SOtM Launches sMB-Q370 Motherboard

1 hour ago, MarcelNL said:

what I read until now it seems as if the PCI bus has it's own clock...YMMV....I'll wait for the more informed response from Jord....

Just found it out myself…

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Modern procesors rely on a 100MHz base clock (BCLK) which is generated by a phase locked loop (PLL) circuit inside the chipset or platform controller hub (PCH).

Different components in the CPU die can thus get their clock speeds using that BCLK and a multiplier/ratio. For example, a 3GHz core will use a 30x multi while the integrated GPU running at 1.1GHz will use a 11x multi and a DDR4 memory controller running at 2400MHz will use 24x.

Intel's current SoC clock layout with the init CLK (BCLK) which is generated by the PCH. Note that most components operate on separate clock domains.

Older computers used a crystal oscillator to generate the front-side bus (FSB) clock which was then used to get the final clock speed. A 486 with an FSB of 25MHz for example, could use a 2x multi to achieve 50MHz.

https://www.quora.com/What-is-used-to-create-clock-rate-for-processors-If-it-s-a-crystal-how-can-it-be-so-high-rate/answer/Yowan-Rajcoomar?ch=15&oid=134717785&share=5a39998b&target_type=answer

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So therefore, even if you have an add-in PCIE cards that are CPU direct it is worth adding an external clock to the motherboards system chipset because it controls the CPU frequency.  So my earlier understanding was wrong.

The Q370 chipset in the SOtM can intrinsically do ethernet, but they decided to use a dedicated chipset for ethernet and provide for its own clock input… so it must be doing something better than what the integrated chipset in the Q370 can achieve.

At least we can now summarise that if you have a Solarflare card, JCAT NET XE or similar that it’s only the external clock on the chipset that’s worth bothering with.

All of this stuff should be obvious, but it’s not easy to find.

This starts me thinking about the chipset - gaming motherboards are therefore likely to sound better because the chipset has to be better at timing the CPU under higher frequencies.

New theory:  Chipsets such as Intel c621 are also intended to do a lot more functions, PCI lanes, etc… It’s this need to manage increased complexity which means that the chipset designer has to improve clocks on the chipset to manage all of these different operations compared to a consumer level chipset.  Therefore, the more complex (advanced) the chipset the better it may sound when undertaking simple tasks such as audio playback.  This is Taikos approach.  SOtM approach is to inject a higher quality clock into a consumer grade chipset and other tweaks.

This is an interesting theory - we’ll never know which approach to chipset clocks is better though because each platform uses different CPU’s (which sound different), memory etc… no way to compare, we can only judge at a macro level.

10 hours ago, Gavin1977 said:

Back on topic:

 

The sMB-Q370 appears to accept two external clocks - 24Mhz and 25MHz.  Can anyone shed light on the following:

• Can external clock be added to both, or just one of these at at time?
• What motherboard functions do these two clock frequencies control?

Reason for my question is that if 24Mhz clock on the sMB-Q370 if for the onboard USB clocks, but you have a standalone USB card with a good clocks, then you could obviously look to try upgrading the 25MHz clock first.  In other words, there may be a preferable upgrade path in terms of money spend.

 

Equally if the clocks just affect the Intel Q370 chipset, then then may be no benefit for those out us who use PCI cards which are 'CPU direct' and avoid the chipset entirely.

 

Thanks

Most of the latest motherboard chipsets from Intel or AMD use 24MHz for system operation and 25MHz for Ethernet connection. These frequencies are not specifically selected clock frequencies for use in the sMB-Q370. In the basic specification of the sMB-Q370, two clocks operate separately, which may cause mutual interference. However, when sCLK-EX is installed, the sMB-Q370 operates in synchronization with the master clock, mutual interference between clocks can be eliminated. This means that the generation of clock noise and interference on the board is almost eliminated. In addition, if a high-precision master clock of 10 MHz such as rubidium or OCXO is used, the timing accuracy is dramatically improved and jitter is greatly reduced, so you can hear the sound quality improvement.

On 5/15/2022 at 3:51 AM, Gavin1977 said:

sMB q370. - so which lanes are CPU direct, and which ones go through the system chipset?

 

PCI-E 3.0 x16 slot
PCI-E Gen.3 x4 slot
PCI-E Gen.3 x1 slot
2x M.2 M key 2280 (PCI-E x4)
2x M.2 E key 2230 (PCI-E x2, USB)

 

 

Pcie x 16 goes cpu direct and the others are connected to the system chipset.

@MayfromSOtMHave you considered bifurcating the cpu direct x16 lanes to smaller ones ? x16 is pretty much a waste of bandwidth for any audio addon cards. The max needed would be a x4.

7 minutes ago, MayfromSOtM said:

Obviously there will be users who want the PC for playing audio plus "video" as well..  

 

And you can use the tX-USBexp to x16.

And there are so many audio elements to consider other than what you think of the PCIe bus. I can't explain everything .

 

Anyway, using the usb port with pcie x16 will help certainly sound quality, but the improvement in other parts would be bigger than that.

 

I bet you will be able to experience the difference in sound quality from other motherboard immediately once use the sMB-370, please try it.

Well there are also reports that sometimes PCIe cards attached to the system chipset can sound better, so it’s not always the case that CPU direct is best.  However, CPU direct is probably the more consistent & recognised approach to good sound.

We’re all keen to try sMB-370 - just waiting for a review.

I'm testing the sMB-Q370 + SCLK-EX with 10MHz (75 Ohms) input.

It has arrived :~)