Taking Apart the Vision HT
Like the exterior, everything was tidy under the 420D's hood. Asrock designed a neat cable system for delivering power and data cables to the optical and hard disk drive. Mounted above Asrock's HM87-HT motherboard is a HGST 5K1000 1TB 5400RPM hard drive with an 8MB cache valued at ~$80 US, along with the Lite-On SATA slim slot-load DVD+/-RW drive (DL-8A4SH).
The latter drive supports read speeds of 24x CD, 8x DVD and write speeds of 8x DVD+/-R, 8x DVD+RW, 6x DVD-RW, 6x DVD+R DL and 24x CD. It also features a relatively small 2MB buffer with access times of 180ms for DVDs and 180ms for CDs.
At the heart of the Vision HT 420D is the mobile Intel Core i5-4200M, which is based on Haswell, runs at 2.5GHz (3.10GHz via Turbo Boost) and has two cores (with Hyper-Threading) as well as a 3MB L3 cache.
The board features a pair of DDR3 SO-DIMM slots but only one is populated using an ASint DDR3-1600 4GB module. Upgrading the Vision HT 420D memory will require an additional 4GB module for an 8GB capacity and we highly recommend doing so for the cost of just $40. In fact, we're shocked Asrock has only included a single module, as the Core i5-4200M supports dual-channel memory. Using a single module limits the processor to a single-channel mode, crippling performance.
For networking, the Vision HT 420D uses the Broadcom BCM57781 Gigabit Ethernet controller -- a popular choice for Asrock recently -- in addition to a wireless 2T2R 802.11 a/b/g/n/ac PCI Express Half Mini Card.
Asrock has also included a Realtek chip for audio, using the company's tried and true ALC898 8-channel audio codec with THX TruStudio Pro. The TruStudio Surround technology expands your stereo content into surround sound and the TruStudio Crystalizer technology restores the compressed sound source, letting you hear every detail in surround sound.
The Asmedia ASM1442K chip outputs high-speed TMDS level shift for the HDMI and DVI outputs on the motherboard while the Nuvoton NCT6776D IC has helped Asrock achieve the EuP2.0 standard, which indicates that the total AC power consumption of the system is under 0.5W when turned off.
Previous Asrock Mini PCs with USB 3.0 have employed third party controllers such as the NEC D720200F1. However, Intel finally included native USB 3.0 support with Ivy Bridge and its 7-series chipsets.
This native support was carried on with Haswell and 8-series chipsets, with the HM87 chipset (what you'll find inside the Vision HT 420D) featuring support for six USB 3.0 ports.
The Vision HT 420D comes with a single 2.5" 1TB hard drive and a second 2.5" drive can be mounted under the primary. Early internal designs of this chassis required users to remove the optical drive and primary hard drive before the optional secondary drive could be installed.
This inefficient approach has since been corrected so it's now possible to quickly install a second hard drive without removing any other hardware. Asrock also include a cable that connects from a special power connection on the motherboard to the second hard drive.
This opens the possibility of purchasing a second hard drive for more than a terabyte of storage in this tiny PC. Alternatively, an affordable low capacity boot SSD drive would be a nice option here.
The cooling setup is similar to that used in laptops, which is not all that surprising as the Asrock Vision HT 420D uses a mobile Intel processor. The CPU and HM87 chipset are cooled via a large silver aluminum heatsink with a copper base that is actively cooled via a small 65mm blower fan which remained very quiet throughout the testing phase.