Re: Gottlieb RAM question

Roger,

Quite interesting. So the MK4801 was the cheaper alternative to a 16K ram - even
though it was technically the same chip. Hmm.

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?

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?

tom
p.s. for anyone that needs the Gottlieb schematics, they are up on my site:
www.ionpool.net

Rodger Boots wrote:

> As long as pin 19 is tied to either ground or +5 (or even one of the other
> address lines) it should work. Your board may not have the line connected.
>
> The MK4801 was actually a defective 16K RAM where pin 19 was hard tied
> internally to enable the good bank and was then sold as an 8K RAM. A totally
> good chip was sold as the MK4802. This was done in the early days of "large"
> RAM chips to keep from having to throw away a lot of the rejects. Some of the
> early IBM AT computers actually stacked two chips, one with a bad low half and
> one with a bad high half, as a low cost alternative to buying the scarcer
> fully-functional chips.
>
> Tom McClintock wrote:
>
> > I've got a Gottlieb Krull board which I inadvertently broken a pin off
> > of one of the SRAM chips. I guess I could solder on a wire, but I'd
> > rather just replace it with a new chip . However, these are the MK4801
> > (4118) 1,024 x 8 SRAMs (24-pin dip) which don't seem to be too common.
> > I can't seem to find them anywhere (at least not cheaply). And besides,
> > these Mostek chips are ALWAYS tarnished and corroded. There must be a
> > better replacement!
> >
> > I was examining one of my Bootleg Q*Bert boards, and sure enough, the
> > bootleggers replaced the Mostek MK4801 (4118) SRAMs with 6116s. Both
> > SRAMs are pin compatible with 2716 EPROMs, although the 4801s are 8K,
> > the 6116s are 16K. Great! So I replaced my ailing 4801s with the 6116s.
> > Doesn't work....
> >
> > So, I go back to the datasheets for both chips. The datasheet I have for
> > the 4801 shows pin 19 as "Ar" which is the select reference input. The
> > same pin on the 6116 is only labeled ôA10ö û an address input.
> >
> > Should I be lifting pin 19 on the 6116 and tie that to another pin
> > somewhere to get this SRAM to act like the 4801? Or can I even
> > substitute a 16K RAM for an 8K?
> >
> > Question, questionsà
> >
> > tom
> >
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Received on Sun May 13 18:29:55 2001