I've finished the schematic for the two boards and once the parts that I have on order arrive, I will begin making wire-wrapped prototypes prior to sending the boards off to be fabricated. Overall, the design is a lot more flexible and a lot less complicated that I thought it would be.
The VME board itself will be somewhat expensive due to the physical size of the board. For this reason, I want to make the board as flexible as possible to allow for future changes without having to spin off a new board. While rhombus is a 68020 board, I do plan on moving up to a 68040 for my next project, and I'd prefer having a VME interface that will accept the new CPU board with no physical changes. The board itself is rather simple... a CPLD, an EPROM for doing the address modifier lookups, and the bus buffer/transceivers.
With regard to rhombus, the board is actually going to end up being smaller than my current wire-wrapped prototype, mainly due to switching to the PLCC-packaged MC68901 and ROM. RAM is going to be tested with DIP parts, however it will be replaced with 4x 44-TSOP packaged ICs once I run off copies of the board. There will be a need for pull-up resistors as some of the CPLD outputs are needing to be changed to open collector as they will also be potentially driven from the VME bus header.
I also plan on adding a flash configuration rom and creating a basic configuration utility, but i'm currently debating a few design choices. Primarily the flash rom will be useful for storing information about add-in cards on the VME bus, and thus generating the necessary address modifier codes. Additionally, it will store things found in traditional PC BIOS, such as date/time, serial port configuration, etc. As such, there is potential need for the ROM to exist on the stand-alone CPU board as well as on the VME adapter board. I'm thinking of going with the latter, and allowing the CPU board to read data from the flash ROM if it is present and reverting to either jumpered values or values programmed into the CPU-board's EPROM if the flash device is not present.