How to build a dual-core PC for under $50

I’m happy to admit I love the Raspberry Pi. We first covered the tiny single-board computer (SBC) within the pages of APC back in 2012, not long after it first hit the market. I even developed a Linux operating system designed for the Pi called ‘APC PiLinux’ just before Raspbian OS hit the scene. The Pi is a great low-cost choice for DIY or ‘embedded’ applications and its original intended use – education. But as the basis of a media centre, I must admit I’m more than a little surprised that it’s still getting so much air-time.

The specs of the Raspberry Pi – even the latest top-drawer Model B+ – aren’t spectacular by any stretch. Broadcom’s BCM2835 media applications processor is built around an old ARM1176JZ-F single-core engine clocking in at 700MHz and with 512MB of RAM are serviceable, but not overly generous. Again, for its original education focus, the Pi still fits the bill nicely.

But while its general-purpose application performance isn’t going to worry Intel or AMD, the icing on the cake for media enthusiasts is the built-in VideoCore IV engine that delivers H.264 (and MPEG-2) video playback at up to 1080p resolution and 30fps.
Not to mention the Pi’s legendary low price.

Low-cost alternatives available

hubIn the UK and US, a good deal of the Pi’s following comes from that low US$25 price tag for the stripped-down Model A version (US$35 for the Model B/B+). But in Australia, local distributor, Element 14, encourages personal shoppers to buy through a list of local resellers, where the Pi B+ sells for closer to $50. At that price, it’s still a decent little SBC, but it must be said – it’s not the only similarly-priced tool in the shed.

Around the same time the Pi launched in the UK back in 2012, we began seeing the arrival of compact USB-stick mini PCs from Asia. These tiny little computers typically featured a faster 1GHz single-core ARM Cortex A8 CPU, either 512MB or 1GB of RAM, up to 8GB of on-board flash, powered by Android 4.0/Ice Cream Sandwich OS. Throw in at least one USB host port, HDMI and you had a super-compact Android PC. They even came with a case!

Since then, the mini PC market has boomed, although more obviously in Asia. Personally, I still find it astonishing that these little devices haven’t found more of a home in the mainstream. Today, you can pick up a dual-core mini PC with Wi-Fi, Bluetooth and Android 4.2/Jelly Bean for under $40 on eBay. They’re essentially a budget Android tablet without the battery or screen – and compared with the Raspberry Pi, you’re getting considerably more horsepower.

The USB-stick styled MK808B is one of the cheapest options now, featuring Rockchip’s RK3066 dual-core Cortex A9 CPU clocking in at 1.6GHz. This is an impressive little chip that also packs in ARM’s quad-core Mali400MP4 GPU. It’s roughly on par with a Samsung Galaxy S2 smartphone for performance – not ‘blink and you’ll miss it’ type stuff, but it won’t have the grass growing under it, either. There are a few variations of the MK808B floating around, but the best version has 802.11n WiFi and Bluetooth 4.0, along with Android 4.2/Jelly Bean OS, 1GB of RAM and 8GB of on-board flash. The MicroSD card can handle up to 32GB and it has two USB ports – one Type A and another as OTG, not to mention HDMI output. Look hard on eBay and you’ll see a couple of sellers flogging it for under AUD$40.

mk808bInterestingly, it’s not the only alternative either. The USB stick-style mini PC isn’t a bad option, but can be a little awkward on a desktop. The alternative is the TV set-top box (STB) style that looks more like a Western Digital WDTV Live media player, but with extra versatility. This style of mini PC has been around for a while, too, and prices on entry-level models have recently dropped down to below the US$40 mark. The benefit here is that you still get the usual HDMI and 802.11n Wi-Fi options, but in addition, you can usually count on two USB host ports (ideal for keyboard and mouse without needing a hub), composite video output, optical S/PDIF audio and wired Ethernet. Plus, Android 4.2/Jelly Bean OS.

The drawback? The cheaper models typically only include Allwinner’s 1GHz A20 CPU – it’s dual-cored but based on ARM’s less-powerful Cortex A7 core design. However, compared with the Raspberry Pi, it’s still out in front.

Quad-core and beyond

Beyond the dual-core offerings, quad-core models now regular sell for under US$60. At this price, they’re almost universally powered by Rockchip’s quad-core RK3188 ARM Cortex A9 CPU. Initial batches of some mini PCs with this CPU saw user complaints regarding performance issues, but later user-install firmware updates appear to have fixed most concerns.

