From: cowan@mercury.ccil.org (John Cowan)
Subject: [TUHS] Need a new PDP-11 or VAX?
Date: Sun, 28 Apr 2013 01:57:33 -0400 [thread overview]
Message-ID: <20130428055733.GH24560@mercury.ccil.org> (raw)
In-Reply-To: <20130428035736.GA1001@bitmover.com>
Larry McVoy scripsit:
> Ideally with 32 bit ints, 64 bit longs, 32 or 64 bit pointers in the
> compiler, obviously more registers, and nothing like the vax.
Sounds right. I'm torn between the 8 addressing modes of the PDP-11 and
32 registers, or the 16 addressing modes of the Vax and only 16 registers.
In either case, 32-bit instructions allow all operands to have full
addressing mode on both source and destination rather than just a register
for one or the other. The byte/word bit of the memory instructions would
become 2 bits for byte/short/int/long. One issue is whether to have
a single 32-bit index in modes 6 and 7, or provide a full 64-bit index
with two trailing 32-bit words. Branches can have much bigger offsets,
which is good.
The FPP needs a complete overhaul: it should look pretty much
like the main ISA, and of course use IEEE format operands. Hmm,
perhaps get *really* modern and use 3 bits of size for byte/short/
int/long/float32/float64/decimal64/decimal128, where the last two are
IEEE 754:2008 decimal floating point values.
> I'm too dumb to get it but I never warmed up to the vax.
When I saw it had 256 opcodes I knew I was never going to master it, no
matter how orthogonal it was. (I came from the PDP-8 to the PDP-11.)
Little did I know the Last ISA would have thousands and thousands of
opcodes!
--
Note that nobody these days would clamor for fundamental laws John Cowan
of *the theory of kangaroos*, showing why pseudo-kangaroos are cowan at ccil.org
physically, logically, metaphysically impossible. http://www.ccil.org/~cowan
Kangaroos are wonderful, but not *that* wonderful. --Dan Dennett on zombies
next prev parent reply other threads:[~2013-04-28 5:57 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-27 21:26 Dave Horsfall
2013-04-27 22:41 ` Larry McVoy
2013-04-27 23:53 ` Dave Horsfall
2013-04-28 0:12 ` Ronald Natalie
2013-04-28 1:39 ` John Cowan
2013-04-28 3:38 ` Nick Downing
2013-04-28 3:48 ` Larry McVoy
2013-04-28 3:57 ` Larry McVoy
2013-04-28 5:57 ` John Cowan [this message]
2013-04-28 5:34 ` [TUHS] curmudgeon credit Aharon Robbins
2013-04-28 7:08 ` Nick Downing
2013-05-14 6:11 ` Aaron J. Grier
2013-05-14 6:52 ` emu
2013-05-14 7:51 ` David Evans
2013-04-28 16:28 ` Larry McVoy
2013-04-28 7:45 ` [TUHS] Need a new PDP-11 or VAX? Peter Jeremy
2013-04-28 10:50 ` Ronald Natalie
2013-04-28 0:15 ` Ronald Natalie
[not found] <mailman.3.1367200802.17183.tuhs@minnie.tuhs.org>
2013-04-29 23:19 ` David Barto
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