I obtained these wafers from the old Dallas Semiconductor Research Center many years ago. I assume them to be experimental prototypes or early runs of these products. It\'s certainly not the norm for more than one type product to be on a single wafer, but I have seen it before.

In any case, they are beautiful specimens of one of the most famous and abundant CPUs in history.

Here is some information about the chips themselves.

The DS87C520 andDS87F520 FLASH memory version both on one wafermanufactured by Dallas Semiconductor in 1997.

The DS87C520/DS83C520 EPROM/ROM high-speed microcontrollers were fast 8051-compatible microcontrollers. They featured a redesigned processor core without wasted clock and memory cycles.

As a result, the devices execute every 8051 instruction between 1.5 and 3 times faster than the original for the same crystal speed. Typical applications will see a speed improvement of 2.5 times using the same code and the same crystal.

The DS87C520/DS83C520 offered a maximum crystal speed of 33MHz, resulting in apparent execution speeds of 82.5MHz (approximately 2.5X). The DS87C520/DS83C520 were also pin compatible with all three packages of the standard 8051, and included standard resources such as three timer/counters, serial port, and four 8-bit I/O ports.

They feature 16kB of EPROM or mask ROM with an extra 1kB of data RAM. Both OTP and windowed packageswere available.
The fully processed wafer will change colors depending on viewing angle and lighting conditions.

Photos were taken under ordinary incandescent room light. Photomicrographs were made using halogen lights. I\'ve got a wide selection of other wafers in my store.Thanks for looking!