Just because the Classic, LC, and IIsi were released together doesn't mean they share any architectural similarities.
The IIsi uses the MDU memory controller found in the Iici.
The Classic uses the BBU memory controller (well, calling it a memory controller is a stretch, it acks some bus accesses and moves physical ram around so the machine can boot out of ROM) found in the SE.
The LC was the first with the new memory controller also used in the LCII.
The physical locations of hardware are also their logical locations in machines without an MMU. Hardware lives at physical addresses, those don't change. An MMU, the processor can present a logical view that differs from the Physical view. Without an MMU, the two are necessarily the same. The memory controller in all macs going back to the 128k do some amount of moving the address space around, for example although ROM physically lives at 0x400000, the memory controller makes it available at 0x0 on boot so the processor can boot from it, then moves the bottom of RAM to address 0x0. The II and the LC memory controllers do a little bit more to allow the 24bit/32bit views of the world.
The Classic has SCSI at 0x580000, SCC registers at 0x900000, IWM and VIA above that. They don't live at the same locations as on a Portable.
The LC, supporting 32bit accesses, has things arranged more along the lines of the Mac II and subsequent 32bit capable machines. The hardware lives in the 0xF00000 range in 24bit mode.
The IIsi uses the MDU memory controller found in the Iici.
The Classic uses the BBU memory controller (well, calling it a memory controller is a stretch, it acks some bus accesses and moves physical ram around so the machine can boot out of ROM) found in the SE.
The LC was the first with the new memory controller also used in the LCII.
The physical locations of hardware are also their logical locations in machines without an MMU. Hardware lives at physical addresses, those don't change. An MMU, the processor can present a logical view that differs from the Physical view. Without an MMU, the two are necessarily the same. The memory controller in all macs going back to the 128k do some amount of moving the address space around, for example although ROM physically lives at 0x400000, the memory controller makes it available at 0x0 on boot so the processor can boot from it, then moves the bottom of RAM to address 0x0. The II and the LC memory controllers do a little bit more to allow the 24bit/32bit views of the world.
The Classic has SCSI at 0x580000, SCC registers at 0x900000, IWM and VIA above that. They don't live at the same locations as on a Portable.
The LC, supporting 32bit accesses, has things arranged more along the lines of the Mac II and subsequent 32bit capable machines. The hardware lives in the 0xF00000 range in 24bit mode.