Why did Sony use internal adapters for some of the stuff in PlayStation 4?

[jza]

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I watched the Fail0verflow talk about the system design of Sony PlayStation 4.

In the talk they mention that the PS4 has an internal SATA hard disk attached to a SATA-USB adapter, which is then connected to the USB host controller of the system. This is done despite the system having native SATA support.

Additionally, Sony has chosen to not use the HDMI output of the chipset, but instead has internally wired the DisplayPort output to a Panasonic DisplayPort-HDMI adapter chip, of which HDMI output is used as the actual HDMI output of the system.

At first, these design choices look ridiculous, but then again, there must have been some good technological reasons to do them, especially when the adapter chips increase the production cost of the system.

What could have those reasons been?

[ataradov]

I bet it is a result of late changes in the architecture because something did not work. In a grand scheme of things those chips add like $3 to the BOM. Sometimes it is more expensive to re-engineer things, especially for a piece of gear that will be replaced in 2-3 years.

[Kjelt]

Not sure, I agree it looks like a weird design choice.
A possible reason for switching the HDMI output could be the HDCP requirements from the 4k UHD consortium. These HDMI+HDCP specs change every year or so, a project of this size runs for three years.

[xani]

I bet it is a result of late changes in the architecture because something did not work. In a grand scheme of things those chips add like $3 to the BOM. Sometimes it is more expensive to re-engineer things, especially for a piece of gear that will be replaced in 2-3 years.

Sure but it was for a design that was sure to sell tens of millions during that time. I'd bet time constraint more than saving money.

For SATA-to-USB maybe they just didn't have time to write driver ? I'd imagine ATI only had one at hand for Linux, not BSD they based PS4 on

[TheUnnamedNewbie]

Regarding the Sata thing - I don't know a bunch about SATA protocols and controllers, but is it possible that they wanted to avoid some form of congestion with the blueray player and wanted to dedicate all SATA resources to getting data off the blueray as fast as possible/with as low latency as possible?

In addition, the guy giving the talk is doing a great job in being the stereotypical security know-it-all jerk that thinks he knows better than everyone else. (just listen to the part around the 28 minute mark).

I doubt the guys doing the design were stupid, and there will likely be very good reasons for doing these things. Perhaps the spec changed or they wanted to do something that wasn't possible with the built-in HDMI port, and because of that switched over to an external HDMI decoder? I don't know. The guy giving the talk clearly thinks he knows everything though, since he says it's stupid.

[SiliconWizard]

A possible reason for switching the HDMI output could be the HDCP requirements from the 4k UHD consortium. These HDMI+HDCP specs change every year or so, a project of this size runs for three years.

Sounds quite possible indeed. The HDMI output capabilities of the chipset probably didn't meet the final requirements. I don't know if the guy has studied the differences between the PS4 and PS4 pro. That could be interesting. Those choices may have something to do with having a common architecture between the two platforms.

[xani]

Regarding the Sata thing - I don't know a bunch about SATA protocols and controllers, but is it possible that they wanted to avoid some form of congestion with the blueray player and wanted to dedicate all SATA resources to getting data off the blueray as fast as possible/with as low latency as possible?

VERY unlikely.

First, SATA is point to point so 2 devices on 2 SATA channels do not impair eachother. So unless you do something silly like only one physical SATA channel + port extender, it doesn't matter

Second, you want to optimize HDD speed, not bluray (and bluray is way slower than limits of either SATA or USB). Why ? Downloaded games play from hard drive, and even some physical ones also require install to hard drive.

In addition, the guy giving the talk is doing a great job in being the stereotypical security know-it-all jerk that thinks he knows better than everyone else. (just listen to the part around the 28 minute mark).

I doubt the guys doing the design were stupid, and there will likely be very good reasons for doing these things. Perhaps the spec changed or they wanted to do something that wasn't possible with the built-in HDMI port, and because of that switched over to an external HDMI decoder? I don't know. The guy giving the talk clearly thinks he knows everything though, since he says it's stupid.

Sure, but sometimes the reason is just "it works, and it is good enough". There is a plenty of designs that are technically just plain bad,  just because of constraints.

Also you should NEVER discount the possibility of stupid. Especially given a track record of some of Sony's departments...