If four cores aren’t enough for you, Allwinner has just announced a new A83T eight-core Cortex A7 CPU design with built-in PowerVR SGX544 GPU. As impressive as that sounds, keep an eye on Rockchip’s RK3288 CPU – it’s based on the brand-new Cortex A17 core design from ARM, hitting 1.8GHz and including ARM’s equally-new MaliT764 GPU.

The Cortex A17 is 60% faster, clock for clock, than the Cortex A9 straight off the bat, says ARM, which isn’t a bad place to start. It’s now appearing in new Android-powered STB mini PCs just this side of $100 on eBay.

Mini PC hacking

paragonFirmware updating or hacking of mini PCs is a popular community sport these days. Sites like FreakTab regularly feature updated Android firmware for various devices that either fixes bugs or even improves upon the official ROMs. The install process typically involves loading the firmware onto a MicroSD card, installing the card into the mini PC and rebooting it into recovery mode, where the firmware basically installs itself.

That said, the firmware flashing routine is different for every device, so do your own research before you bite the bullet and have a go yourself. But from first-hand experience, upgrading to an improved ROM can make a significant difference to a mini PC.

While most ROMs are Android-based, there are an increasing number of Linux ROMs now appearing. Linux has supported ARM CPUs for some time now and a number of mini PCs now support ARM-versions of standard Linux distros. You’ll find major distros such as Debian and Ubuntu also have repository support for ARM builds. That essentially turns an ARM-class mini PC into a genuine desktop replacement – and for well under $100. For example, mini PCs powered by Rockchip’s RK3188 quad-core CPU can now boot Ubuntu 12.04 LTS via a MicroSD card. What’s more, it doesn’t interfere with the on-board Android ROM. Plug the card in and reboot to launch Ubuntu, remove it and reboot to launch Android – it doesn’t get much easier than that.

While Linux will run on these devices, there has been a problem with a lack of device drivers, particularly to handle the ARM Mali400 GPU. However, in recent weeks, this situation has improved and although still very new, it looks as though accelerated GPU support for devices running Rockchip’s RK3188 CPU and Linux is now available. Head to www.linuxium.com.au for details.

Mini PC wireless NAS

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Since these mini PCs all come with Google Play, they’ll run the vast majority of apps available on the app store, but there’s an amazingly diverse range of apps that are well suited to mini PC use.

One of my favourites is turning a mini PC into a wireless NAS – and it’s not as silly an idea as it might sound. Commercial network-attached storage boxes from the likes of Synology and Qnap are powered by a similar (and sometimes, slower) grade of CPU. For example, Synology’s current single-drive DS112j runs a 1GHz version of Marvell’s single-core Kirkwood-series chip, based on the old ARMv5-TE architecture (by contrast, the Cortex A9 is a newer ARMv7-A form).

Over the last couple of years, the majority of the mini PCs I’ve tested, used and mucked around with have root-access already baked in and for creating a wireless NAS, that helps immensely. Sure, a NAS build of this type obviously won’t include RAID support, but it should match most single-drive NAS boxes (and possibly even go past them!).

Building up the NAS

rk3188
Starting with a mini PC and even adding a 32GB microSD card, you’re not going to have more than 50GB total to play with, so what’s needed is a way to bulk up that storage – ideally, using a compact portable hard drive.

And the trick is to use a good-quality powered USB hub, preferably one that’s USB3.0-ready – not necessarily for the speed, but for the extra power handling. Mini PCs are mostly USB2.0 but generally can’t supply enough power on their own to run a bus-powered portable drive and too many budget powered hubs I’ve come across are bundled with lame 5V/1A power bricks that might be fine for a keyboard and mouse, but hopeless for powering a portable drive.

Of course, if you have an externally powered hard drive, that should solve the problem, albeit with a larger footprint.

NAS software

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Turning an Android device into a server of any kind does sound weird, but there’s a surprising amount of server-functionality software on Google Play to make it happen.

A NAS box is primarily about storage and one of the simplest apps I’ve seen for turning an Android device into a network storage server is Samba Filesharing. Samba is the Linux tool for network communications with Microsoft Windows and here, it enables a mini PC to appear as a shared network storage drive on Windows Explorer. Samba Filesharing is free, but it does have a couple of drawbacks – apart from needing root access, it can only support two storage devices (internal storage and one secondary external source) and that second partition can only be FAT-formatted, which limits its usefulness.

