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CompuLab Fit-PC3
Selecting the Machine (Iris)

Jim Carter, 2014-02-13


Aurora is our Dell Inspiron 400 Zino which we run MythTV on and use for displaying the recorded TV programs. Two years ago it was replaced by Iris, a Zotac Zbox AD03BR with the AMD E-350 Fusion Zacate with on-chip Radeon HD 6310M. It turned out that this CPU did not have quite enough oomph to play 1080p HD video, and the chipset had bugs in power management that made it unreliable waking up to record programs, so we reverted to Aurora. Aurora is not that old, 3.5 years, but it has its own power management problems.

In addition, we would like to use this machine as an audio playback node for FM radio, running most of the day. But Aurora is not exactly low power: 29 watts playing audio, compared to about 12 watts for the Zbox, so we have ended up using Iris for audio, only running Aurora for TV activities.

I would like to replace both machines with a new one that can handle both roles, reliably.

(Selection of Jacinth was not as well documented, since the emphasis was to get a machine in here fast and to get a lot of services running on it. But the issues were basically the same, except for a mistake, documented below, in the power consumption.)


There are several heterogeneous requirements for Iris.

Tentative System Selection

Which product lines are credible to provide the new machine?

I'm going to fixate on the CompuLab product line for the new machine. Of their offerings one of the fit-PC3 variants fits our needs best. Here is the justification for picking the fit-PC3.

USB Bus Structure

Currently we have a (relatively) new CompuLab fit-PC3 Pro acting as the home server and router, and a CompuLab Intense PC as a desktop workstation and compute node. So far we have been pleased with their performance. Both of them have three USB buses, each with EHCI (USB-2.0) and OHCI (USB-1.x) controllers, and one bus also has a pair of USB-3.0 capable ports and a XHCI controller for them. Both machines have a Face module in front with four USB ports: one or two on each of the three buses.

Here is the USB bus structure of the fit-PC3 Pro:

USB bus structure of the Intense PC. The Face module undoubtedly has ports on each of bus 1,2,3.

Either of these machines has enough USB bus capability to record two TV shows at once on different capture devices, plus to perform audio on the third bus, together with low-speed peripherals such as the keyboard, mouse and infrared remote control.

Wakeup Issues

The fit-PC3 Pro is always awake, but the Intense PC wakes daily from the realtime clock for daily housekeeping, as well as from USB wakeup signals, so I have a certain degree of confidence that it would also wake when needed to record TV. Experience on the Intense PC does not apply directly to the fit-PC3, but they have the same BIOS (Phoenix Secure Tiano), and so I am inclined to give it a pass on wakeup reliability.

CPU Power and Version Selection

How much CPU power is going to be needed? I have a simple benchmark that measures integer CPU performance by doing SHA-512 sums of files in the memory cache, and I/O performance by reading the whole disc. The composite score is shown, and its unit is Mbyte/sec. I also played some authentic 1080p content (MPEG-2) and measured the CPU utilization. The command line to perform it was simply:

gst-launch-1.0 playbin uri=http://aurora/video.mp2
A utilization of 100% would mean that both cores were maxed out (all processors listed have two cores). The marketing term Fusion Zacate means that the graphics processor is integrated on the same chip as the CPU.

Here are some more benchmark scores, including for the AMD G-T40E, which is the lower power processor available for the fit-PC3 product line. ss is the reported sample size, i.e. how many scores are averaged to give the reported number. Sources:

Hostname CPU Novabench ss PassMark ss Jimc's CPU%
Iris AMD E350 105 543 760 288 6.4 83%
Aurora AMD Athlon Neo X2 6850e 151 6 989 6 17.0 70%
(New) AMD G-T40E 72 4 482 1 -- --
Jacinth AMD G-T56N 113 19 778 13 38.0 46%
Diamond Intel Core i7-3517UE 314 2 3449 6 86.0 21%

Will the AMD G-T40E Work Out?

So, is the G-T40E going to be satisfactory for video playback? It's pretty clear that Novabench and PassMark correlate poorly with video performance while jimc's benchmark is better (but far from perfect). In particular, both Novabench and Passmark place the E350 and the G-T56N at almost the same CPU power, while on the actual task the G-T56N has at least twice the power, and even more on jimc's benchmark. The CPU utilization of the E350 is probably underestimated because it was dropping frames that the G-T56N was rendering.

Both commercial benchmarks give the G-T56N about 1.6 times the score of the G-T40E, corresponding to the clock rate of 1.65GHz vs. 1.0GHz. It's not really true that the CPU power scales with the clock rate, but in this case with the same motherboard and closely similar CPUs I'm expecting to see about 75% CPU utilization. That's a little high.

I found this Review of the Jetway AMD G-T40E Fanless Barebones Nettop By Lawrence Lee, 2012-05-29. This system is not going to win any prizes for gaming, but for video playback he got some interesting results, using Windows: H.264 1080p used 25% CPU (obviously hardware decoding), while Flash 720p used 56% (software decoding provided by Flash Player for Windows) and Flash 1080p ran the load up to 75% and dropped frames.

