Re: Gottlieb RAM question

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 08:41:35 2001