However, if you’re prepared to cough up $2, there is an excellent alternative on Google Play called Sambadroid. It’s free to download, but this free version only gives you network access to your Android device’s internal storage. Upgrade to the Pro version via a $2 in-app purchase and you can add in external storage options.

There’s only one minor hitch – early versions of Android don’t support Microsoft NTFS-partitioned devices. But again, there’s a quick fix for this too – grab hold of Paragon’s exFAT, NTFS and HFS mounting app, free on Google Play. This app happily mounts NTFS-formatted drives within Android that you can then add as shares to Sambadroid.

Finding Sambadroid on Windows

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The only minor annoyance we’ve found with Sambadroid is that it won’t automatically appear in Windows Explorer the way Samba Filesharing does (at least not with Windows 8.1). But all you need to do is fire up Windows Explorer and in the address/folder bar, type in ‘\\sambadroid’ (assuming you haven’t changed the name in the app settings, in which case, you replace ‘sambadroid’ with your chosen NetBIOS name) and the shares should quickly appear.

While we’re assuming you’ll use this safely behind a firewall/NAT router, Sambadroid does have support for users and passwords to boost security if that’s an issue for you.

Still, the end-result is you can have a mini PC with a 500GB or larger hard drive connected via a powered USB hub and acting as a wireless NAS box. You won’t get RAID support through Android, but unlike most other NAS boxes, you’ll also end up with a general-purpose Android PC with access to over one million apps in Google Play that can play games, movies – even do real work.

Buyer Beware

Since these devices are usually manufactured and sold by small no-name companies and retailers, don’t expect the level of support you’d get buying a $1,000 PC. Like most things, you get what you pay for. That’s not to say mini PCs aren’t worth the effort – on the contrary. It just means you need to be prepared for some DIY and search out your own solutions to problems (the mini PC community is a great resource).

The other thing we’d stress is that if you buy a mini PC from eBay, you may end up with a US or EU-plugged power brick. Even if you’re supplied an Australian-plugged brick, for safety, we’d recommend replacing it with a local Australian-approved power supply unit.

Mini PCs using USB power can be juiced with any USB power adapter with a two-amp (2A) current rating. But for mini PCs using a brick that terminates with a barrel-type DC power connector, look for a multi-adapter plug brick rated to the same voltage, current and plug polarity as the original. You can usually find these at Jaycar Electronics stores.

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  • Monty Woods

    This is a great article. It isn’t skewed toward any hardware mindset, gives us many many hw choices that I had not been even thought of. Sometimes less is better. How much remote computing actually requires 4 cores or cost more than a project should? Plus there are the power requirements, connectivity to network and other storage needs, being innocuous at times. SDR is a great spinoff of technology that was there for a long time but was undeveloped. But now there are so many new chips that control power and communications and many more things. I look at the automobile network (OBD-II) that has almost NO developed hardware/software to assist the driver in efficiency, engine control and using fuels that are deliberately disabled by collaboration between oil co & auto industry, etc..

    Technology for disabled veterans could be a godsend for us, I need text to speech but the technology isn’t there yet for all the different pronunciations of a word depending on context, verb vs noun vs usage. Kindle has done a decent job in reading most text files but cannot read any pdf files. Kindle has been able to enjoy reading again even with visual impairments. The problems I see is the compilers & code produced to use the multi-core /threads. What good is 4 cores if the OS launches from only one core.

    The current batch of Raspberry Pi model B+ come with either 512mg or 1Gb of ram on the card itself. This batch uses Broadcoms 4 core cpu and need few add-ons to make a full blown Linux or Windows10 computer. It has MicroSD connector for OS,4 USB for storage, printer ,Wi-fi., etc. there is a separate camera & separate display connectors , 1 Ethernet,and additional HDMI display port ;micro usb for power + separate barrell power wart connector. and all the GPIO pins. I saw
    part of an article saying that the max read speed of Raspberry Pi Model
    B+ is 30Mhz. Getting SD cards that are faster than 32
    Mhz is a waste of money! Was this true or more misinformation? Some info on Raspberry Pi Model B+ hasnt been published or hasn’t been documented yet. Like GPU engine info. display. The Pi boards are truly revolutionary and will jump start other hardware to market to fill the niches that will develop