Question Limitation of micro ATX in small form factor server cases

Oldcompsci

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I continue to encounter limitations regarding the ATX and mini form factors available today.

The biggest being the width of the ATX, microATX and DTX motherboards (243 mm width) ability to fit in smaller cases

The "mini" sized motherboards (170 mm width) are a great option for these smaller cases but the expansion slot limitations with ITX and DTX form factors are a nonstarter

I'd like to know the community interest in getting a mini (170mm width) motherboard with the same expansion slot options of the microATX motherboard (243 mm)?

These size motherboards could be "drop-in" options within cases designed for micro ATX, but with more room due to the decreased width of the board.

The board would be 244mm x 170mm in size ... I'd call it mini-ATX to keep with the other naming convention of the mini sized board (i.e. 170mm).

Picture of the idea posted here ... https://drive.google.com/file/d/1KC2yWqZ5RdlH0zVV-OBn5zfkz9gA8ICZ/view?usp=sharing
 

tennis2

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DTX was my first thought here.

There's been a few mATX mobos here and there that pop up with narrower width, but they're limited to 2 RAM slots.

I had an idea a while back, 4 SODIMM slots stacked in a 2x2 configuration that actually takes up the same amount of space as 2 DIMM slots. since a SODIMM stick is almost exactly half the length of a DIMM stick. That could be applied similarly to keep board width down. Imagine the pic below, but with 2 SODIMMs in each RAM slot basically (single latch top and bottom and a fixed double-sided "latch" in the middle)



Also, there's this config:


I think either way you slice it, you're gonna need SODIMMS to keep the width down.
 

Oldcompsci

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Apr 30, 2019
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DTX was my first thought here.

There's been a few mATX mobos here and there that pop up with narrower width, but they're limited to 2 RAM slots.

I had an idea a while back, 4 SODIMM slots stacked in a 2x2 configuration that actually takes up the same amount of space as 2 DIMM slots. since a SODIMM stick is almost exactly half the length of a DIMM stick. That could be applied similarly to keep board width down. Imagine the pic below, but with 2 SODIMMs in each RAM slot basically (single latch top and bottom and a fixed double-sided "latch" in the middle)



Also, there's this config:


I think either way you slice it, you're gonna need SODIMMS to keep the width down.
I like the 4 SODIMM concept. Wasn't too worried about the memory ... was more interested in just the expansion slots. Using SODIMMs could definitely address the only two slot challenge with 170mm motherboard. That said, the longer length of the mini-ATX may make for room for regular DRAM ... although I believe distance from the processor is critical so the rearrangement needs to be done carefully. My though is that NVMe based drives could move down to the area that 's available with the longer length of the board (assuming not every expansion slot is x16 in size)

The only other option I've really found is to use a Single Board Computer with a passive PCI-e backplane. Problem there is it is extremely expensive and processor support is more limited.
 

tennis2

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Oldcompsci

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I'd be looking for one x16, one x4, and one or two x1 if they could fit. That said, NVMe SSDs aren't my concern, expansion cards are.
 

Oldcompsci

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This is what I'm working with right now ...

https://www.amazon.com/gp/product/B006UACQB0/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

- using a microATX board makes using the 3.5" HDD mounts difficult/impossible. The power and other plugs on the board interfere with the 3.5" HDD's in the the lower slots.

- using a mITX board fixes the 3.5" HDD issue but limits the expansion card options.

- want to have an option for a 244m x 170mm board that gives me more room in the case but also provides more expansion slots. This would allow the ability to use all the 3.5"mounts (8 total, 4 on each bracket) and support the expansion cards I want to use.

244 x 170 is a viable size since it would be a drop in for existing cases that can support microATX without any modification.
 
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tennis2

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Unsure if you saw the addition to my previous post, but assuming this doesn't work for you?
https://www.asrock.com/mb/Intel/H510M-HVS/index.asp#Specification
2 inches narrower than your "standard" mATX mobo. Only has 4 SATA ports though.

Again, you get into mATX boards with 2 RAM slots that are generally "low-end" so having an abundance of PCIe slots on that reduced width is uncommon.

Speaking of which, is there a specific platform (chipset) that you're intending to use here. Are we talking consumer-tier hardware, or are you requiring stuff like ECC RAM and the like (rackmount chassis).

I'm trying to cling to readily available aftermarket stuff instead of delving into the world of OEM mobos (foxconn, etc) that may not be purchasable in single/limited quantities or by non-business accounts.
 
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Oldcompsci

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This is mainly consumer/workstation end concern. Myself and a lot of other folks I work with have their own "short rack" setup to do "dirty" software prototyping, rendering and other things at home and at work (if it's open). AMD chipsets are the choice right now. RAM is a consideration, but not really a show stopper ... dual 64GB DDR (128 GB total) can fit the bill ...

Since the 244 x 170 would drop into existing microATX cases, it seems like a logical option if manufacturers can adopt it for production.

Usually when I'm looking at server sized options, I want more ram than 2 slots can handle. I want more drive options and other things which drives a bigger case to support server hardware and this "problem" goes away.
 

tennis2

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Since the 244 x 170 would drop into existing microATX cases, it seems like a logical option if manufacturers can adopt it for production.
Those 198mm wide mATX boards are the narrowest I've seen. Aside from DTX boards which are increasingly rare, that's really your only option for >1 expansion slot. I'm not sure why your specific mATX case would even include the drive bays if the lower bay is blocked by the mobo, but again, lopping 50mm off the "standard" mATX spec with the boards listed above could be all you need to fit the extra drives. Might want to check.

Getting 4 RAM slots on a board that narrow is physically impossible (in the standard vertical orientation) unless you find a board that uses SODIMMs. That's also rare (unfortunately). The X299 mITX example I gave was a rare bird, but was afforded the unique design flexibility by the premium price tag expected of the platform (retail availability aside)

As it seems you aren't buying under a major business (datacenter) umbrella of a large quantity order, I'm going to go ahead and say your chances of commissioning the "custom" board you're describing at anywhere near a reasonable amount of $$ is near zero. If you need >64GB of RAM (AsRock B560M-HDV) and that reduced-width 198mm is still too wide for the mATX case you linked, time to consider:
  • a different case
  • something other than 8x3.5mm HDDs.
    • 2.5" HDDs/SSDs in the obstructed bays
    • M.2 SSD(s) - If you go with an Intel CPU that has an IGP, you could use the x16 slot for a 4 or 5 way M.2 SSD adapter, plus the 1 M.2 slot on the mobo.
    • Larger capacity HDDs to reduce the total required (since you may be limited to 4 SATA ports if you don't use an expansion card)
 
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Oldcompsci

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If venders can build to the 170mm spec, and they do with a pretty wide variety of mini-ITX and smaller boards, and since DTX and mini-DTX is a dead option, mainly due to the lack of expansion, I don't see any reason they don't give a 244 x 170mm a shot. Still fits within their existing PCB manufacturing size, gives users the expansion they want, and provides options for both consumer and server hardware who want smaller and lighter products. Could open up a whole new segment in the lower, to middle tier hardware market.
 

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