TTL computing

From: Allison <ajp166_at_bellatlantic.net>
Date: Tue Apr 9 23:16:21 2002

some items sorta conspired to drive cpus to multiples of 8bits.

 ASCII chars
 width of data paths internal to MOS cpus early on.
 byte wide memories, especially rom/prom/eprom

Personally I like either 18 ot 24 bits and have thought that
the PDP-8 with the right side (address portion) of the word
stretched to 18 bits or better yet 24 would be a nice machine.

24bits is majik as it's a multiple of 8.

PDP-8 addressing as 24bit 524288 word page, current and
          also there is page 0 addressing! A field would be
          16MB. EMA would not be needed.

Allison

-----Original Message-----
From: Ben Franchuk <bfranchuk_at_jetnet.ab.ca>
To: classiccmp_at_classiccmp.org <classiccmp_at_classiccmp.org>
Date: Wednesday, April 10, 2002 11:21 AM
Subject: Re: TTL computing


>Richard Erlacher wrote:
>
>> 12-bit CPU's out there ??? Everybody knows that 12-bitters haven't
existed
>> since the '70's! After all, they stop existing on the day the last one
is
>> shipped. The device manufacturers stop considering a market as viable
once
>> the potential for 100K pieces per week per manufacturer is no longer
there.
>
>True about manufacturing, but I wish one had more choice with computer
>hardware/software for the PC user.I think DEC sold the PDP-8 until about
>1990. Since I can't find a 12/24 bit CPU that I like I am building my
>own. A 12/24 bit cpu chip could have came out around 1980 with the
>8086/6800. Part of the challenge in the cpu design I am doing in FPGA is
>to have it emulate (for the most part) a fictional 12/24 bit cpu in a 40
>pin dip.The last thing I added was a 8 bit refresh counter for dynamic
>memory and a single channel DMA for a floppy. Running at 4.9152 Mhz (
>800 ns memory access, 512Kb of ram ) I hope the Squash the XT market in
>1983!. :)
>
>--
>Ben Franchuk - Dawn * 12/24 bit cpu *
>www.jetnet.ab.ca/users/bfranchuk/index.html
>
Received on Tue Apr 09 2002 - 23:16:21 BST