How were 32-bit minis built in the 70s/80?

[Dave Wade]

> -----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:
> > 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)
> 

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 


> 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.
>