[vcf-midatlantic] Good source for eproms?

David Riley fraveydank at gmail.com
Thu May 26 14:29:01 EDT 2016

On May 26, 2016, at 1:56 PM, Jonathan Gevaryahu via vcf-midatlantic <vcf-midatlantic at lists.vintagecomputerfederation.org> wrote:
> On 5/26/2016 1:41 PM, David Riley via vcf-midatlantic wrote:
>>> On May 26, 2016, at 00:48, Dave McGuire via vcf-midatlantic <vcf-midatlantic at lists.vintagecomputerfederation.org> wrote:
>>>  Yup, "OTP" EPROMs.
>> I think that's just called a "PROM". :-)
>> - Dave
> No, from what I understand of the usual usage of terms, PROMS are the bipolar/fusible link parts like 82s137, MMI6301, etc. These can be open collector or tri-state.

Well, a PROM is a ROM that can be Pd, but not Ed. :-)  The underlying technology doesn't matter, though the interpretation of the term may be a little loaded with assumed meaning.

> OTPROMs aka OTP EPROMs are floating gate 2764/27128/etc EPROMs with no window, so they can't be erased with UV light (though, as we can see here, age can still cause them to become slowly erased).

Ah, that makes a little more sense.  I hadn't thought about the X-ray erasure mode of operation.  It's not really OTP then, though.

> Mask ROMs are the 2364/23128/etc parts which are mask programmed at the chip fab, and never lose their contents unless they lose their smoke.

Or unless electromigration takes out a path or two, but that's a much longer process and akin to losing the magic smoke.

- Dave

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