Switching them didn't work.. first thing I tried. I found this while googling:
"I purchased a pair of 3.1 ROM's which were in fact 27C400s. I also have the rev. 8.9 mobo which leaves pin 1 of the ROMs floating. I Never had a bit of trouble with them even when the mobo was over-clocked and ROM timing was set for the fastest speed. They had a mirror image burned into the upper and lower 256KB of each ROM so they would have worked with pin 1 to GND or VCC although left floating is usually resolved as a logical high by the internal address buffers.
I also have a pair of TC574200 which I burned a 512KB 3.9 ROM image into using the mirror method which worked fine with pin 1 floating also. It wasn't until I did the 1MB ROM hack that I finally got around to connecting pin 1 to A19! But that's just my personal experience. :razz:"
But then I found this:
"Still i did not have my KS3.1 at work and i also found out why: The Adresslines of A4000 and i guess also newer models of A3000 (Rev 8.x an higher) decode also A19 (from amiga) to A17 (on rom chip) which makes for a total of 1024K of rom space (18 adress lines, 16 data lines, 2 chips = 2^18x2(bytes)x2(chips)=1024Kbytes). On older Rev. (6.x, 7.x) A3000 A19 is not connected and that leaves room for max 512Kb. So since KS3.1 is (only) 512kb it should work great right? But my KS3.1 did not work. Looking a bit closer at my KS3.1 (they are eproms and not roms in my case) i found out that my chips are 4mbit (512kb) each so that totals to 1024K so that means only half of it it filled with the KS3.1 code and the other half is not used. Now how does the amiga select the 'right' part of the chip and not the part which is not used? It uses the extra adresline (Amiga A19, Rom A17) to do so! I think this extra line was intended for future kickstarts which might be bigger than 512K (Older KS1.2/1.3 was only 256K and grew to 512 starting with KS2.0). The A17(rom) line on the sockets on the ROM-Tower was not connected to A19 (amiga) but was connected to ground(0V) and with that it selected the unused part of my Eproms and that is why my KS3.1 did not work in my Amiga3000. Until now because after i reconnected the A17 lines from my eproms to +5V (which makes the amiga use the other half of my eproms) it finaly worked :-D :-D :-D"
I don't know what the chips are, but they are from Amiga on the Lake and are labeled as Amiga Forever 3.1 ROMs. Anyone know if 8.9 has a floating pin 1? I looked at the back side of the mb and there appears to be something coming off pin one of U181.. nothing on backside of U180 and was too obscured to see if something connected from the topside.
