You can replace EPROM with EEPROM so long as the pinouts are compatible. One thing to keep in mind though. Parallel EEPROMs in the 28C part numbers are not readily available in sizes as large as EPROM. The largest 28C parallel EEPROM I could find is 128Kx8. The EPROM in your example is 512Kx8 so you won't be able to replace that specific EPROM with 28C part number EEPROM. Not as an easy drop-in, anyway.

Parallel flash memory could work though.

Flash EEPROM should work and is available in that size and larger. 29F040 should work.

I spoke too soon.

ebay.com link: 1PC XICOR X28C040M 20 MIL SPEC 512K x 8 200NS 5V CMOS EEPROM MODULE

A little pricey though

What I've been doing - when I don't have stock of EPROMS are just using the .. uhm... non-erasable ones. (PROMs?) Program once, and leave it.

Sorry, EPROM - Erasable. EEPROM - Electrically Eraseable.

There are PROMS out there - write once. Can't erase at all. That's what I'm meaning. They're rather cheap, like, in the $1 range.

I don't worry about getting EE or E PROMS anymore. I burn them once, that's it.

That'd drive me nuts

Didn't see any one mention that some EEPROMs are rated much shorter data retention life than regular EPROMs. Like 10yrs or so after written to. Atmel 28C series is like that. Then again, who knows what is spec'd versus how long it may actually work. There's probably other options available with longer retention though.

https://pinside.com/pinball/forum/topic/28c16-eeprom-replacement-for-2716-eprom#post-1013785

That was something someone mentioned, I think on RGP, when I inquired about my discovery of EEPROM replacements for 2716s.

I would guess a game would stop booting or start acting wonky if the data was degraded? I wonder what the specific symptoms would be. 10 years is a while, though it would suck for a game to have changed a few hands and not be able to track the problem down to degraded roms. Would it just be a matter of erasing and writing them again to reset the 10 year clock?

I keep all my programmed ROMs in a small drawer. I still have ones programmed for TZ 9.4H beta from years ago. Every once I'll pop one in to test something. For me, it's easier than waiting for one to erase, then pull out programmer and program it up..

I'd be really curious if any pin game has used the SAME ROM so long that it's reached it's EOL. Be interesting to see what happens. (Checksum error?)

Yes, I believe that's how it works. It's not that the eeprom cannot be reused, but has to do with whatever technology stores the bits. So when it stops working, erase and good for another 10+ years. Data Degradation .. https://en.wikipedia.org/wiki/Data_degradation

Yeah.. if/when it does fail it'd mean some bits changed -- so wouldn't pass any checksum routines. I think this happens fairly often in pins actually.. when you get a board and one of the ROMs is bad.. or maybe it verifies good a few times, then bad.. then good a few more times.

I took a closer look at the 29F040 data sheet and the pinout is NOT compatible with 27C4001.

What will happen when the ROM degrades will really depend on the game software and which bits fail. Best case scenario would be that it doesn't boot and gives a ROM error. A lot of games will probably fall into that category. I've seen games fail with bad ROMs and still boot but act weird so that's another possibility.

EPROMs are still the best option for me personally. Erasers are available in the ~$15 range and I do a lot of ROM burning so it makes sense for me. For someone doing one-off ROM burning I could see the EEPROM option working out cheaper, but you still have to buy a programmer and the ROMs are most likely going to be more expensive so you don't have to burn many before the EEPROM solution starts to be more expensive. PROMs could possibly be a good option if you are able to get them cheap enough.

I realize it's not all about price, but the only real gain with EEPROM is convenience and it's not that much more convenient (IMO) given the cost and possibility of reduced date retention life vs. EPROM.