For the A500, A1200: Comparing the pinouts of the
MX23C2100 and the
27C400 from their datasheets. Pin 1 is the only difference between the two. MX23C2100 has this as a no-connection pin and the 27C400 has this pin as Address input A17. This must be what jope is talking about here:
Quote:
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Originally Posted by Jope
Just burn it another time to the top of the chip if unsure. Otherwise tie the highest address line to ground with a jumper wire.
The chip won't magically overwrite your slow ram, as the machine will only address 512kB or ROM.. If the surplus address line is left hanging, there's no telling what the chip will give out at any given time (thus burn the image two times to fill the high half of the chip if you don't plan on making sure that the address line doesn't float).
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However, for the A600 and A500+, the 27C400 is identical pin-for-pin to the
MX23C4100