Bare Skeleton for Component Fit Test

After all the research and purchasing the parts, it’s time to put them all together to make sure they fit and work together. This first draft is only a test of component fit using a minimalist bare skeleton. It would not yet be a PC that I can lug around.

In addition to the aforementioned GPU mount, I had to design and 3D print a few other parts. The SFX12V PSU needed its own mounting bracket. As did the screen: I had the metal plate mating surface liberated from the monitor stand, but I needed to design and 3D print a part the metal bracket will attach to and in turn attach to the rest of the skeleton.

The skeleton itself is built out of Misumi HFS3 aluminum extrusions, which is 15mm by 15mm in cross section and well-suited to work with M3 screws and nuts. The nuts are the best feature of HFS3 – all I needed were standard M3 nuts. In contrast, HFS5 needed special Misumi M5 nuts that cost way more than standard M3 nuts.

The design of the skeleton is nothing special – a simple functional design that resembles the Yamakasi Catleap + HP Z220 luggable frame built several weeks ago at Tux-Lab.

I needed a laser-cut sheet of acrylic to tie everything together, so I packed up all the bits and pieces in their original enclosures for the trip to Tux-Lab.

Luggable PC Mark II parts

One laser-cut sheet of acrylic and a few hours of assembly work later, I have the first draft for Luggable PC Mark II! The components are left open and vulnerable but that’s not the point of this first draft. It’s just to make sure all the parts fit. Some minor fit issues were encountered but nothing terribly major.

I declare the fitness test a success. Onward to further refinements!

Luggable PC Mark II first draft

Researching PCI Express Extension Cables

Building Luggable PC (Mark I) determined that a direct GPU connection to the motherboard takes up a lot of space. For Mark II, a simple riser card would not fit. That leaves us with using a PCI Express extension cable.

A flexible cable allows significantly more freedom in placement. Given this freedom, I wanted the GPU cooling intake to face the same direction as the CPU fan cooling intake. This is better than a simple riser card, which would result in the two fan intakes facing opposite directions. To flip the GPU (and its intake) around, I’ll need a longer cable to take the circuitous S-turn.

One word of caution: most extension cables are sold to crypto-currency miners (*), who want the flexibility to pack as many GPUs into one computer as possible. Miners are not concerned with bandwidth and latency over the PCIe bus, but I am!

Hunting in the sea of products aimed at miners, my next task is to determine how much I need to pay for a decent quality cable. Amazon vendors sell cables for anywhere from $7 to $70. Some of the reviews left on the $7 cable (*) warned of destroyed components, making me jittery about going cheap. This cable has the potential to destroy a multi-hundred dollar GPU, a multi-hundred dollar CPU+Motherboard, or possibly both! I climbed up the Amazon price ladder until I found a $30 unit by “EZDIY” (*) with a significant number of reviews, none of which complained about destroyed components.

Then it came time to mount everything. The freedom of placement given by the extension cable also takes away the structural connection to the motherboard. I will need to design my own GPU mounting bracket with zero structural help from the motherboard mount.

The PC interface slot standard, built up over decades tracing back to the old ISA expansion cards, is quite a challenge to deal with. Optimized for mass-production with sheet metal, it is not very friendly to hobbyist 3D printing. But it’s a problem solvable with enough creativity in Fusion 360 and multiple test prints on the 3D printer.

Once it was all set up, I tested the configuration of both the extension cable and the 3D-printed custom GPU mount to verify everything works. It was a little jarring to see my GPU sitting on top of the box instead of its usual home inside.

(*) Disclosure: As an Amazon Associate I earn from qualifying purchases.

Researching PCI Express Riser Cards

When I take my Luggable PC (Mark I) around, I sometimes attract attention from like-minded PC builders who look over what I’ve done and offer helpful suggestions. I’m incorporating the Greatest Hits into construction of Mark II. We’ve covered two of them already: (1) Use a Mini-ITX motherboard and (2) use a smaller power supply. Now let’s cover (3) Use a PCI Express riser or extension.

The motivation comes from the fact standard PCI-Express GPU placement is very inconvenient for compact packaging. The motherboard and the GPU are placed at right angles to each other taking up tremendous amount of space. In Mark I I packaged components around the GPU the best I can, but it was far from ideal.

We need more freedom to rearrange these components and that can only come from putting in an intermediary between the PCI Express slot on the motherboard and the GPU connector tab, something that changes the nature of the connection.

