Re: Tempest board rev.

Thanks for your great explanation. I now understand how the A11 inflicts the use
of 1 or 2 K windows, thereby enabeling the use of the 2532. Probably this is
also the reason why they ever made a 2532, as opposed to the 'regular' pinned
2732...

TTYL!

John Robertson wrote:
>
> Ah, well, it is fairly simple once you understand the addressing. On your
> board, there are, say for simplicity two 2716's. Now the hardware person
> was a bit creative and wanted to take advantage of the cheaper 2532's (when
> they become available - remember this is 1980ish)) and hardwires the board
> so that the first socket has A11 as the chip enable for the 1st 2716, and
> inverts A11 to use as the chip enable for the second 2716. Now when you use
> the chip select you have it cover a 1K window instead of 1/2K and for the
> first half of the 1K A11 is LOW thus 2716 #1 is enabled and 2716 #2 is
> disabled because it sees inverted A11 or HIGH. Now for the upper half of
> the 1K window, you then toggle A11 high, this disables 2716 #1, and enables
> 2716 #2. Now when the 2532's drop in price to rival the 2716's you just
> drop them in, they program faster and fewer assembly steps for the
> manufacturer. Or if 2716's aren't available or whatever...
>
> On your Tempest they just had a bunch of 2716 sockets that were wired to
> A11 and the second bunch wired to inverted A11, thus when you stuff in the
> 2532's, you just use the first bunch with regular A11.
>
> You will see some games that had jumpers in place that would allow you to
> run MANY different types and sizes of ROM memory - Midway motherboards
> spring to mind as an example, plus Bally pinball MPU's.
>
> Clear?
>
> John :-#)#
>
> At 12:59 PM 4/1/2000 , Tek wrote:
> >Yes, but how does the board know? Probably I'm being stoopid, but I still
> >cannot
> >see it?
> >
> >Cya !
> >
> >John Robertson wrote:
> > >
> > > If your version is using 2532's, then the A11 of the 2532 is the old
> > > ChipSelect on the 2716, which was often A11 (like Pacman, Tempest and other
> > > games)
> > >
> > > John :-#)#
> > >
> > > At 09:12 AM 4/1/2000 , Tek wrote:
> > > >Hi guys-
> > > >
> > > >I was wondering, is a newer Tempest board with only half of the ROMS
> > different
> > > >from the 'normal' one?
> > > >
> > > >As far as I could see the address decoder is still the same, but how
> > does it
> > > >know the data of each second
> > > >ROM is in the first location?
> > > >
> > > >Cya !
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> John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
> Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
> http://www.flippers.com
> "Old pinballers never die, they just flip out."
>
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Received on Sun Apr 2 07:57:22 2000