Replacing a bank of 4116 RAM with a SRAM replacement?

NivagSwerdna

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I really don't want to re-invent the wheel if possible...

I have a board (actually Tutankham) which has multiple 4116 failure... I think something traumatic must have happened to some of the power rails in its past.

I am thinking of replacing the eight 4116s in a row with a static ram and some latches but obviously there is a certain amount of complexity with the timings.

Has this been done before? Is it open source?

Thanks in advance
 
There's a few links out there doing similar stuff, particularly modding the Sinclair Spectrum to use SRAM (example here http://sindik.at/data/vram/), quite easy as Din and Dout are tied together.

I looked at doing similar ages ago for Williams hardware but as that uses separate Din and Dout for the RAM I didn't progress very far
 
I've done it on redesigned boards, but it doesn't really make sense to make a module to do it on existing boards.

On a redesign, you just eliminate the final CAS/RAS muxing to give a full set of address lines. For a plugin, you need to latch half the address on the falling edge of RAS, and the other half on the falling edge of CAS, then generate ~CE, ~OE, ~WE from the other signal (taking into account how DRAM refresh is handled on the design to make sure you ignore those cycles), then make a board that plugs into ALL of the RAM sockets since you need DI, DO from each chip, and add a buffer and logic to isolate DI from the RAM data bus.

Just replace the 4116s with 4164s. You're going to need to remove and socket all of the DRAMs to do a plug-in anyway.
 
I also found...


That seems like it might work.

I do accept the points above... It might not be worth the effort.

I don't actually have any 4164s... Might look to see how available those are near me. Are the pin compatible apart from the obvious 12V and -5V?

The difference is that goes on as a plug-in for the TMS where all the pins you need are easily accessible rather then plugging into the RAM sockets.

(And for the TMS, it's easier to just use 4164s to replace the 4116s)
 
I was able to use an ISSI SRAM to replace 6x 2114 and ECL RAM on a Donkey Kong and DKJr board.


I tried to do the same with the 82S09 buy have not yet figured it out.

It seems like this one could be done. Only you get to decide if it's worth the effort.
 
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