2116 and other old memory chips

From: Richard Erlacher <edick_at_idcomm.com>
Date: Sat Jul 7 10:48:02 2001

I have to disagree ... i2115's are open-drain versions of the tri-state i2125,
and both of these are single-supply 1k x 1 SRAMs. If you plug a 2115 into a
2116/2117 application, you'll quickly become aware of the differences since the
single-supply 2115's Vcc will be at gnd, and its gnd will be at +12, its nCS
will be at -5, and the A5 input will be connected to +5. I would expect the
package to pop within less than 10 seconds. I did verify this information from
the 1987 Intel Memory Components Handbook. 16K DRAMs were no longer of
interest, and, since Intel actually never manufactured them anyway, simply
packaging someone else's parts with their brand label, there was no need for
them to include the 3-rail 4116-equivalents in their databook.

Intel did take a stab at selling (I don't know whether they attempted to build
them themselves.) Single rail 16-K DRAMs, the 2118's, which were also touted as
the fastest DRAMs on the market at that time. With the rapidly approaching
availability of the 4164's, this was a stepping stone to the larger memory
arrays that were of great appeal to the users of the new 16-bit CPU's, allowing
board makers to design boards with single supplies. However, the Intel DRAM
controllers of the 16K era, i.e. the i3242/i3480 combination, didn't deal with
mulitiplexing 16 bits of address, so would-be designers of 64K DRAM-compatible
memory boards had either to wait for the new generation of DRAM controllers, or
to design their own multiplexing/refresh-address-generation logic from TTL
SSI/MSI, or perhaps PALs.

Dick
----- Original Message -----
From: "Bob Shannon" <bshannon_at_tiac.net>
To: <classiccmp_at_classiccmp.org>
Sent: Saturday, July 07, 2001 8:48 AM
Subject: Re: 2116 and other old memory chips


> 2115 drams are 3 rail.
>
> 2114 srams are 5 volts only.
>
> 2104 drams are also 3 rail.
>
> Louis Schulman wrote:
>
> > I am in the process of attempting to repair, with Pete Turnbull's
> > invaluable guidance, an Exidy Sorcerer.
> >
> > The manual recites that the memory chips, depending on configuration,
> > are 2104 (4k) or 2116 (16k).
> >
> > A casual perusal of chip sources shows that most begin their dynamic
> > ram sections with 4116 chips. The only mention I have found of 2116
> > chips is in a reference to the original IMSAI memory board.
> >
> > So, my questions are: Are 2116 chips 3-rail? Are 4116 chips
> > equivalent? Does anyone have a source for 2116 chips, if they are not
> > equivalent? What about 2114 static ram (used in the video section of
> > the Exidy)? Same problems? Were they all three rail?
> >
> > A general lecture on the nature of old memory chips and their use and
> > selection would be very helpful (hint to Tony Duell).
> >
> > Thanks, Louis
>
>
Received on Sat Jul 07 2001 - 10:48:02 BST