Thanks!
With both BIN files you can write whichever version you want (two-way comms or the BM-as-link-room-mode only in 1.6, as you pointed out in Discord).
The chip in my unit (and the replacement) was a generic 27512 EPROM, which is still readily available. Mine was M27512FI, ie. by STMicroelectronics but any manufactorer should be fine (as long it’s the same 28-pin DIP package). I couldn’t find the speed rating for either chips, but in this case I’d guess the “slowest” 200ns part should work (elsewhere, like vintage computers the speed of the ROM might be important). You’ll also need an UV-eraser (for the old EPROMs with window on top) and an EPROM programmer. I’m sure there are also newer pin-compatible variants (EEPROMs, ie. no UV-erasing needed, or write-once chips if you just want to write a chip once and not re-use it).
I find it interesting that the BM4500 was shipped with the “limiting” software (if the 2-way IR hardware was fitted). Also the release notes telling a fix for “Beosystem 4500 may intermittently block and it is necessary to remove the mains plug” sounds pretty annoying bug, and surely would’ve caused calls to dealers! (I might have actually experienced this on my unit with the old ROM once or twice, I always thought it was just an effect of a low battery but apparently not!)
