Log Been away for a while from SFF, new PC needs to be small! Let's go.....

[mbrown278]

Hi all, I previously have designed and attempted/completed laptop style/other sff builds, but they have been too bulky for me really take anywhere. So I ended up building a massive PC, and got a laptop, and use both. I have really been wanting to approach the idea again of a small does everything I need it to type of build.

Requirements: Can be taken to work when working in the office (including powerful enough for the VR app immersed), can be used at home for VR and for working at home and agin using the app immersed.

Currently I have a 10600k, an RTX 4090, 32GB of ram, with a Asus Tuf z490 motherboard, and 2gb M.2 SSD. In a massive case with 6 x 140mm fans and an 850W PSU.

From searching for mini itx boards, or thin itx, or mini PCs which are capable of adding a dedicated GPU, it almost seemed like the mini itx route was the only way, but previously this proved too big. Really I am looking for something that can take a higher end 13th or 14th gen Intel CPU or similar level AMD.

After a lot of looking, I managed to find a Lenovo Thinkcentre M90q gen 4. I can spec it with an Intel 13900 (which looks to be slightly reduced clock at 5.4GHz instead of 5.6GHz. This is significantly more powerful than my 10600k, or 5800H in my laptop.

Lenovo Thinkcentre M90q Gen 4

The Lenovo PC I have spe'd with 32GB of 5600MHz ram, and no SSD, as I will use my own 2TB M.2.

The Lenovo build so far is just under 1.2L.

Next is the main bit I am excited by (sad I know). The Lenovo PC has an 8x 4.0 PCIe slot! Yes it is just 8x, but that has the same transfer speed/capability of my current 3.0 16x slot my 4090 is in on my ATX motherboard.

So I have two thoughts, either I will build a case to house the Lenovo PC, and a GPU, or I will mod the case so it has a PCIe connector/extension accessible, allowing me when I get home to just plug in my 4090 (with its own PSU) to the Lenovo thinkcentre. Either way, I would consider mounting the power supply for the Lenovo device + GPU, or just Lenovo device in any case itself, and adding a small screen. It only needs to be small, as I will use a pair of xreal airs, a work display, or a vr headset for work/home/gaming. I have ordered the immersed VISOR, so that will become my main multiple displays.

I feel much better about such a low volume starting point, and can consider using various powersupplies depending which route I go down.

Lenovo ordered, and I'll know more when I start testing Any thoughts/suggestions welcome

 

[mbrown278]

After some more researching, I have decided to power the computer with a battery, and after looking at available powerbanks, I decided to reduce the order from a 13900, to a 13900t. There is a very slight drop in performance, but nothing I will probably notice unless benchmarking.

Problems/solutions so far:

- Finding a powerbank that can provide up to 135w via usb C to a Lenovo slim rectangle connector. I found the Anker Prime 250w bank which can provide a single USB C port supply of 140v, but only at 28v.

From looking at power delivery standards, the 20v needed can only be provided at 100w. Charging with two USB C ports can provide up to the wattage needed. However, combining two USB C ports for power is difficult. The Anker solution is also too deep for what I had intended at 5cm deep - The Lenovo PC is 3.5cm deep, so I am hoping to have a power bank thinner than that to prevent the laptop/pc getting any thicker.

After searching and looking at various power banks, I found the XTORM Titan Ultra 200w, which fits just about all requirements. It is just 3cm thick. It can provide 200 watts in total across its USB C ports, and has a good capacity at 27000mAh. It is 19cm long, so shorter than the monitor I am looking to use (13.3 inch, 19.5cm x 30.5cm x 1.1cm.) There are two USB C ports capable of 140w (although at 28v), and two capable of 30w. I doubt the lenovo can stretch to 28v from 20v, so I will be stuck with using two usb C ports. I would however like to use passthrough charging, and have a 65w PD charger, which I will have to use in one of the 140w ports, leaving a 140w (100w at 20v) and two 30w ports. So I will need to combine a 100w and a 30w USB C port to get close to the 135w power adapter the pc comes with. I will be testing the power draw though to see how much overhead the PC has within that 135w. It might be that at maximum load, the wattage is under 100w, which would make things significantly easier.

- Next difficulty, is combining two USB C ports if needed for power. There are no adapters, and there are concerns about the same voltage/supply being given. To get around this, I will be looking to use a decoy USB C trigger. You can get these with switches on, to set the voltage, but I prefer a fixed option so it can't be accidentally changed in transit or something. So I have looked for 20v fixed options, which can do up to 100w, and I would then enclose them in a case. I found these though which provide a case with it, are fixed, can go up to 100w, and have the wires already on to combine the two 20v feeds.

I would then have two of these with two USB C cables (if I do need above 100w). I solder over the 20v connectors to set it as fixed 20v. When I combine the two feeds, it will be in parralel, so the voltage across both won't be added together (which would make roughly 40v, double what is needed).

- Next, after combining the two feeds out of these 20v decoy units (which tell the power bank to provide 20v), I would then connect it to one 7.9 x 5.5mm barrel connector with this.

and as a final touch, connect that barrel connector to a right angled Lenovo slim rectangle connector.

I do still need to confirm the barrel connector and Lenovo right angles adapter I'm looking at can go up to 135w. If they can't, then I might have to get a 135w adapter, and cut the wire and join it to the decoy unit wires.

In terms of size, I am hoping to make it no larger than the footprint of the monitor - 19.5 x 30.5cm. From a quick look at the dimensions of all parts, I am aiming reallistically somewhere around 20cm x 30.5cm x 5cm. This will make it around 3.05 litres, which includes the volume of the screen, and the screen dimensions in the overall size.

I will then be looking to make a PCIe extension which will sit flush with the edge of the case, allowing me to connect my 4090 with its own PSU when at home.

For peripherals, there are loads of portable/foldable keyboards both with and without mouse pads, and I already have one, so that is sorted