.com
http://www.trailingedge.com
On Apr 23, 13:14, Philip.Belben(a)powertech.co.uk wrote:
> First, thanks to Pete, Allison and others for explaining the PDP11-23
> stuff. I stand corrected, I suppose.
I just like to show off :-)
> A long running discussion. Allison, I don't understand how you can say
> that the PDP11, with its very simple instruction set, is _more_ CISC
> than (say) the 80286, with which you compare it here. To my mind the
> only really CISC feature of the PDP11 is the MARK instruction. I fear
> we may be talking at cross purposes, and may mean different things by
> RISC and CISC - could you give some specific examples, please?
I know that was directed at Allison, but I'd say that key features of RISC
architectures include large numbers of general registers,
one-instruction-per-cycle, and hardware decode rather than microcode, not
just the obvious minimised instruction set.
The PDP-11 architecture has only 7 GP registers (since you can't really use
the PC for just anything) but that's good for the times, and they really
are interchangable, so I'd be willing to argue that it wins on that.
It loses on the one-instruction-per-cycle, though. Instructions take
vastly different amounts of time to execute, depending on what they are,
and they're all several cycles long. Just think about the FP instructions,
or the Commercial Instruction Set. That's not the most CISC thing you've
ever seen? :-) At a more mundane level, the additions of instructions
like ASH is pretty CISC -- in fact the whole idea of extending the
instruction set by altering or adding to microcode is the essence of CISC,
and the antithesis of a Reduced Instruction Set Computer.
And of course it loses on the microcode vs hardware decode.
> For those who think a souped up PDP11 could be a pentium killer, bear in
> mind that there was a 32 bit PDP11. I don't mean the VAX, and I don't
> mean the PDP11-68: I mean the Motorola 68000. AFAICT the two
> architectures are very, very similar. Is it a Pentium killer? The
> 68070 might have been but it's rather faded away now...
Similar, but in many ways quite different. I just had this argument (from
a somewhat different point of view) on another mailing list. The 68K is
much more like a PDP-11 than anything else, but it has a lot of clutter
added.
That's my third of a tanner.
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
<Allison Parent wrote:
<
<> 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
<
<A long running discussion. Allison, I don't understand how you can say
<that the PDP11, with its very simple instruction set, is _more_ CISC
<than (say) the 80286, with which you compare it here. To my mind the
<only really CISC feature of the PDP11 is the MARK instruction. I fear
<we may be talking at cross purposes, and may mean different things by
<RISC and CISC - could you give some specific examples, please?
The CISC features are in the use of general registers (no specific
accumulator) and a huge assortment of addressing modes in many cases
featuring two operand addresses. Most micros are either single address,
primary accumulator and loaded with specific registers. Think of one
micro that would permit PC relative addressing and stack relative. I
happen to know two but they are not common.
Compared to most RISC machines the PDP-11 is very CISC. Also at the
time of the PDP-11 RISC had a specific definition that the -11 clearly
didn't come close to. The definition of the era was all instruction
would execute in 1 to to clocks, register rich and very simple
instructions fast instructions compared to complex many clocks to execute
instructions. The idea of auto index deferred (*x++) is not a RISC concept
as it's far to complex to execute in one or two clocks(minimum of two to
three memory reads and one write).
Opinion: PDP-11 of all 16bit machines of wide spread use was the best
suited for C programming or FORTH due to it's stack archecture and
addressing modes. The only 16 bit machines that can beat it for code
density are a few of the byte instruction oriented machines using far
larger and more complex compilers.
<For those who think a souped up PDP11 could be a pentium killer, bear in
<mind that there was a 32 bit PDP11. I don't mean the VAX, and I don't
<mean the PDP11-68: I mean the Motorola 68000. AFAICT the two
<architectures are very, very similar. Is it a Pentium killer? The
<68070 might have been but it's rather faded away now...
Sorry, the moto is similar in that it borrows some concepts. It lacks
the general resgister archecture, misses the idea of orthoginality and
is a primary accumulator machine. It's at best PDP-11 on bad acid. It
could be a pentium killer as the 680xx was a 32bit machine from day 0.
The VAX is the closest machine to the PDP-11 in general archecture and
instruction set of the lot. I has has compete for years against the X86
machines for a number of years not by surperfast clock numbers but the
ability to manage memory and large numbers of users. The VAX 7000m7xx
series with the NVAX-5(circa 1994) chip was already killing anything
Intel would produce for a few years. People are not junking 7000series
machines over Pentium yet!
A far closer machine is the NS16032, still 32bits but borrows more on
PDP-11 and VAX then moto did.
Even the z8000 was more like PDP-11 than MOTO! It did keep the registers
more or less general, had most of the addressing modes and most all were
applicable to the general registers.
In the intel race there can be lots of competitors as some of the "big
box" systems have far better IO and DISK systems than are married to
most pentium class machines. In the end if you munging gigabyte data
bases raw cpu speed is only a partial solution if your waiting for the
disk!
Allison
On Apr 23, 5:52, Daniel A. Seagraves wrote:
> Subject: More RSX weirdness...
> Last night I stared at the halted 83 for a while.
> RSX-11M V4.1 BL35C 256.K MAPPED
> SAV -- Cannot find home block
>
> Then it smacked me like a ton of bricks: The high 4K of a PDP-11 is I/O space!
> I had 252K or RAM! So, I rebuilt RSX11M.SYS that way. It worked.
