I managed to snag a second-hand Wyse Dx0Q thin client hoping to realize my long-standing dream of jury-rigging an eSATAp port and having an external 3.5" drive attached directly rather than over USB. The Dx0Q is especially good for this since it has onboard SATA as well as +5V and +12 headers available. Unfortunately, it was not meant to be. The unit I received wouldn't POST and the seller offered to replace it with HP t620. So be it.
Compared to t520, t620 has a larger footprint. Inside, however, not that much has changed.
- quad-core GX-415GA AMD APU
- two SODIMM slots instead of one
- two internal USB headers
- mSATA connector (not soldered - used in older revisions instead of the M.2 slot)
- PCIex4 connector (not soldered - used in the wider PLUS versions with a riser)
- the cooling solution is a bit bulkier
Externally you also get two PS/2 ports, audio line in/out and one 'customized' port - either VGA or serial. The rest is laregely unchanged from t520.
The upgrade was remarkaby straightforward. I moved the M.2 drive with my gentoo installation from t520, booted a live usb stick, chrooted into gentoo, updated efibootmgr and added
MAKEOPTS="-j4" to '/etc/portage/make.conf'. One thing I did not anticipate was that GX-212JC used in t520 is based on AMD Mullins gpu, while GC-415GA being one generation younger uses Kabini. That required updating the firmware loading facility in the kernel config.
And that is pretty much it. I should have some power consumption measurements next week.
The unit I received used one of the earlier BIOS revisions - version 2.08. Upgrading the BIOS was not obvious - the early versions didn't provide for 'tool-less' upgrades from within the BIOS or the UEFI shell. The hp linux firmware upgrade tool is also notoriously broken. I had to resort to a forced BIOS recovery using the Recovery USB flash drive (created with an HP tool provided in the firmware archive for Windows) with the procedure outlined here. It worked well.
Benchmarks and power consumption
I have run a kernel compile on both the t520 and t620 using the same .config. The only difference being make -j2 on one and make -j4 on the other. The wall clock was 55 minutes and 25 minutes, accordingly. More than double performance can be explained by the higher clock speed on the GX-415GA (1.5GHz vs 1.4GHz "boost" on GX-212JC).
In idle, both terminals sip about 6W running headless (connecting VGA adds about 1.5W). At full tilt the t520 pulls 10.5W while t620 maxes out at 14W. I think this is a reasonable price to pay for the extra performance.
By the way, I learned that my external USB 3.5" SATA enclosure pulls another 5W. Perhaps another reason to consider 'downsizing' to a 2.5" internal HDD...