Zen 2 instead of Zen 3 in PS5

[Ivan Tuzikov]

This article : https://www.tomshardware.com/news/amd-epyc-rome-7nm-launch,40116.html
says:
zen3 design complete
and wikipedia says: ps5 powered by zen2
Why so? What are the obstacles to use zen3, since it is already complete?

 

[cdrkf]

This article : https://www.tomshardware.com/news/amd-epyc-rome-7nm-launch,40116.html
says:
zen3 design complete
and wikipedia says: ps5 powered by zen2
Why so? What are the obstacles to use zen3, since it is already complete?

There are a couple of reasons- the first and biggest one is what they mean by 'Design Complete'- that basically means they have the schematics for the processor drawn up and that the design has been proven to work under simulation. They are unlikely to have any actual physical Zen 3 processors yet. Once you get to the design complete stage, they then have to go through 'tape out'- where they start building the first actual parts on the manufacturing process. Then there will be several stages of test chips that they test / tweak to get the best out of it (these are called Engineering samples and where a lot of early leaks come from). That then may result in them needing to make updates to the design. This happened recently with AMD's 'Navi' GPU- they were set to release earlier in the year however reports were saying that the first Navi silicone had a fault so AMD had to tweak it, which delayed it by about 6 months.

Secondly you have the issue of development time- it takes at least 6 months to get a finished design into production, realistically it's more like 12 months to allow for testing. With consoles that time is even longer given that Sony / Microsoft need to supply finished systems to game developers well ahead of launch. The PS5 developer kits are already about in the wild (although these won't be the same as a final PS5 the underlying hardware has to be pretty close so launch games can be properly tested). I would say the PS5 design has been set for at quite a while already- I'm actually surprised it's using Zen 2 and not Zen + as it's likely the PS5 chip was being developed before Zen 2 was finished. At that point Zen 3 would have been underway but would still be very early.

It's also worth noting AMD have said that Zen 2 is the big performance jump, Zen 3 is likely going to be a more minor improvement (like Zen + over original Zen).

 

[boju]

Rumour floating around zen3's mc controller could be ddr5 orientated. Big change if so. Thinking zen2 processors could be the last for am4.

 

[cdrkf]

Rumour floating around zen3's mc controller could be ddr5 orientated. Big change if so. Thinking zen2 processors could be the last for am4.

I think DDR5 for Zen 3 is unlikely, and when it does come out it's almost certainly destined for the server market first.

Also keep in mind- given the way the Zen cpu's are assembled the memory support has nothing to do with the core design- that is determined by the separate IO die. That gives AMD a huge amount of flexibility as they can essentially mix and match parts (so for example they could offer a DDR5 enabled server part and use a different IO die for the desktop).

I think we'll see one more generation of CPU's on AM4 (may just be a Zen+ like refresh but I would expect tweaked parts next year one way or another).

When it comes to moving to the 'AM5' socket we could see that generation of CPU's span both sockets. AMD did this with the move from AM2+ to AM3 with Phenom II (the Phenom II 940 was a socket AM2+ cpu with DDR2 support, whilst they released the almost identical Phenom II 945 on the newer AM3 socket with DDR3 support). Given the modular design of Zen based cpu's that would be even easier to do that it was back then (with Phenom II, AMD actually included both DDR2 and DDR3 memory controllers on the CPU, which is a non issue with Zen).

 

[boju]

Youre right, apparently confirmed. Oh well was wishful thinking by the time zen3 is around 🙏 ddr5 can't come fast enough.

https://www.overclock3d.net/news/so...ir_zen_3_milan_processors_will_not_use_ddr5/1

 

[Ivan Tuzikov]

There are a couple of reasons- the first and biggest one is what they mean by 'Design Complete'- that basically means they have the schematics for the processor drawn up and that the design has been proven to work under simulation. They are unlikely to have any actual physical Zen 3 processors yet. Once you get to the design complete stage, they then have to go through 'tape out'- where they start building the first actual parts on the manufacturing process. Then there will be several stages of test chips that they test / tweak to get the best out of it (these are called Engineering samples and where a lot of early leaks come from). That then may result in them needing to make updates to the design. This happened recently with AMD's 'Navi' GPU- they were set to release earlier in the year however reports were saying that the first Navi silicone had a fault so AMD had to tweak it, which delayed it by about 6 months.

Secondly you have the issue of development time- it takes at least 6 months to get a finished design into production, realistically it's more like 12 months to allow for testing. With consoles that time is even longer given that Sony / Microsoft need to supply finished systems to game developers well ahead of launch. The PS5 developer kits are already about in the wild (although these won't be the same as a final PS5 the underlying hardware has to be pretty close so launch games can be properly tested). I would say the PS5 design has been set for at quite a while already- I'm actually surprised it's using Zen 2 and not Zen + as it's likely the PS5 chip was being developed before Zen 2 was finished. At that point Zen 3 would have been underway but would still be very early.

It's also worth noting AMD have said that Zen 2 is the big performance jump, Zen 3 is likely going to be a more minor improvement (like Zen + over original Zen).

Thank you, exhaustive explanation!