News AMD B550 Motherboards Should Still Be Easy on Wallets

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Titan
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Many 300-series and even more 400-series boards could handle PCIe 4.0 from the CPU perfectly fine until AMD decided to push microcode to disable it. There is effectively no reason for B550 boards to be any more expensive than B450 models other than the chipset cost and any additional improvements motherboard manufacturers may add on top. I'd like to see some real 6+2 phases VRM options.
 

alextheblue

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Many 300-series and even more 400-series boards could handle PCIe 4.0 from the CPU perfectly fine until AMD decided to push microcode to disable it. There is effectively no reason for B550 boards to be any more expensive than B450 models other than the chipset cost and any additional improvements motherboard manufacturers may add on top. I'd like to see some real 6+2 phases VRM options.
From what I remember reading, there were concerns over real-world signal integrity in many boards that OEMs enabled 4.0 on. So AMD put the brakes on it, rather than risk having problems dumped in their lap. Of course no third parties tested speeds and error rates as compared to an X570 so who knows how widespread the issues were (or were not).

As far as VRM options go, I'd like to see them go even higher and undercut the entry-level X570 boards by $10-20, while matching in power delivery. But I admit it's not very likely. Side note, stock of decent AM4 motherboards seems to be getting slim, at least at last month's pricing. I hope supply loosens up soon.
 

InvalidError

Titan
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As far as VRM options go, I'd like to see them go even higher and undercut the entry-level X570 boards by $10-20, while matching in power delivery.
You already got that: the lowest-end X-series motherboards have the same fat (double-FET) 4+2 phases commonly found on A/B-series motherboards, real 6+2 would be an improvement for those too. Some boards already have doubled-up drivers and chokes too. In those cases, the only real added cost is ~$1 for the controller upgrade a good chunk of which canceled out from removing 1/4 of the doubled quad.
 

alextheblue

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You already got that: the lowest-end X-series motherboards have the same fat (double-FET) 4+2 phases commonly found on A/B-series motherboards, real 6+2 would be an improvement for those too. Some boards already have doubled-up drivers and chokes too. In those cases, the only real added cost is ~$1 for the controller upgrade a good chunk of which canceled out from removing 1/4 of the doubled quad.
You're saying a native 6+2 would deliver more power than an equivalent doubled 4 + 2?
 

InvalidError

Titan
Moderator
You're saying a native 6+2 would deliver more power than an equivalent doubled 4 + 2?
One major problem with doubling FETs is that they will practically never be perfectly matched in on-resistance, temperature, switching speed, etc. and all of these increase losses. If each switching pair has its own inductor, cross-conduction losses can be reduced but the current mismatch between the two phase halves will increase and at this point, you practically have all the components necessary for 8+2 apart from the VRM controller.

A good 6+2 design can easily beat a crappy 4+2. It isn't only about power, a real 6+2 would have less ripple and faster transient response too, which means less power likely to be required to maintain stability. You may only have six transistor pairs instead of eight, but current will be more evenly matched across all of them. Each choke will have 1/6th of the current passing through them instead of 1/4 (non-doubled chokes), which will reduce choke losses by ~50%. Also, you can take the budget from cutting 25% of the fat-quad's FETs on better FETs and support circuitry for the remaining six pairs, more efficiency gains there.

There are quite a few benefits to going real-6 over fat-4. The only downsides I can think of is $1 extra for the controller and two extra $0.10 chokes. I'm not a fan of overkill VRMs but fat-4 is getting old even for the entry-level, wouldn't mind paying $3 extra for real-6 on B550.
 
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nervousstate

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Many 300-series and even more 400-series boards could handle PCIe 4.0 from the CPU perfectly fine until AMD decided to push microcode to disable it. There is effectively no reason for B550 boards to be any more expensive than B450 models other than the chipset cost and any additional improvements motherboard manufacturers may add on top. I'd like to see some real 6+2 phases VRM options.
The PCB quality of B450 board was not high enough to meet the SNR Requirements of the PCIe 4.0 - Increase the PCB quality is a cost so that's reason one. Also B450 Boards have been on the market for a long time, so the cost of production was calculated in a Pre-COVID19 world and have simply been in inventory for the most part. Supply chain cost has increased and thus resulting product cost will increase. Also there is an initial release price and a price after 3 years of shelf life
 

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