First option is a PCI riser card like this unit (*) on Amazon. It gives us a 90-degree turn which is commonly used in servers to fit cards within a rack-mounted enclosure. Rack-mounted servers don’t usually need powerful GPUs, so these customers don’t run into the problem we have: Full power GPUs are two slots wide, the turn means it can only be used at the very edge of the motherboard or else the card will collide with the motherboard. For Mini-ITX boards, this presents an additional challenge because the GPU’s metal bracket, when turned 90 degrees and inserted to the one and only slot on a Mini-ITX board, will also run into the motherboard ports back plate.

Since a simple riser card wouldn’t work for this project, let’s look at extension cables next.

(*) Disclosure: As an Amazon Associate I earn from qualifying purchases.

Researching Small PC Power Supplies

A major goal of Luggable PC (Mark I) was to use components I already had on hand, which meant a full-sized ATX power supply unit (PSU) because I’ve never bought anything else before. For Mark II, I’m opening up the project budget to buy a compact power supply for the system.

There are plenty of small proprietary PC power supplies available in the aftermarket but low-production items will have limited selection and may be difficult to replace. The only units that were remotely interesting were the PSU for high-volume small form factor PCs of large manufacturers like HP or Dell. But they tend to be low powered units rated at 250W or less and also lack the power plugs needed to feed a power-hungry full size GPU.

So I started looking at the standardized PSUs. In the ATX power supply specification I found online (revision 1.31 dated April 2013) I learned there was a significant step in the evolution of ATX power supplies that shifted original focus from the 3.3V and 5V rails over to the 12V rails. This explains the “12V” suffix on some of these specifications – when a manufacturer names their ATX PSU as a “ATX12V” power supply, they declare 12V focus on power capability.

However, the first three letters still describe the physical form factor. I didn’t find many CFX12V or LFX12V units available. TFX12V and FlexATX12V are more common but they are equivalent to those HP/Dell PSUs with low wattage rating and no PCI-Express card power plugs. We want something smaller than ATX12V, so that leaves SFX12V.

Thankfully there seems to be a healthy SFX12V niche in the ecosystem. They do tend to be lower in power rating than full sized ATX12V but I expect 450-600W to be plenty. And they have most of the power plugs of a full ATX12V unit, including those valuable PCI-Express power plugs.

The power plugs actually present a bit of a problem: any wires I don’t use in my system is dead weight and taking up space. In theory this can be resolved with a SFX12V PSU with modular plugs and wires. I ended up getting one modular (Corsair SF450) and one non-modular (FSP Group FSP450) SFX12V PSU to experiment with.

On the physical form factor specification, SFX12V was only a few centimeters smaller in each dimension relative to ATX12V. But those numbers understate the reduction in physical volume. When I pulled them out the box I was quite pleased at how compact they were. This is going to be a tremendous help in keeping Mark II slim.

ATX12V and SFX12V power supply units side by side illustrating difference in volume.

Lenovo L24q-20 Monitor: Core of Luggable PC Mark II

Once I decided the Luggable PC Mark II project will be built around a retail available 24″ monitor with QHD (2560×1440) resolution, it narrowed down the list of screens I need to keep an eye open for deals. A few weeks after the decision, a promising candidate popped up: Best Buy put the Lenovo L24q-20 on sale for $170, a 15% discount from its usual $200 price.

The specifications look promising. The panel type is IPS, which is great as I had expected to find only the TN panels in the lower price range. The physical dimensions are impressively minimal, with a very thin bezel on the top and sides. More than half of the back side is flat, making it easy to pack computer components in that space. The shipping weight is light, implying either the screen is lightweight (good) or that they really skimped on packaging (not as good).

The monitor had few inputs (one HDMI port and one DisplayPort) but I only need one so that’s fine. I was less thrilled with the fact all the plugs (video and power) stick straight out the back instead of pointing downwards. The latter would have made it easier to package everything in a slim enclosure.

The other disappointment is the lack of standard VESA mount points. Their presence would make chassis integration straightforward, but it is not itself a deal-breaker. It depends on whether I can work with the nonstandard mount.

Having done all the research I could over the web, I went into the local Best Buy for a look at the display unit to learn things they don’t put on the spec sheet.

Item #1: Power. I could tell the monitor uses an external power converter, but the specifics were not listed. Ideally the monitor can run on 12V DC because then I could rewire it to draw that 12V from the computer power supply. Sadly this Lenovo takes 19V. On the upside, its DC power converter is very small so I think I can package it in my enclosure.

Item #2: Mount. The final make-or-break factor… how the monitor is mounted to its stand. Again, not something listed on the spec sheet. I turned the Best Buy display unit around, found the release latch, and separated the monitor from the stand. I saw the mating surface of the stand is a metal bracket fastened by 7 Philips screws. I can remove those 7 screws and use the metal bracket in my own chassis as attachment point for the monitor.

