Notes about Intel's chip markings.
Older ceramic DIP chips may have no prefix, due to the fact that there were no other chip packages to have to distinguish them from.
Also some preproduction chips bear no prefix.
Intel's PDIP styles. Chip marking styles.
Early plastic DIP chips bore different notch and marking styles from the later standard Intel adopted.
This may not apply to CPU's but does to MCU's. Support chips marking shown as example.
 16 pin DIP long square notch print, no etching |
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 28 pin DIP long square notch smooth surface large print, no etching |
 40 pin DIP long square notch smooth surface small print, no etching |
 28 pin DIP round notch smooth surface medium print, etched |
 40 pin DIP round notch textured surface smooth rectangle impression etching & print AMD clone shown but same style as Intel |