Core Memory Interfacing?

From: Peter C. Wallace <pcw_at_mesanet.com>
Date: Thu Apr 4 17:50:58 2002

On Thu, 4 Apr 2002, Tony Duell wrote:

> > > Except that every VT52 I've ever worked on used
> > > semiconductor memory, not core.
> > >
> > > Anyway. the fact that there's no microprocessor does not mean that
> > > there's no software. There are plenty of microcoded TTL designs about
> > > (the VT52 is one of them IMHO) which have PROMs containing something that
> > > is reasonably called firmware.
> >
> > Yeah, there is the old 7400 series arithmetic unit...
>
> The 74x181. I've used it many times. It's also used in many of the
> computers that I love (like the classic PERQs and the PDP11/45).
>
> >
> > But in my experience, most pre-micro computer
> > equipment used fusible-link ROMs for truth-tables;
> > a transitional item, the Processor Tech SOL's
> > keyboard, is a good example of this.
>
> Truely microcoded TTL-based designs are not uncommon. The VT52 is
> certainly one. So are some of the DECwriters IIRC (but I would have to
> check the prints to be sure). DEC seemed to love microcoded designs,
> actually...


Hytype IIs also use a 8 bit TTL based microcoded machine (IICRC they use
74LS283 adders, 74LS170 register file chips, along with bipolar PROMS)...

>
> It's difficult to know just where to draw the line between true
> microcoded designs and state machines with the combinatorial part of the
> logic in PROMs. In fact I don't think you can really distinguish between
> them.
>
> -tony
>

Peter Wallace
Received on Thu Apr 04 2002 - 17:50:58 BST

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