I've put together a new revision of the Mackerel-10 PCB to fix the issues in v1.0. The main problems with v1.0 were in the IDE interface. I had the direction of the buffers reversed which required a cut trace and a bodge to fix. I also failed to connect the second IDE chip-select pin to the CPLD, so that had to be bodged in as well to enable control of the IDE interrupts. With the circuit corrected, the IDE interface is working as expected without any bodges.

There are actually two very similar versions of the revised PCB. Originally I created v1.1 which fixes the issues listed above. After experimenting with the DS1233 reset circuit on Mackerel-30, I decided to add it to Mackerel-10 as well, replacing the 555 circuit that was doing the job previously. This version is v1.2 and is identical to v1.1 other than the reset circuit. If you would like to build one of these boards, I'd recommend v1.2, but v1.1 is still an option if you'd prefer to use the 555 reset.

As discussed in a previous post, the DRAM controller is running at 50 MHz with good stability. It is also decoupled from the CPU clock. My 68010s start to have issues with even a slight overclock, but the system runs well with the CPU clock at the rated maximum of 10 MHz. Using the 68SEC000, I'm able to run at 20 MHz. The SEC chip is capable of much more, but the DUART and IDE interfaces start to behave erratically beyond that point. It's possible that some additional wait-state logic would remove this bottleneck.

Finally, I've made some progress on the software side as well. The bootloader now supports the FAT16 filesystem and can load the Linux image from a file on the IDE drive instead of reading raw sectors into memory. I've set up the SD card with a small FAT16 partition containing the kernel image file and a larger ext2 partition. The ext2 partition can be mounted from uClinux and gives Mackerel-10 an option for writable persistent storage.

At this point, I don't have any immediate plans for more hardware changes to Mackerel-10. The current PCB satisfies all of the requirements I had for this system when I started. My focus has shifted to Mackerel-30, but there are still some interesting software options to explore on Mackerel-10.

Mackerel-10 Release Files: https://github.com/crmaykish/mackerel-68k/tree/master/releases/mackerel-10