Re: Gottlieb RAM question

What speed 6116 chips are you using? I can't find a Krull schematic, but Mad Planets
used 6116LP-4 RAMs, which are 200 nS parts. Even then they still use one 4801 as a
background video buffer. That must have been a damn fast RAM, they "clock" the write
line with the H0 line! To do that the speed must have been in the under 100 nS area.

Tom McClintock wrote:

> OK, three weeks later and I finish my experimenting. I robbed one good MK4801 off
> another Gottlieb board so I can test a single 6116 instead of two and doubling my
> potential problems.
>
> I lifted pin 19 and tied it to +5 (pin 24 of the 6116). Didn't work.
> Tied pin 19 to GND (pin 12 of the 6116). Didn't work.
> Tried Roger's suggestion of tying pin 19 to another select line (pin 23 in this case)
> - still didn't work.
>
> At this point can I safely assume the Gottlieb board doesn't like the extra 8K in the
> 6116? Suggestions?
>
> tom
>
> solarfox@texas.net wrote:
>
> > On Sun, 13 May 2001 20:01:35 -0500, you wrote:
> >
> > >Quite interesting. So the MK4801 was the cheaper alternative to a 16K ram - even
> > >though it was technically the same chip. Hmm.
> >
> > Not at all uncommon - and actually, the MK4801 was an alternative to an
> > 8K RAM, not a 16K RAM, since half of the matrix was defective. :)
> >
> > >Well, I took a look through some Gottlieb schematics, and it seems that both 4801
> > >SRAMs have pin 19 labeled as "L" with a bar over it. Am I assuming correctly that
> > >this means logic Low?
> >
> > Afraid not... it means a signal called "L-not"; i.e. a signal called
> > "L", which is active when low instead of high. What "L" means is anyone's
> > guess, unless you have the data sheet...
> >
> > >Following the traces on the board, it appears each pin is connected to another
> > >device (the schematics only show a connection to a resistor). I know I'm showing
> > >my ignorance, but would I lift pin 19 on these 6116 RAMs and still have a
> > >functioning external circuit?
> >
> > Lift pin 19 on the 6116 chips _and_ tie it either to ground or to +5
> > through a 10K pullup resistor. (Tie each one separately; don't connect
> > them all to one pullup.) Don't leave it floating, or signal noise will
> > make the 6116 keep flipping back and forth between the two 8K banks
> > randomly.
> >
> > -----------------------------------------------------------------------------
> > "There is no virtue in suffering fools gladly, for it only encourages them to
> > persist in their foolishness." --Kehlog Albran
> > -----------------------------------------------------------------------------
> > solarfox@DON'TMESSWITHtexas.net (Gary Akins jr.)
> > http://lonestar.texas.net/~solarfox
> > -----------------------------------------------------------------------------
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Received on Fri Jun 08 03:16:15 2001