[jan-jaap]

Another graphic, for funzies:

Here's one for the R2300 MBC:

   

They announced 3 speed grades: R2100 (5MHz), R2300 (8MHz) and R2600 (12.5MHz). R2600 was released later when SGI already had the IP4.

This was before the R2010 FPU chip was ready, but the FPU socket specification had been defined. So they designed an FPA (floating point adapter): a daughter card for the R2300 that used the FPU socket. The FPA used a Weitek chip. This was significantly slower than the R2010 FPU but I guess it was worth it to get a product to market.

You can see that the R2350 memory boards use a private data bus to communicate with the CPU. This is probably implemented with the user-defined pins on the VME bus.

MIPS sold the M/500 development system with the R2300 CPU board set, also in a 12-slot VME chassis with an ESDI disk. Likely used the same Interphase V/ESDI-3201 controller.