SRAM cache looks like a possibility.

I am still looking at the system issues, but it looks like it is possible to get an external cache on the NeXT in the same way that the Nitro did. There are a few things that I am still looking into, such as if I can do some bus overclocking (relative to the NeXT bus). I found a document called the "MC68040 Designer's Handbook" that has an example cache scheme. Mine is a little different; however, it's good to know that my notes aligned with what Motorola did.

Handbook is in as of SVN rev 37.

exploding scope...

As most projects do, they explode in scope once you start thinking more about them. Once I decided that I could have a unified 040/060 socket, I then realized that I could add a cache. The issue is keeping the cost down; however, having 4 megs of cache on a system with 16-megs of memory would be a significant speedup. I will need to look at the cache flushing policies for NeXTStep.

unified socket.

I've been working so that I can reuse the 68060 board with 68040s. It will require soldering some resistors, but I believe that I can get it to work. I need to make the 68040 not be multiplexed because I want to keep the level shifters that will just shift 5V to 5V.

The two issues that I need to resolve is how to handle BCLK and /CDIS. I need to keep /CDIS high during reset so that it does not multiplex the bus. I will just use external logic to multiplex. I guess that I can just have a BCLK line waving around and making noise, but I would rather not. After I handle /CDIS, I will finish the clock circuit.

unified footprint for 040/060

I happen to have 40MHz 68040. I realized that with a few changes to the clock circuit, and adding a bypass, I can make my adapter also take a 68040 with the PCLK line at a higher speed. I will be modifying the schematics to reflect this change. It basically costs nothing as far as space.

I broke KiCad, and it won't compile

I didn't actually break KiCad, but my old Mac died that had it. The PC that I was using that had it just also died. All of this happened in time for my new mac to arrive, Japanese keyboard and all. （マクの日本語の入力がすごく好き）

I've been trying to get KiCad to compile, to no avail. I will have to put this off until I'm in a place where I get better 20k/sec in a few weeks. I have a windows xp disk around here somewhere, so I might just put it in vitualbox if I can find the install media.

Sockets started!

I've started on the foot prints for the ICs. You really don't realize how many pins 179 is until you go and actually make a socket.