From: Eric Ball/Markham/IBM <eball@xxxxxxxxxx
> Although it is possible that these are
> prototypes, I would suspect that a developer would more probably use a UV
> erasable EPROM rather than an OTP. OTP PROMs are considerably cheaper
than
> EPROMs, so these are probably pirate ROMs as has been suggested
previously.
> The only other thing they could be is an electrically erasable EEPROM, but
> I don't know when those first became available (and they are much more
> expensive than a standard UV EPROM).
I think the white ceramic gold-top package was pretty well out of
vogue by the time EEPROMs came along in the late 1980's. These
look very much 1982 tech. It was not uncommon in those days to
sell "E"-EProms in windowless cases as these were cheaper than
cases with windows, even though the chips were the same. (I have
some 8049's like this.) I would guess that these were made for
limited internal distribution -- play testing and the like -- where
recovering and erasing the chips would have been cost prohibitive,
yet the ability to program them in-house would have been necessary.
--Roger Williams
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