D2114 versus MM2114N-2... or maybe more fakes? - Page 1
Forum section: electronics / projects

author: NivagSwerdna
author_rank: Super Contributor
timestamp: June 15, 2021, 01:27:25 pm
content: Some time ago I bought some 2114s off EBAY because one day I knew I would need one... so that day arrived and they don't work!Could these be fake?Is it a valid assumption that a MM2114N-2 would work in place of a D2114?Thanks in advance

author: newbrain
author_rank: Super Contributor
timestamp: June 15, 2021, 04:20:59 pm
content: Quote from: NivagSwerdna on June 15, 2021, 01:27:25 pmYes, and yes.The DSs I can find online tell me that the MM2114N-2 has a faster cycle time than the D2114 (200 ns vs. 400 ns), but this is usually not a bad thing - the other timings look compatible.As these are small, DIP packaged, and static memories, it should be easy to just put them in a breadboard and manually test some address, or create a more sophisticated test rig with an MCU.Nostalgic oldish man: I still remember when I expanded my self built 6502 board to a mind-blowing 4 kB, by stacking eight 2114s in two four chip high towers, all pins soldered in parallel but chip selects.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: June 15, 2021, 04:25:40 pm
content: Quote from: newbrain on June 15, 2021, 04:20:59 pmI did. That's how I suspect they might be fake.

author: james_s
author_rank: Super Contributor
timestamp: June 15, 2021, 04:45:37 pm
content: Do they do anything at all? They could be fake, or they could be defective. A lot of old arcade games used 2114 RAM and it seems to have a relatively high failure rate, it's one of the more common parts I've had to replace.

author: wraper
author_rank: Unknown
timestamp: June 15, 2021, 05:06:34 pm
content: I don't think that laser marking is possible on genuine component this old.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: June 15, 2021, 05:13:14 pm
content: Quote from: james_s on June 15, 2021, 04:45:37 pmI seem to see 1s even if I wrote 0's. Was just checking my sanity.

author: james_s
author_rank: Super Contributor
timestamp: June 15, 2021, 06:17:55 pm
content: Probably fake then if they always output 1s. IIRC the ones I've had fail usually had a single stuck output.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: June 15, 2021, 06:39:46 pm
content: As per usual I have a small collection of these... and I notice... some have notches, some don't, some have big indents near pin 1, some don't.Sigh

author: newbrain
author_rank: Super Contributor
timestamp: June 15, 2021, 06:54:25 pm
content: If "JM47AS" is a date code (quite probable), it seems extremely fishy to have so many different packages...The genuine ones tend to get really hot even at idle (IIRC idle current is in the 100 mA range), how do these behave?

author: sarahMCML
author_rank: Regular Contributor
timestamp: June 17, 2021, 01:48:03 am
content: If you still need one or two I have about 10 NOS that I bought way back in the late '70s when I built my 6800 system. I'd be happy to put a few in the post if you wish?Regards, Sarah.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: June 17, 2021, 08:20:29 am
content: Quote from: sarahMCML on June 17, 2021, 01:48:03 amThat's very kind. Real 2114 are just about still available so I ordered a couple from cricklewood electronics whom I have found to stock real things in the past at least.