1 Jan
2006
1 Jan
'06
11:04 p.m.
William Maddox wrote:
For easy-to-decode, I can't think of anything that gives you as much
power for as little work as the DG Nova. The Nova encoding, however,
is very closely tied to a model datapath, as the arithmetic, logical,
and shift instructions are encoded like the so-called
"microinstructions" of the PDP-8. Most bits in the instruction
correspond directly to control signals without any encoding at all.
On the other hand, the Nova datapath is relatively straightforward to
implement in TTL.
But looking at the schematics it also makes full use of 74172's , 8 x 2
dual port ram.
In fact someone sent me some 74172's but they got lost in the mail. :(
The lack of real hardware like TTY's and Core memory made up of so much
of the early
processors I/O that a full emulation is not possible. Lack of full
documention is the other
problem. My pdp-8 handbook covers TAD quite well, extended options for
hardware
multiply , or divide it does not. I could cheat and see what Simh does. :)
--Bill
Ben alias Woodelf
PS. Since CPLD's now are 3.3 volts I can use ferro-ram memory after
getting a design
working @ 5 volts and standard memory.