Solved! Speculation: Zen 4 (EPYC 4 "Genoa", Ryzen 7000, etc.)

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What do you expect with Zen 4?


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Tuna-Fish

Golden Member
Mar 4, 2011
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On paper Zen 4 *does* looks weaker/simpler than Golden Cove but its unquantifiable characteristics must be excellent as it ends up with similar performance at similar clock rates. Not in every workload but when averaged out they're pretty close.
Cache latencies are notably lower. That's probably all it is.



Latency in cycles is lower for all levels of cache. That 1 cycle of L1 latency probably has a deceptively high impact. L1 has >95% hit rate on most well behaved loads, one extra cycle on every access adds up.

Zen 4s reorder buffer performs surprisingly well compared to GLC despite the size difference
When your average latencies are lower, you don't need as big of a ROB to keep the units occupied.

separate integer and FP resources. approximately 0 workloads stress both at the same time , you know how like SPEC has separate FP and INT benchmarks.
That's not really right. Even heavy vector loads typically have a bunch of scalar integer "bookkeeping", like loop counters, list indexes, etc stuff they need to update.

Granted, with the 2 dedicated scalar ports, GLC now probably has enough for most cases.
 
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eek2121

Platinum Member
Aug 2, 2005
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They will probably reveal pricing once the KS part drops.

Target audience you mean? Yeah I suppose.
7000 non-X, 7600X/7700X budget builds, upcoming APUs etc

But I doubt you can't run a 7950X on them if you really wanted to.
Indeed, these boards will very likely be able to run all chips. Expect IO to be gimped, however. Likely no PCIE 5. Limited PCIE 4, if any.
 
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itsmydamnation

Platinum Member
Feb 6, 2011
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That's not really right. Even heavy vector loads typically have a bunch of scalar integer "bookkeeping", like loop counters, list indexes, etc stuff they need to update.

Granted, with the 2 dedicated scalar ports, GLC now probably has enough for most cases.
Thats why I used the word stressed . its not that there isn't a bunch of flow control , loop counter etc going on. If this was really such a big advantage AMD would have much higher dispatch then they do :) . Does anyone know if Zen3/4 has higher retirement /cycle then dispatch like Zen2 did ?
 

Abwx

Diamond Member
Apr 2, 2011
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All links must be accompanied by your own commentary.
Thats why I used the word stressed . its not that there isn't a bunch of flow control , loop counter etc going on. If this was really such a big advantage AMD would have much higher dispatch then they do :) . Does anyone know if Zen3/4 has higher retirement /cycle then dispatch like Zen2 did ?
 

Abwx

Diamond Member
Apr 2, 2011
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JustViewing

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Aug 17, 2022
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1. separate integer and FP resources. approximately 0 workloads stress both at the same time , you know how like SPEC has separate FP and INT benchmarks.
Not necessarily, not all FP workload are steaming AVX. Most of the time they will be mix of both. Having said that, compilers may optimize for Intel's combined Int/FP architecture by keeping FP and code sections separately to help with scheduler. Unlike in the past, modern schedulers are very flexible with its deep out of order buffers.
 
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Mopetar

Diamond Member
Jan 31, 2011
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Now that we're starting to see cheaper Zen 4 CPUs, I think we're going to see less expensive motherboards. It's considerably easier to talk the person who just bought a 7950X into a premium board, but the guy who's in the market for a 7600 or a 7700 is t looking to spend nearly as much.

It's the same every time a new platform launches. Companies lead with high-end products to get higher margins out of enthusiasts that are willing to spend more than the average consumer. Over time the mainstream and low-end options trickle out, but there's not a lot of financial incentive to lead with a low-cost, low-margin product.
 
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biostud

Lifer
Feb 27, 2003
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Seems like the variation is with some boards regressing to 2:1 UCLK mode when clocked at 6000. I always manually set it to 1:1 mode.
This and some differences in memory timings, which I'm sure over time will be fixed. So nothing critical that cannot be fixed with a bios update.
 
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Asterox

Senior member
May 15, 2012
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Those AM5 motherboards need to come way down in price. Otherwise nobody will be buying AM5 CPU's.
Harness your horses, much cheaper A620 AM5 motherboards are arriving in February. :grinning: AM5 socket was launched a few months ago, not say a year ago.


If we directly compare prices, and if we compare AM5/B650 technical details=you can't expect the same price it's not realistic at all.So these are motherboards from the same Gigabyte series, and to be honest the B450 model is a bit too expensive in year 2023.


 
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biostud

Lifer
Feb 27, 2003
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When there were a difference between functionality between X and B boards I can understand why you would choose an X board. But the X670E and B650E are based on the same chip (x2 for the X670E) , it is just the number of pcie lanes, sata and USB connectors that differ. How many users really need that?
 
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Det0x

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Sep 11, 2014
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JoeRambo

Golden Member
Jun 13, 2013
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Latency in cycles is lower for all levels of cache. That 1 cycle of L1 latency probably has a deceptively high impact. L1 has >95% hit rate on most well behaved loads, one extra cycle on every access adds up.
Intel has advantages with size tho, 50% more L1 for just 1 more cycle of latency is good tradeoff. And 100% more L2 with 14 vs 16 or 17 cycles is damn good tradeoff as well.
Combined that creates a situation, when workload does not allow AMD to make use of their excellent L3, they get beaten badly by wider Intel's machinery:

5Ghz vs 5Ghz:
1673783277780.png
1673783243357.png
 
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Kaluan

Senior member
Jan 4, 2022
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Those AM5 motherboards need to come way down in price. Otherwise nobody will be buying AM5 CPU's.
Okay, this has got to be trolling by some at this point. I refuse to believe everyone muttering this has never at least glanced at DDR5 B660/760 motherboard prices. They're just as expensive if not more so than low end B650 offerings. And likely even more skimp on features.

Do people really look at 12th or 13th gen performance numbers (which are almost exclusively sporting fast/non-JEDEC DDR5) then look at a ("D4") super-basic $120 B660 boards and think "gee, I can have all that but for $50 less than those expensive B650 boards!" ?

Just looked at MSI's B760M Mortar WIFI and their B650M Mortar WIFI and the AM5 one is actually cheaper.

So I'm really bewildered about WTH people are on about.

1. ALL DDR5 MOBO OPTIONS COME WITH A PREMIUM, be it AMD or be it Intel.
2. You're not really buying "premium" 13th gen performance if you go DDR4.
3. If you're not building a Intel system based on future proofing and are aware you'll get less performance w/ DDR4 then go for it. But you should probably know AM4 is still a thing too. Often cheaper as well.

Once A620 mobos drop, I hope people can stop with that misguided talking point, AM5 may have the cheapest DDR5 boards on the market.
As far as I can tell, Intel H610 DDR5 boards don't even exist (and I doubt they reliably can run 200W+ CPUs either, but that's another subject).
 

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