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AMD's Ryzen 9 9950X3D2 Dual Edition crams 208MB of cache into a single chip

arstechnica.com

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Re: AMD's Ryzen 9 9950X3D2 Dual Edition crams 208MB of cache into a single chip

#161

Post by hxorr »

WD-42 wrote: post #116
2001zhaozhao wrote: post #69

Earlier quoted context omitted.

Yeah the only way to run 4 sticks of DDR5 decently is with Intel. It's a bit of a shame that you can't cram enough RAM to run big models. The most I could get running on 10GB VRAM + 96GB RAM was a REAP'd + quantized version of MiniMax-M2.5

I’m running 128gb on a 9550x now with 4x32gb sticks and it’s terrible. It’s unstsable, post time is about 2 minutes (not exaggerating)and I’m stuck at a lower speed. I’m considering just taking 2 of the sticks out and working with 64gb and increasing my swap partition. The nvme drive is fast at least. This is my first time off intel and I have to say I don’t understand the hype.

What ddr5 speed are you running? 6000 is technically an over clock, AMD only guarantees being able to run at something like 4800 or 5200.

You may need to bump up voltages slightly for your CPU's IMC (I needed to on my ryzen 8700F to run 6000 stable). Its CPU sample dependant.

Also as other commenter pointed out, typically 4 sticks will achieve lower stable clocks

Re: AMD's Ryzen 9 9950X3D2 Dual Edition crams 208MB of cache into a single chip

#162

Post by mort96 »

noir_lord wrote: post #146
mort96 wrote: post #125

Earlier quoted context omitted.

Got it running with 4800MT/s and literally 30 minute boot times in an AM5 machine. The 30 minute boot time could be worked around by enabling the (off-by-default) memory context restore option in BIOS, but it really made me think something was broken and it wasn't until I found other people talking about 30 minute boot times that I stopped debugging and just let it sit for an eternity. It's so bad. I don't get why th…

You need to enable MCR (which trains the memory once and caches the result for (iirc) 30 days) otherwise yeah, booting is horribly slow, even the 64GB I have can take several minutes but with MCR it boots basically instantly. Some motherboards have it off by default.

From my comment:

> The 30 minute boot time could be worked around by enabling the (off-by-default) memory context restore option in BIOS

Re: AMD's Ryzen 9 9950X3D2 Dual Edition crams 208MB of cache into a single chip

#163

Post by mort96 »

jazzyjackson wrote: post #157
WD-42 wrote: post #134

Earlier quoted context omitted.

It's the RAM. It needs to "trained" which takes some time but for for some reason these boards seem to randomly forget their training, requiring it to happen again.

huh, its been a decade since i built a PC, whats changed?

DDR5 is much, much more fickle than DDR4 and earlier standards. I think it's primarily due to pushing clock speeds (6000 MT/s would be insanely fast for DDR4, but kinda slow for DDR5).

Memory training has always been a thing: during boot, your PC runs tests to work out what slight changes between signals and stuff it needs to adapt to the specific requirements of your particular hardware. With DDR4 and earlier, that was really fast because the timings were so relatively loose. With DDR5, it can be really slow because the timings are so tight.

That's my best understanding of it at least.

Re: AMD's Ryzen 9 9950X3D2 Dual Edition crams 208MB of cache into a single chip

#165

Post by trynumber9 »

pwr22 wrote: post #99

I'm interested to know if the L3 cache all behaves as a single pool for any core on either CCD, whether there's a penalty in access time depending on locality or whether they are just entirely localised.

It does not. For any of the dual CCD parts AMD has ever released for consumers. Even Strix Halo which has higher bandwidth, lower latency interconnect doesn't make a single L3 across CCDs.

It'll probably only happen when they have a singular, large die filled with cache upon which both CCDs are stacked.

Run this test if you're curious: https://github.com/ChipsandCheese/MemoryLatencyTest

Re: AMD's Ryzen 9 9950X3D2 Dual Edition crams 208MB of cache into a single chip

#166

Post by roboror »

jazzyjackson wrote: post #157
WD-42 wrote: post #134

Earlier quoted context omitted.

It's the RAM. It needs to "trained" which takes some time but for for some reason these boards seem to randomly forget their training, requiring it to happen again.

huh, its been a decade since i built a PC, whats changed?

It's an AMD thing

Re: AMD's Ryzen 9 9950X3D2 Dual Edition crams 208MB of cache into a single chip

#167

Post by Retr0id »

kristianp wrote: post #164

Nobody adds L1+L2+L3 like that, because L1 stores a subset of L2 and L2 stores a subset of L3. Just say 192MB of L3.

It depends on the implementation, it is possible for a cache line to be in L1 but not L2, etc.

Re: AMD's Ryzen 9 9950X3D2 Dual Edition crams 208MB of cache into a single chip

#168

Post by RiverCrochet »

basilikum wrote: post #12
chao- wrote: post #4

Crazy to think that my first personal computer's entire storage (was 160MB IIRC?) could fit into the L3 of a single consumer CPU! It's probably not possible architecturally, but it would be amusing to see an entire early 90's OS running entirely in the CPU's cache.

KolibriOS would fit in there, even with the data in memory. You cannot load it into the cache directly, but when the cache capacity is larger than all the data you read there should be no cache eviction and the OS and all data should end up in the cache more or less entirely. In other words it should be really, really fast, which KolibriOS already is to begin with.

I thought there was an MSR buried deep somewhere that enables "Cache as RAM" mode and basically maps the cache into the memory address space or something like that.

Lol a quick Google search leads me to a Linked in post with all the gory technical details?

https://www.linkedin.com/pulse/understanding-x86-cpu-cache-m...

Re: AMD's Ryzen 9 9950X3D2 Dual Edition crams 208MB of cache into a single chip

#169

Post by abcde666777 »

A year ago I swapped out a 5800x for a 5800x3d to get more stable frame rates in Counterstrike 2. Made a sizable difference, especially to 1% lows, so these large caches can clearly be a big boon. Granted it's also obvious the game is poorly optimized, the gains look less significant for most other titles.

Re: AMD's Ryzen 9 9950X3D2 Dual Edition crams 208MB of cache into a single chip

#170

Post by ManuelKiessling »

timschmidt wrote: post #56
fakwandi_priv wrote: post #51

Earlier quoted context omitted.

AMD had an upgrade path with the 5700x3d, assuming you’re on AM4. Just reading now that they went out of production half a year ago which is a shame. I was very impressed being able to upgrade with the same motherboard 6 years down the line.

I'm the mythical customer who went from a 1700X in a B350 motherboard near launch day to a 5800X3D in the same board (after a dozen BIOS updates). Felt amazing. Like the old 486DX2 days.

Nearly same story here. AMD and MSI will forever hold a special place in my heart.
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