The basic idea is that Remem implements in CPLD a memory management unit dividing the 64K address space into 64 1K blocks (actually more than that since the option ROM is emulated). So you can map any 1K block from anywhere in RAM or flash into the 64K address space any way you like. For compatibility it also emulates a 256K "Rampac" which is a vintage external device that hooks to the I/O bus port on a T102. There are multiple MMU maps selectable via an I/O instruction for fast-switching of virtual Model 100 environments. So for example you can have one map with a native Forth-in-ROM, and a couple of maps with the standard ROM but distinct RAM portions (the latter much like the "banks" in a T200 or NEC 8300 laptop) Each block in the map can be marked read-only so that if you are emulating ROM with RAM or flash you get a perfect emulation, i.e. any writes against ROM don't get applied. Also remem allows running any option ROM by loading the image to flash or RAM and mapping it into the option ROM bank. -- John.