On Apr 14, 14:44, Robert D. Keys wrote:
I am quite interested in the older unices, and
especially the potential
for home use on a smallish box of some sort. (Nostalgia trip, but why
are most of us here?)
Anyway, I was noticing the pdp-11 system 5/6/7
binaries and the freebie
sco licenses on Minnie, and was wondering where to go for info on how
to bring the things up. I saw one emulator for DOS? --- (neat way maybe
to use an old 4 meg dos box?). Can these things be made to run via
a 386/486 bootstrap and emulator, on something like a minix/aix/FreeBSD
sort of machine? I would expect something like a maintenance boot disk,
and a minimal file system to get the machine up and into the emulator
proper, might be feasible, maybe?
Yes, you want one of the emulator packages and a disk image for that. BTW, the
disk images I've seen don't have man pages, so you may want to download those
separately.
Also, I see pdp-11ish things in surplus around here
quite often.
What would be needed to cobble together a system, for a minimal system 7
sort of box to play with? If there were a list of required boards and
chassis for various levels of system, that might help a newbie get some
sort of machine together.
There are so many permutations, it's hard to make a list. There are two
general classes of PDP-11, QBus and Unibus. Most even-numbered models are
Unibus, most odd-numbered models are QBus (but not all). QBus machines tend to
be smaller.
As to operating system versions, 2.11BSD needs at least an 11/73 or 83 to run,
as it needs memory management with separate address spaces for instructions and
data. 7th Edition will also run on those machines, and if the kernel is
suitably compiled, will also run on smaller machines such as 11/23s, which are
quite common. Early versions will run on a whole range of models.
Whatever you get, you'll need a processor (which might be a single card or as
many as ten), memory (256K will do fine for 7th Edition, but more is better),
at least one serial line unit for a terminal (or PC with terminal emulation
software), and a disk controller with a suitable hard disk. Here again there
are lots of possibilities, you want at least 10MB for 7th Edition and a lot
more for BSD.
Others may wish to expand on what I've written. Personally, I'd go see what
you can find, describe it to the list, and wait for the 101 pieces of advice
you'll get from all of us about its suitability/desirability :-)
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
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From "Ed G." <edgee(a)cyberpass.net> Wed
Apr 15 13:09:26 1998
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Subject: PDP-11 Addressing Modes
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The first line of chapter on addressing modes in the *processor
handbook* states:
"In the PDP-11 family, all operand addressing is accomplished through
the eight general purpose registers."
If I understand correctly, even things like immediate operands and
addresses are represented as an addressing mode of a register, namely
the PC. I think this is quite cool.
What do people here on the list think of the flexibility and
generality of the PDP-11's addressing modes? Is this a well thought
out architecture in your view? How are the PDP-11's addressing modes
better or worse than those of other processors, past and present?
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From: "Ed G." <edgee(a)cyberpass.net>
To: pete(a)dunnington.u-net.com (Pete Turnbull)
Date: Tue, 14 Apr 1998 23:09:26 -0400
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Subject: Re: Floating Point-How Important
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References: "Ed G." <edgee(a)cyberpass.net> "Re: Floating
Point-How Important to Unix?" (Apr 10, 22:40)
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What about position-independent code?
Your query got me thinking about the various addressing modes
of the PDP-11 and how they might affect my brute force approach to
estimating floating point ops for C programs. Is this what you meant
when you asked about position independent code?
And yes, these addressing modes could mean the death knell for my
approach.
Index mode is definitely a problem as C programs seem to use r5 as a
frame pointer with both positive and *negative* 16 bit offsets (see
assembly language listing of my square root program below).
I don't think PC relative mode (e.g., clr addr) is a problem
(if the data segment follows the text, then the offsets would all be
positive and all less than the size of the program).
Is there such a thing as PC relative mode for the jmp op
code? In other words, can you make long + or -32K relative jumps on
the PDP-11? If so, this too could potentially confound my estimates.
.globl _absv
.text
_absv:
~~absv:
jsr r5,csv
~n=4
jbr L1
L2:clrf r0
cmpf 4(r5),r0
cfcc
jge L4
movf 4(r5),r0
negf r0
jbr L3
jbr L5
L4:movf 4(r5),r0
jbr L3
L5:L3:jmp cret
L1:jbr L2
.globl _mysqrt
.text
_mysqrt:
~~mysqrt:
jsr r5,csv
~n=4
jbr L6
L7:~g=177762
~err=177752
movf 4(r5),r0
divf $40400,r0
movf r0,-16(r5)
.data
L10000:77777;177776;177777;177777
.text
movf 4(r5),r0
divf L10000,r0
movf r0,-26(r5)
movf -16(r5),r0
movf r0,-(sp)
mov $L9,-(sp)
jsr pc,_printf
add $12,sp
L10:movf -16(r5),r0
mulf -16(r5),r0
subf 4(r5),r0
movf r0,-(sp)
jsr pc,_absv
add $10,sp
cmpf -26(r5),r0
cfcc
jgt L11
movf -16(r5),r0
mulf -16(r5),r0
addf 4(r5),r0
movf $40400,r1
mulf -16(r5),r1
divf r1,r0
movf r0,-16(r5)
movf -16(r5),r0
movf r0,-(sp)
mov $L12,-(sp)
jsr pc,_printf
add $12,sp
jbr L10
L11:movf -16(r5),r0
jbr L8
L8:jmp cret
L6:sub $20,sp
jbr L7
.globl _main
.text
_main:
~~main:
jsr r5,csv
jbr L13
L14:.data
L10001:77777;177776;177777;177777
.text
movf L10001,r0
movf r0,-16(r5)
~n=177762
movf -16(r5),r0
movf r0,-(sp)
jsr pc,_mysqrt
add $10,sp
movf r0,-(sp)
mov $L16,-(sp)
jsr pc,_printf
add $12,sp
L15:jmp cret
L13:sub $10,sp
jbr L14
.globl fltused
.globl
.data
L9:.byte 111,156,151,164,151,141,154,40,147,165,145,163,163,72
.byte 40,45,56,61,66,146,12,12,0
L12:.byte 147,165,145,163,163,72,40,45,56,61,66,146,12,0
L16:.byte 12,115,171,40,163,161,165,141,162,145,40,162,157,157
.byte 164,40,151,163,72,40,45,56,61,66,146,12,0
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