@lawrie Thanks for the tip! In the mean time it runs a much enhanced version of V6 with elements taken from V7, V8 and V9 and the TCP/IP stack from BBN (that ended up in 4.2BSD). This is what I want to get running on the ULX3S. It will also be the machine that talks to the Blit, running on another ULX3S.
For a while in 2017/2018 I was planning to do a similar SBC with a 99105 or 99110 CPU and a better MMU. But then @Speccery convinced me that FPGA's were perhaps a more interesting route to go. It took me a long time to overcome my reluctance to a multi-gigabyte vendor tool download, but took the plunge. Luckily Trellis was just around the corner, as was the ULX3S.
@e2kgh Yes, that is the blit I am talking about. There is a nice video here: http://doc.cat-v.org/bell_labs/blit/ For some background discussion see this Blit thread on the Unix Heritage mailing list https://minnie.tuhs.org/pipermail/tuhs/2019-December/date.html
The Blit has (intentionally!) very simple hardware: just a basic 68K system with a bitmapped b/w graphics display. I have that done. All it needs now is a keyboard & mouse interface. I have two plans for this (i) use Goran's pmod and add a PS/2 mouse and keyboard - this requires some changes in the Blit software, but that is not a hard thing to do (it is standard 1980's C source code and a little bit of 68K assembler); and/or (ii) build MicroPython 1.12 (with IP forwarding enabled) and experiment with a bluetooth mouse and keyboard - this too requires some software changes for the Blit.
Although it is more work, I like option (ii) as it has far less wire clutter on my workbench.
1-bit mode SDCard(slot=3): >>> import sdtest ['long_file.bin'] 1056 KB in 752 ms => 1404 KB/s file read 4096 KB in 2746 ms => 1491 KB/s raw sector read 4-bit mode SDCard(): >>> import sdtest ['long_file.bin'] 1056 KB in 492 ms => 2146 KB/s file read 4096 KB in 1777 ms => 2305 KB/s raw sector read
It is not difficult to be faster than a 1980 MFM hard drive. For example the ST506, which is similar to the disks on the mini-computers of the late 70's. The track-to-track seek time was ~5ms (3ms step + 15ms settle) and there were a lot of track seeks happening. The main s/w optimisation was to sort the pending disk accesses by track, to minimise the seeking. The data rate was 5Mb/s = 625KB/s. The SD Card will not be the bottleneck, and even with the SPI_IDE bridge it will be about the same.
Many thanks for the testing & measuring - much, much appreciated!