The '289's are inverting, though tristate, just like the '189's. TI made a '219
which was a noninverting tristate version of this same sort and pinout. ISTR
that there was yet another part, albeit not of the normal 74xxx sort, that was a
non-inverting version as well, but I can't, for the life of me, rememberit
(senior moment). These days, it's both cheaper and easier (faster, too) to use
a CMOS ram of considerably larger size.
Dick
----- Original Message -----
From: "Ben Franchuk" <bfranchuk_at_jetnet.ab.ca>
To: <classiccmp_at_classiccmp.org>
Sent: Thursday, November 01, 2001 5:17 PM
Subject: Re: classiccmp-digest V1 #761
> ajp166 wrote:
> >
> > Those parts were never cheap!
> >
> > You can also use 74289s for the '189s. The '382s are an improved version
> > of the '182. A note, if you can tolerate a slower ALU you can omit the
> > '382s
> > and just use ripple carry.
>
> If the 74289's are the non inverting 16x4 rams I would use them. I plan
> to use 74ls382's (the ripple carry alu's).
>
> > A sub for 74189s is some of the byte wide cache rams from an old 386/486
> > PC as the faster ones were faster than the TTL 74189! You dont have to use
> > the full space of the cache ram though having it would make afor an
interesting
> > register array.
>
> Can't do that for three reasons
> 1) I am use a 16 x 12 ram ( 3 chips ) on two boards for a 8 x 24
> register array.
> 2) I am using the 486 cache chips as main memory in my FPGA prototype
> 32k x 12 bits.:)
> 3) This was a TTL design on paper of what a computer designed in the
> early 1980's
> could have been like. That rules out 2901 bit slices.
>
> > Allison
> As it stands today I have a FPGA ( pat pat pat ) that is configured to
> have a similar
> layout as the ttl design and this lets me play around with the
> configuration. Mind you a
> larger TTL CPU with lights and switches is more impressive. If you like
> lights
> and switches here is a neat link http://www.angelfire.com/scifi/B205/
> 'to the Bat Cave'
>
> Ben Franchuk.
> --
> Standard Disclaimer : 97% speculation 2% bad grammar 1% facts.
> "Pre-historic Cpu's" http://www.jetnet.ab.ca/users/bfranchuk
> Now with schematics.
>
>
Received on Fri Nov 02 2001 - 10:02:13 GMT