A trip down memory lane   Leave a comment

We re-discovered a stash of EPROMS and as a result, have stumbled upon a fascinating historical cache- the (literally) visible evidence of rapid technological advancement. The oldest chips are an old Intel set from 1973, and several models from the late 1970s through late 1980s. Here are three images of the Intel 1602A taken with oblique reflected light illumination:
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This chip has 2k of storage, arranged in 2 x 1k arrays. It’s possible to clearly see each individual component of the field-effect transistor which comprises a single bit of storage. A much different perspective is provided by switching to epi-illumination:

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which allows clear identification of the source, drain, and gates.

14 years later, in 1987, Fujitsu manufactured an 64k EPROM, the MBM27C64:

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These images were taken at the same magnifications as the first three images of the Intel 1602A, using the Luminar zoon, 100mm luminar, and 40mm epi-luminar. The feature sizes have significantly shrunk, but there is a clear structural relationship between the two devices.

We have about a dozen memory chips ranging from these early EPROMS through a recent 1G flash RAM, and will post them as they are available. For now, here’s an image of the 1G flash RAM taken under the same magnification and lighting conditions as the first 1602A image:

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We look forward to filling in the evolutionary tree….

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