If you compare this graph with the previous one in this post, there’s a few things you should notice:
- First, the overall boot is happening about 1 minute quicker, with a fully loaded chassis coming in around 2:35. This does mean the graphs are not directly comparable, because while the events covered are essentially the same, the total time shown is less. This graph is 1:36, vs 2:15 on the older one.
- The green and gray spikes are considerably spikier, basically more narrow. This means that the accesses are short and fast, exactly what we want. Notice that the graph is now 2 seconds between data points instead of three.
- A full 1:00 of the 1:36 shown is CPU bound. This is what we want — get our disk access out of the way so the CPU can go as fast as it can. More blue at the top of the graph is ideal.
- I do feel that further optimization of the disk subsystem is possible. I’m not seeing read/write data rates beyond 4MB/s, which is sad. I really wanted 8MB/s and beyond. I have more testing to do to see if it’s the 16700A or the SCSI2SD. The SD card is not the bottleneck, proved through testing.
- There is this 9-second delay near the beginning of the boot. I think that might be DHCP request/reply time. I could go static and eliminate that. Interesting that both the disk and CPU are just sitting there twiddling their thumbs.
With super helpful conversations with Glen Slick and others on the HP-Agilent-Keysight-Equipment groups IO group, and also a shit load of personal research, we’ve figured a few things out:
- LASI, one of the custom HP ASIC(labeled 1FT1-0002 on mainboard) used in the 16700X, does have NCR53C710 implemented as a softcore.
- NCR53C710 does support 10MB/s operation.
- The NCR53C710 megacell, as HP refers to it, as implemented does not have full support for 10MB/s, and is limited to 5MB/s maximum. This is per LASI Engineering Requirements specification.
- Optimization beyond 5MB/s using LASI as the SCSI Host controller is probably not possible.
I don’t usually give up this easily, however, and have some plans to bring faster storage I/O to the 16700. I’m not sure exactly what this looks like yet, but stay tuned!