> I was able to hardware-boot the RL02.
> So, I reinstalled my RQDX3, loaded RT-11, said COPY DL0:/device RSX11M.DSK/file
> to make an image, Kermitted it to the PC (2:30 transfer time!) and loaded it
> into the emulator. Now, with the Supnik emulator set for 2M or RAM (Just like
> the 83...), I'm staring at the same screen, while booting. SAV can't find
> the home block. Same thing for E-11. But everything works just fine from
> the hardware.
Well, I'm at a loss as far as the emulators are concerned. I've used them
precisely once, and that was only with RT-11. I'm glad you got the rest working,
though, and I hope my imperfect memories helped rather than confused.
> Oh, and it says most of the TTs and the DU don't exist while
> booting. Which makes sense, they don't...
That might mean you can't use them at all. For some devices, if RSX can't find
the hardware during the boot, it disables the driver. There may be some clever
way to persuade it to re-enable them if you need to, but I don't know. So I
hope you mean that those devices really aren't physically present!
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
I haven't got time to type loads of messages. These are in a roughly
random order.
First, thanks to Pete, Allison and others for explaining the PDP11-23
stuff. I stand corrected, I suppose.
Tony Duell wrote:
> BTW, does anyone know the position on reverse-engineered schematics? Who
> owns the copyright on those? The original company, the person/company
> who drew them out, what? Or are they just plain illegal (I doubt the
> latter, as I've seen them advertised as such for devices where original
> manufacturer's manuals are not available).
AFAIK, you both do. You own the copyright in the diagram you've drawn
out, and the original designer/manufacturer owns the copyright in the
circuit it represents. So if I want to copy it I need permission both
>from you and from the designer. (It's like if I want to photocopy a
book I need permission from both the author and the publisher.)
Allison Parent wrote:
> 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!
A long running discussion. Allison, I don't understand how you can say
that the PDP11, with its very simple instruction set, is _more_ CISC
than (say) the 80286, with which you compare it here. To my mind the
only really CISC feature of the PDP11 is the MARK instruction. I fear
we may be talking at cross purposes, and may mean different things by
RISC and CISC - could you give some specific examples, please?
For those who think a souped up PDP11 could be a pentium killer, bear in
mind that there was a 32 bit PDP11. I don't mean the VAX, and I don't
mean the PDP11-68: I mean the Motorola 68000. AFAICT the two
architectures are very, very similar. Is it a Pentium killer? The
68070 might have been but it's rather faded away now...
Just my half groat's worth again!
(Yes, Tony, half a groat == tuppence == two pence == two pennies = (in
some sense) $0.02, which seems to be the value most people set on their
opinions here. About right in most cases (no offence intended))
Philip.
On Apr 22, 19:50, Daniel A. Seagraves wrote:
> Subject: Another RSX good one,,,
> OK, Now I can make myself an rsx11m.sys, VMR is, BOOt it, but when I
say
> SAV, it runs for awhile, types "CAN'T FIND HOME BLOCK", and halts.
Hmmmm... What are you trying to SAV this onto? The message means just
what it says. Sounds like you have an unformatted disk, or a disk error,
which might be due to corruption, or a hardware fault, or the disk isn't
online and writable, or you mistyped the disk specifier. What was the
prompt you got just before you typed SAV?
> It also complains about having to reduce partitions to the soze of the
> common area (?),
"VMR -- Partition reduced to executive common size", yes? This is just
for information. It's telling you that VMR has just installed an
executive common block in the appropriate partition, and eliminated some
unused space at the top of the partition. Executive is RSX-speak for
what unix buffs call the kernel, and what some other OSs refer to as the
monitor. A common block is a shared area, ie one that's not duplicated
for multiple instantiations of <whatever>.
> and the TT: driver is bigger than 4K.
That's just informative, not normally a problem. The RSX TT: driver is
quite big if it has many options enabled, and this is a common message.
> What've I done? I just switched DY and DL in the sysvmr.cmd file,
> and removed DU (The driver is corrupted...)
> -------
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
Last night I stared at the halted 83 for a while.
RSX-11M V4.1 BL35C 256.K MAPPED
SAV -- Cannot find home block
Then it smacked me like a ton of bricks: The high 4K of a PDP-11 is I/O space!
I had 252K or RAM! So, I rebuilt RSX11M.SYS that way. It worked.
I was able to hardware-boot the RL02.
So, I reinstalled my RQDX3, loaded RT-11, said COPY DL0:/device RSX11M.DSK/file
to make an image, Kermitted it to the PC (2:30 transfer time!) and loaded it
into the emulator. Now, with the Supnik emulator set for 2M or RAM (Just like
the 83...), I'm staring at the same screen, while booting. SAV can't find
the home block. Same thing for E-11. But everything works just fine from
the hardware. Oh, and it says most of the TTs and the DU don't exist while
booting. Which makes sense, they don't...
-------
I received this email, if any one in Australia is interested contact
the party below, not me.
--------------------
Date sent: Thu, 23 Apr 1998 14:59:51 +1000
From: Alex Roche <alexr(a)amfac.com.au>
Organization: Amfac Pty Ltd
Subject: Honeywell Bull
Hi,
I have a Honeywell Bull X-Superstream.
Know any one in Sydney Australia (where I am) or elsewhere who wants
to buy one for a song?
Alex Roche
-----
David Williams - Computer Packrat
dlw(a)trailingedge.com
http://www.trailingedge.com