So it's not clear whether the G-T40E will be satisfactory: it could be spectacularly successful, or it could drag its tail and drop frames.

Since Jacinth is on all the time, I intended to get the lowest power CPU that was reasonable. I was targeting the power level of the G-T40E. Jacinth spends most of its time halted, waiting for a packet to come in, and power use while it processes that packet is nearly irrelevant, so I thought I might as well get the faster CPU. But I mis-read the specifications: the system with G-T40E uses about 10W at idle, while the one with G-T56N uses 19W. An opportunity now presents itself to rectify my mistake: buy a fit-PC3 LP with G-T40E and put it in the Jacinth role, and move the current Jacinth (G-T56N) to the MythTV role, replacing Aurora.

The original plan was to run both audio and video on the new machine. I get a significant power saving by retaining the present configuration of the 12W Zotac Zbox with AMD E-350 for audio playback. On the other hand, if I could put the audio on Jacinth that would be even better.

Picking the Machine

From the fit-PC3 specifications, the variant I'm targeting is this one. RAM and disc are not populated; what's shown is the maximum capacity.

Model Name fit-PC3i LP Barebone
Part Number fit-PC3i-D0-T40E-FM0
CPU AMD G-T40E, x86_64, 2 core, 1.0GHz
Chipset AMD Fusion Controller Hub A55E Chipset
RAM 2 slots SODIMM 204 pins DDR3 or DDR3L, up to 2x 8Gb
Disc 2.5in disc, 6GHz SATA
mSATA slot, 3GHz
Graphics AMD Radeon HD 6250 integrated with CPU; does H.264 hardware decoding but not Blu-Ray.
Display 2x HDMI 1.4a up to 1920x1200px 60Hz
Audio Realtek ALC888-VC2, 3.5mm analog stereo, and 7.1 channel S/PDIF on each HDMI, and 3.5mm microphone
LAN 2x Gbit 802.3 Ethernet
Wireless Not installed, may or may not be swappable. If provided it would be Realtek RT8723, Bluetooth on USB and 802.11bgn on PCI.
USB 4x USB-2.0 (rear) plus optional Face module (not included)
Mini-PCI 1 half-size slot, 1 full-size slot, or this slot can take mSATA
Features Auto-on, wake on LAN, wake on timer, PXE boot, watchdog, locking power connector, virtualization
Power 7W idle, 15W maxed out
Power (CPU only) 6.4W
Power supply 10V-15V; 12V 60W power brick provided
Temperature 0-50C limited by hard disc
Case Aluminum, passive cooling, smooth (not ribbed like the G-T56N variant)
Dimensions 16 x 16 x 2.5cm
In the box Machine, power brick, NEMA or EU power plug, HDMI to DVI adapter, 3.5mm to RCA audio cable
Warranty 5 years
Product Page fit-PC3 Product Pages

Pricing and availability: The fit-PC3's from Amazon have one DisplayPort and one HDMI (vs. 2x HDMI in the fit-PC3i above); and 2x eSATA (vs. no eSATA and a second Gbit NIC). Amazon items are sold by CompuLab and fulfilled by Amazon, a plus from our point of view.

For reference, the rear ports on the fit-PC3 (left to right) are: Antenna, DisplayPort, 2x eSATA, HDMI, RJ45, mini RS232, 2x USB-2.0, audio (mic), 2x USB-3.0, power, audio (out), antenna.

CompuLab fit-PC3i LP Barebone

$275 from CompuLab's USA (Florida) office. No Face module and I can't figure out how to order one. We have ordered from Florida before and it worked out.

CompuLab fit-PC3 LP Barebone

$275 from Amazon. AMD G-T40E 1.0 GHz dual core + Radeon HD 6250. No RAM, no disc, no wireless, no Face module. It looks identical to the fit-PC3i except different CPU, has 2x eSATA, and one Gbit NIC.

CompuLab fit-PC3 LP Diskless

$339 from Amazon. AMD T40E dual core 1.0GHz + Radeon HD 6250. Includes 4Gb (2x2Gb) RAM, no disc, has wireless, has 4x USB Face module. One reviewer is using this machine as a home theater PC (with Windows) with no complaints, 5 stars. This is the one finally selected.

CompuLab fit-PC3 Basic

$379 from Amazon. AMD G-T40N 1.0 GHz dual core + Radeon HD 6290. Includes 4Gb (2x2Gb) RAM, 250Gb disc, wireless, 4x USB Face module.

For the disc I'm going to get the Seagate Momentus 1 TB 5400RPM SATA 3Gb/s 8 MB Cache 2.5-Inch Internal Notebook Hard Drive, model STBD1000100. $82 from Amazon.

Amazon Order

CompuLab fit-PC3 LP Diskless, 4Gb RAM $429.00
Seagate 1TB Drive model STBD1000100 $81.99
Thermaltake Mobile Fan II $12.78
AmazonBasics USB 2.0 8x DVD Writer $32.14
Items $555.91
Tax $11.42
Shipping Free
Total $567.33
Date ordered 2014-02-21 (Fri)
Date promised (2 shipments) 2014-02-25 (Tue)
Order number 106-5321965-9205058
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