Writing a new SDRAM controller – part 3 – 2021-07-25

In the previous instalments I talked about improving throughput by interleaving read and write transactions to different banks, as well as access patterns I need to avoid and some subtle timing issues which need to be considered.

The challenges remaining to be solved are ensuring that the controller responds in good time to incoming requests on multiple ports, and making the controller run fast enough that it meets timing at the desired speed. For the PC Engine core the desired clock speed is 128MHz

Writing a new SDRAM controller – Part 2 – 2021-07-10

Last time I talked about the form of a typical SDRAM read cycle, and how we can improve the overall throughput by interleaving reads to different banks.

The same principle applies to write cycles, too.

Part 1 – 2021-07-04

In my last post I talked about the need to adjust the SDRAM controller used by the Megadrive core to make it work on the TC64V2, and having released that port it was time to turn my attention to the PC Engine core.

This one has actually been on the back burner for months. I started to port it at the beginning of the year, found that it didn’t work on TC64V2 and didn’t yet understand why not. With plenty of other projects to keep me busy I neglected this one for a while, but revisited it recently, armed with fresh knowledge about why it wasn’t working.