quicknick wrote on 2022-08-15, 18:42:

Was that even a thing, chips coming from the manufacturer already programmed?

I know this as Mask ROMs...
https://handwiki.org/wiki/Mask_ROM

quicknick wrote on 2022-08-15, 18:42:

Earlier this month I received 5 pieces of AT27C512R (from a seller in Europe) for experimenting with an alternative Imagine128-I […]
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Earlier this month I received 5 pieces of AT27C512R (from a seller in Europe) for experimenting with an alternative Imagine128-II bios (more details here).
To my surprise, all of them were already programmed with some sort of code. I explained this to the seller, and he agreed to send me another 5 pieces if I provide a photo proof that I destroyed the chips.
Few days ago the second batch arrived, but I was away so I could test them only today. Despite being a somewhat different specification (AT27C512R-12JI instead of -12JC) and being properly sealed in their tape/reel packaging, they are all programmed with the same data, identical to the first batch!
Was that even a thing, chips coming from the manufacturer already programmed?

Here's a dump, if anyone is curious and could maybe identify the equipment for which these were made:
(the only plain text inside is "20030Utility Meter" at around 4EAA)
at27c512r.rar

You can get this as a service from companies like Digikey, it could be they're reselling some old reels that a company had pre-programmed before they were shipped by the supplier.
Example: https://forum.digikey.com/t/custom-programming/693

But Mask-ROMs were not writable while EPROMs are.
Back in the days companies used to distribute new BIOS versions (a rare incidence) or other DATA via preprogrammed EPROMs through their regional subsidaries (not everybody owned an EPROMMER, there was almost no Internet to distribute files).
So EPROMS got programmed and then distributed.

I wouldn´t consider this an issue when buying chips today - they only were protgrammed once after all.

Don't bother with OTPs, better look for pin compatible EEPROMs, such as Winbond W27E512 or SST 27SF512.

furan wrote on 2022-08-15, 19:11:

...it could be they're reselling some old reels that a company had pre-programmed before they were shipped by the supplier.

I think that explains it, most likely.

SSTV2 wrote on 2022-08-15, 19:21:

Don't bother with OTPs, better look for pin compatible EEPROMs, such as Winbond W27E512 or SST 27SF512.

I ordered some W27C512P but they come from China and I'm still waiting for them.

quicknick wrote on 2022-08-15, 19:34:

SSTV2 wrote on 2022-08-15, 19:21:

Don't bother with OTPs, better look for pin compatible EEPROMs, such as Winbond W27E512 or SST 27SF512.

I ordered some W27C512P but they come from China and I'm still waiting for them.

Mind the difference: W27C512P is an ERPOM, hopefully not OTP. SSTV2 recommended W27E512, which is an early EEPROM (a precursor of flash chips). This is WRONG! The W27C512 seems to be a later variant of the W27E512 (at least looking at the revision history in the data sheet). Both of them are EEPROM!

I had no issues reusing flash bio chips from old junk boards as EPROMs. I did this with hot swap on a motherboard to flash in two pieces of firmware and installed on a cache spock scsi controller.

Cheers,

pentiumspeed wrote on 2022-08-15, 21:20:

I had no issues reusing flash bio chips from old junk boards as EPROMs. I did this with hot swap on a motherboard to flash in two pieces of firmware and installed on a cache spock scsi controller.

BTW: buying silicon ICs; be cautious about pieces from Chinese sellers, they were substandard.

Cheers,

Seems to be a EEPROM, though:

The W27C512 is a high speed, low power Electrically Erasable and Programmable Read Only
Memory organized as 65536 ´ 8 bits that operates on a single 5 volt power supply. The W27C512
provides an electrical chip erase function.

quicknick wrote on 2022-08-15, 21:37:

Seems to be a EEPROM, though:

You are definitely right. Sorry for the misinformation.

Heh, no problem! I'm glad I didn't order the wrong part. I sometimes do that 😁