Yes, I can work with this! I put the display unit back together and grabbed a box to take home. I bought what turned out to be the last new unit in stock.

Lenovo L24q-20 monitor stand with the metal mounting bracket removed to show the 7 fastener locations. 4 machine screws into metal, 2 on the left and 2 on the right. In between them, 3 self-tapping screws into plastic. The bottom two round objects are not screw locations – they are posts to help locate the mounting bracket.

New Project: Luggable PC Mark II

I’ve been using my Luggable PC for about four months. It was originally built with retired computer parts, but the concept worked so well I transplanted the guts of my main desktop tower into the enclosure and now it is my only computer. I use it at home connected to my Monoprice 28″ UHD monitor (predecessor to the current Monoprice 28″ UHD monitor) and when I want a computer on the go, I close the screen and take it with me.

Luggable PC Mark I

Unfortunately that means leaving the UHD (3840×2160) monitor behind. While the built-in 17″ screen (with the flip swivel hinge I’m proud of) is a respectable 1920×1200 resolution, it feels quite cramped when I’m spoiled by a UHD screen at home.

So that became the motivation for a sequel: the Luggable PC Mark II. The main thrust of the project is a larger, higher resolution screen. And this time, I want to build the chassis around a monitor available at retail, instead of a salvaged laptop panel like the Mark I. Being specific to a salvaged panel is not very friendly for others to build their own. Tailoring Mark II to a monitor people can buy would be better.

So the next question is size. Tux-Lab experiments with the Yamakasi Catleap monitor taught me 28″ is too big to be easily portable. Looking over the computer monitor market for sizes between 17″ and 28″, the 24″ size seems to be the best one to experiment with. It is a popular size with a wide selection of makes and resolutions up to and including UHD if the budget allows for it.

And while external dimensions vary, they are mostly less than 14″ high and 22″ wide. Why these dimensions? They are the limits for carry-on luggage at United Airlines, which seems roughly representative of (or possibly more restrictive than) most airlines. I still hold the dream a Luggable PC can fit in an overhead compartment. (Assuming I can get it past TSA.)

There’s no point in a 24″ FHD (1920×1080) monitor since that’s no better than the screen I already have.  My project budget is not daring enough to jump straight into a 24″ UHD monitor price tag. So the hunt is on for a 24″ QHD (2560×1440) monitor that I should be able to find for well less than half the price.

Gigabyte Z270N-WiFi and its F1 Firmware

When I embarked on the Luggable PC project, the primary goal was to build a computer using components I already had on hand. This translated into the requirement to accommodate full-sized desktop PC components. Now that I’ve used it for a while and started to like carrying my full-time computer around, I’m building up for an upgrade. This time, instead of building a chassis around components I already had, I will buy smaller components with the intent of assembling a new luggable chassis.

First up: The motherboard. Out of all the commodity form factors, the best balance of small size, computation power, and reasonable price is the Mini-ITX form factor. I’ve already worked with a few boards of that form factor, but none with leading edge components. This changes with the purchase of a Gigabyte Z270N-WiFi.

Image by Gigabyte

The specifications of the motherboard looked great on paper. In additional to the small Mini-ITX form factor, the features important to my project are:

  • Support for Intel’s latest Kaby Lake generation of processors
  • M.2 slot for SSD
  • PCIe x16 slot for full-power GPU
  • Wireless networking

Factors that were not critical, but used as tie-breakers against its competition:

  • Dual-port Intel gigabit wired Ethernet
  • 6 SATA ports
  • USB-C port
  • Bluetooth

Looks great on paper! Sadly in reality the motherboard made a very poor first impression due to the onboard firmware. It was heavy on flashy looks and light on usefulness. I ran into many problems with basic functionality.

Example 1: The USB mouse support was useless: I could move the cursor around with the mouse, but clicking has no effect.

Example 2: Upon startup, it shows a full-screen Gigabyte logo (basically an advertisement) that I find annoying. If I select the firmware option to disable the logo, the motherboard no longer boots: I have to reset the firmware settings via jumper to get back to square 1. This was such an unexpected thing that it took three resets before I determined it was the logo setting that caused the problem.

So the “F1” version of the motherboard firmware was a disaster. Fortunately by the time I bought the board, Gigabyte has released updates and is currently on “F4”. Upgrading allowed me to disable the Gigabyte advertisement and still have a functional computer, in addition to addressing other functional annoyances.

This motherboard was clearly pushed out the door with incomplete firmware and the expectation on users to upgrade. I now have a good motherboard, but there’s a sour taste in my mouth from the bad out-of-box experience.