Thinking of making a custom AM4 motherboard

pavel

Caliper Novice
Original poster
Sep 1, 2018
32
16
Hi guys,

For quite some time I was thinking making a custom TR4 mobo for a workstation leasing business. Other boards out there are big overkills in my opinion. Other than the north bridge itself, things like sound card, PCIE/SATA expansions, WiFI, additional USB hubs, tons of "management" chips and such.

Lately the performance of regular AM4 Ryzens got so high that I though of dropping the idea of using TR4 altogether. AM4 CPUs are near completely autonomous, requiring only SPI flash to store BIOS and memory to boot. Not only I get cheaper CPUs, but lots of board space and power to spare. If I can go below $1k per system, I can think of a consumer market too, which is great money wise.

Since we talk about PCIE 4.0 now, we can carry bandwidth of PCIE 2.0 16x with only 4 lanes. That is enough for a gaming grade GPU, and a lot of other things. Moreover, we can now use SFF8643 connectors and existing cables for riser boards.

Since I can make the board work without so many extra chips now, I'm starting to think of putting a DC-DC PSU on board. Near all chips other than memory and CPU these days are fine with either 3.3V or 1.8V. And PCIE whith GPU external power takes 12V. This looks to me quite doable. I think of external voltage of 48V and every other power rail being powered by direct 48-to-x bucks, or with 48-to-12-to-n for 3.3 and 1.8 for ease of sourcing parts.

Now back to high frequency lanes. PCIE and DDR4. Those would be the only high speed lanes on the board, and that's a great thing for the cost. Since DDR4 can pack a lot on a single DIMM, and Ryzen will not get any extra perf from more than 2 DIMMs, I think of only having 2 slots. The small premium for high capacity DIMMs should worth it. For PCIE, I think of going away with regular PCIE slots as such, as most use cases will use risers anyways. 3rd gen Ryzen has more than enough lanes available to be used without chipset. I'm thinking of simply wiring all lanes to SFF8643 connectors other than ones needed for on board network and m.2 slots. In general, having less peripherals should make for easier routing, and hopefully reduce the amount of problems with PCIE signal quality.

What do you think?
 

Windfall

Shrink Way Wielder
Nov 14, 2017
1,625
1,246
Hi guys,

For quite some time I was thinking making a custom TR4 mobo for a workstation leasing business. Other boards out there are big overkills in my opinion. Other than the north bridge itself, things like sound card, PCIE/SATA expansions, WiFI, additional USB hubs, tons of "management" chips and such.

Lately the performance of regular AM4 Ryzens got so high that I though of dropping the idea of using TR4 altogether. AM4 CPUs are near completely autonomous, requiring only SPI flash to store BIOS and memory to boot. Not only I get cheaper CPUs, but lots of board space and power to spare. If I can go below $1k per system, I can think of a consumer market too, which is great money wise.

Since we talk about PCIE 4.0 now, we can carry bandwidth of PCIE 2.0 16x with only 4 lanes. That is enough for a gaming grade GPU, and a lot of other things. Moreover, we can now use SFF8643 connectors and existing cables for riser boards.

Since I can make the board work without so many extra chips now, I'm starting to think of putting a DC-DC PSU on board. Near all chips other than memory and CPU these days are fine with either 3.3V or 1.8V. And PCIE whith GPU external power takes 12V. This looks to me quite doable. I think of external voltage of 48V and every other power rail being powered by direct 48-to-x bucks, or with 48-to-12-to-n for 3.3 and 1.8 for ease of sourcing parts.

Now back to high frequency lanes. PCIE and DDR4. Those would be the only high speed lanes on the board, and that's a great thing for the cost. Since DDR4 can pack a lot on a single DIMM, and Ryzen will not get any extra perf from more than 2 DIMMs, I think of only having 2 slots. The small premium for high capacity DIMMs should worth it. For PCIE, I think of going away with regular PCIE slots as such, as most use cases will use risers anyways. 3rd gen Ryzen has more than enough lanes available to be used without chipset. I'm thinking of simply wiring all lanes to SFF8643 connectors other than ones needed for on board network and m.2 slots. In general, having less peripherals should make for easier routing, and hopefully reduce the amount of problems with PCIE signal quality.

