Looking into N64 RDRAM

For no probably real useful reasons I've been working on an N64 emulator that I started a couple years ago and recently sort of picked back up. It's not that far along and maybe never will be. But while digging into information about the N64 something that's bothered me is the lack of measured real timing data from the system.

Particularly for it's complex and lumbering RDRAM controller that has to serve a bunch of different sources (CPU, RSP, RDP, VI, PI, SI, refresh, etc), some I imagine must be higher priority than others.

With the advent of FPGA N64 reproductions including commercially available ones like Analogue64 I kind of suspect there's been some work done somewhere, but I haven't seen it. So I was wondering, how hard would it be to try it myself?

I've done a little bit of hardware testing/reverse engineering before, but not hardware inspection. So while I've done a decent amount of looking at electrical signals in oscilloscopes for other things this is probably going to be a big learning (or failing) experience for me. And it might get a little expensive. But it's the holidays so I've decided to do some spending on this.

So what am I after and what hardware will I need? For right now at least I just want to capture some RDRAM bus data.

The nice thing about the RDRAM interface is that it's pretty narrow, just 9 bits of data and a few clock and control signals, and it happens to be exposed via an external port with a commercially available memory expansion pack so I can probably pretty easily physically access it without having to open a console.

The not so nice thing about it is it's fast: 250MHz double data rate, probably requiring at least 2GHz sampling to reliably capture. That's beyond the capability of any cheap and easy to obtain USB logic analyzer I could find, so I had to look at something fancier. This is what I settled on:

Keysight 16821A 34-channel Logic Analyzer 

It's obsolete and I bought it used off eBay for about $700. The new models are far too expensive to consider (upwards of $40,000!) so I'm hoping this will suffice.

For software testing on the N64 I ordered this:

Kaico SummerCart64 Open Source N64 Flashcart

Of course I will need an actual N64, which I've never owned. And I'll need at least one controller and the memory expansion pak. These items I can probably pick up locally somewhere while I'm waiting for the other things to ship.

Finally I'd like a way to conveniently view the output of the N64 without needing a separate TV or monitor. My inclination was to use a USB capture device that supports N64's composite or S-Video video output. But these are kind of hard to obtain and since I'm using a Linux desktop I'm concerned about driver support. So instead I'm going to be looking at using my monitor's Picture in Picture mode with HDMI - meaning I need to convert the N64's output to HDMI with this:

RetroTINK-2X MINI

So that should be it for the easy part, getting the necessary hardware. Hopefully I'll be able to get to the less easy part of showing actual data in a later update.