12 May
2019
12 May
'19
12:06 a.m.
-----Original Message-----
From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of ben via cctalk
Sent: 12 May 2019 01:48
To: cctalk at classiccmp.org
Subject: Re: How were 32-bit minis built in the 70s/80?
On 5/11/2019 5:14 PM, Warren Toomey via cctalk wrote:
They certainly thought that at Jodrell Bank, an outpost of the University of Manchester
http://www.jodrellbank.net/
in 1964 they started using Ferranti Argus 100 computers to control the radio telescopes.
http://www.computinghistory.org.uk/det/32443/Ferranti-Argus-100/
these were programmed in FORTH and the 24 bit word was ideal for storing astronomical
co-ordinates as sixed packed decimal digits.
So much so that when Ferranti stopped making the Argus 100 they created bit-slice
emulations of the machine using AMD2900 chips
I'm building my own 8-bit CPU from TTL chips,
and this caused me to think:
how were 32-bit minis built in the late 70s and early 80s? In
particular, how was the ALU built? I know about the 74181 4-bit ALU,
and I know (from reading A Soul of a New Machine) that PALs were also
used.
Did companies get custom chips fabricated, or was it all off-the-shelf
chips with a few PALs sprinkled in?
Thanks, Warren
8 bit computers are EVIL. REPENT DEAR BROTHER.
I WILL PRAY FOR YOU.
24 bit computers are HOLY AND DIVINE.
Building a 12/24 BIT CPU with 8 bit I/O.
(back on topic)
Early 70's computers other than IBM used TTL, and
fast core memory with
mostly a 16 bit word width. Other than the PDP 11, most computers where
adapted from the transistor era with tweaks added for banks of
memory.When the late 70's came around commercial customers had a large
main frame computer or small control computer from a few years earlier with
FAST TTL (S)logic, PDP 11's, IBM 360's or clones,or TTL standard/H like PDP 8
or NOVA computer.
Bit slice logic like the 2901 alu, (1975) would make for nice low cost 16/32 bit
cpu with byte load/store.
The market for 32 bit computers was decided however to sell FAST LARGE
systems (floating point/64K+ memory) like the VAX (S TTL) or upgrade other
designs like the NOVA computer with Custom or semi-custom (PAL logic)
logic.
INTEL being slow with the forgotten APX 432 design came out with 8086
leaving us with the defective CPU's of today.
The AMD2900 could be used to build 24 bit CPUs as well....
Ben's view point.
I am doing my computer with a FPGA development system for design logic
and testing and later using 2901's and LS TTL with 3 proms used for the
alu/control cards.
I have A nice 8/16/32 cpu design with 512KB of memory
(2901 alu )but I can't get it to route correctly. The 12/24 bit cpu just fits with
the FREE develpment software.
For a few K $ I can get the better version with being able route by hand my
logic to meet timing specs.
Once hardware SD card/serial port and software are working I then will port
the design to TTL.
I may need to write my own tiny langage to boot strap my system.
Ben.
Best of luck
Dave
PS:
16 bit computer format
[op 3..1][ac 3..1][mode 3..1][ix 3..1][aux][k 3..1] The tricky part is K is the
upper 3 address bits to extend 16 bit offset to 19 bits or a auto indexing
mode. This would be valid memory for the late 70's early 1980's but not for
today.