What do you think?
Do you have any experience with motherboard development? It's one crazy expensive process. Estimates I've read put the average ATX mobo at $30,00 USD. Even if you're doing it yourself (and wow, if you can, you've got my respect), that's working a 9-5 job for a good half a year, if you don't have a full dev team behind you. Not trying to be a downer, but I've looked into custom mobos/customizing industrial boards, and even working off an existing platform it's crazy expensive. I wish you the best of luck in your endeavor, regardless.
 

paulesko

SFF Lingo Aficionado
Jul 31, 2019
135
71
I´m already frikin out trying to make my own ac-dc unit just for fun.... a motherboard looks like a whole new level of crazyness
 

pavel

Caliper Novice
Original poster
Sep 1, 2018
32
16
Do you have any experience with motherboard development? It's one crazy expensive process. Estimates I've read put the average ATX mobo at $30,00 USD. Even if you're doing it yourself (and wow, if you can, you've got my respect), that's working a 9-5 job for a good half a year, if you don't have a full dev team behind you. Not trying to be a downer, but I've looked into custom mobos/customizing industrial boards, and even working off an existing platform it's crazy expensive. I wish you the best of luck in your endeavor, regardless.
The biggest thing I've ever developed myself was a simplest android settop box. Went through 3 prototype boards until I got everything running reliably. Usually, I only take upon microcontroller projects by myself.

I'm not against dishing out $3 to $5k on getting the board done by a professional, otherwise I wouldn't have considered running a business off it. Moreover, I was underlining above that I will push for the simplest design possible, so as to make it real without involving true x86 specialist knowledge.

My biggest concern is not whether I will be able to get it designed or not, but to how make money off it with small production runs.

The thing with electronics is that you don't even think of any economics of scale until you can talk about 10k+ units. If I will be ordering a high layer count, high performance PCB in small batches, the PCB will cost few times more per piece in comparison to an average 50k+ units run.

The question there is whether I can:
  1. Get anywhere near a point where part count reduction can compensate for cost of small volume runs
  2. Get anywhere near a point where PCB layer count, material grade, and complexity reduction can compensate for cost of small volume runs
  3. Get an interest of a serious PCB design house that deals with x86 with that amount of money.
 

Windfall

Shrink Way Wielder
Nov 14, 2017
1,625
1,246
The biggest thing I've ever developed myself was a simplest android settop box. Went through 3 prototype boards until I got everything running reliably. Usually, I only take upon microcontroller projects by myself.

I'm not against dishing out $3 to $5k on getting the board done by a professional, otherwise I wouldn't have considered running a business off it. Moreover, I was underlining above that I will push for the simplest design possible, so as to make it real without involving true x86 specialist knowledge.

My biggest concern is not whether I will be able to get it designed or not, but to how make money off it with small production runs.

The thing with electronics is that you don't even think of any economics of scale until you can talk about 10k+ units. If I will be ordering a high layer count, high performance PCB in small batches, the PCB will cost few times more per piece in comparison to an average 50k+ units run.

The question there is whether I can:
  1. Get anywhere near a point where part count reduction can compensate for cost of small volume runs
  2. Get anywhere near a point where PCB layer count, material grade, and complexity reduction can compensate for cost of small volume runs
  3. Get an interest of a serious PCB design house that deals with x86 with that amount of money.
3-5K is a little low, I think. Still, looking forward to what you do!
 

pavel

Caliper Novice
Original poster
Sep 1, 2018
32
16
3-5K is a little low, I think. Still, looking forward to what you do!
I have quite a good understanding that a complex board can go up to $100k for something with a lot of high speed signals and layers, as you need more tries to debug the board, and buyers for that stuff tend to be well moneyed (telecom, carrier grade router makers, military etc.)

That's why I'm setting a quite a stretch goal of making it with 6 or less layers and as few vias as possible. With only 2 DIMMs and PCIE to route out of high speed lanes, I think it's possible.
 
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Valantar

King of Cable Management
Jan 20, 2018
721
516
This sounds incredibly ambitious, but also pretty cool. Let us know how it progresses! A question (as it hasn't been mentioned, and I don't know how this would be done): who will be writing the BIOS/UEFI for the board, ensuring PCIe compatibility, incorporating AGESA updates, and so on?
 
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pavel

Caliper Novice
Original poster
Sep 1, 2018
32
16
This sounds incredibly ambitious, but also pretty cool. Let us know how it progresses! A question (as it hasn't been mentioned, and I don't know how this would be done): who will be writing the BIOS/UEFI for the board, ensuring PCIe compatibility, incorporating AGESA updates, and so on?
If I will go with an established x86 design shop, I will certainly ask them to do that if the have access to reference BIOS. If otherwise, in worst case I can "copypaste" it from a relatively similar board.

Bios for ZEN is said to be very simple, with the only piece of code that needs to be done individually for each board being the "link training" data for DDR4
 

Dunedan

Cable Smoosher
Sep 14, 2019
8
6
Would this be similar to the board powering the ASRock DeskMini A300 (no separate chipset, DC-DC PSU onboard and so on), but mini-ITX, with support for beefier CPU's and more exposed PCIe lanes?

I contacted a motherboard vendor a few years ago, asking if they have a motherboard with more SATA ports than usual back then in the pipeline. Their response was quite surprising: "How many boards do you want?" Based on that experience I believe it should be possible to find one of the existing motherboard manufactures willing to design and produce such a board as ODM, even if the volume is "just" a few thousand pieces. Maybe ASRock would be a good first candidate to ask, as they have the A300 design already and offer customized ODM solutions as well through ASRock Industrial Computer.
 
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Hifihedgehog

Master of Cramming
May 3, 2016
381
357
You could even PM them (@ASRock System) directly here in the forums. I am dead certain SFF.Network would be thrilled if their platform became the springboard for the world's first crowdsourced and crowdfunded SFF motherboard. Maybe even AMD would get behind this because I am know a number of folks at r/AMD who would instantly get behind a novel project like the one you describe. I, for one, would love to see you take the reins of something like this and organize a thread that aims to pull this off.
 

pavel

Caliper Novice
Original poster
Sep 1, 2018
32
16
Would this be similar to the board powering the ASRock DeskMini A300 (no separate chipset, DC-DC PSU onboard and so on), but mini-ITX, with support for beefier CPU's and more exposed PCIe lanes?
Certainly, this is where I go for the technical direction. DC-DC will have to be much beefier and with higher input voltage to support a 200W+ GPU , and there will be no independent bridge to reduce complexity and layer count. I'm even thinking to forego going beyond default 4 USB ports on ZEN, and adding an audio codec. Anybody thinking of GPU workstation for serious work, and leasing it on top of that, should have zero problem to gear up on accessories if they really need them. Though, going this way will not play as nicely for consumer market.

My thoughts are more or less settled on making the most barebone way to have Ryzen + GPU + NVME + 10GBE done, and then adding as much extra conveniences as possible without radical cost and complexity increases (adding extra PCB layers, or complicating testing)

I contacted a motherboard vendor a few years ago, asking if they have a motherboard with more SATA ports than usual back then in the pipeline. Their response was quite surprising: "How many boards do you want?" Based on that experience I believe it should be possible to find one of the existing motherboard manufactures willing to design and produce such a board as ODM, even if the volume is "just" a few thousand pieces. Maybe ASRock would be a good first candidate to ask, as they have the A300 design already and offer customized ODM solutions as well through ASRock Industrial Computer.
Very likely they already had a reference design available to which they would add minimal customisations for a quite hefty premium.

I don't think I will ever go along Asrock and co, I'm not even sure if they have an office in around Shenzhen area. I'm just a too small of a fish for them