Two new budget CPUs join AMD’s mature lineup of Zen 2 desktop processors, but B550 will draw a line under backwards compatibility with older CPU architectures.
Two new budget CPUs join AMD’s mature lineup of Zen 2 desktop processors, but B550 will draw a line under backwards compatibility with older CPU architectures.
Since the release of 3rd Generation Ryzen CPUs and X570 motherboards in mid-2019, AMD‘s rise in regard amongst PC enthusiasts and mainstream consumers has been nothing short of meteoric. More cores, more performance, meaningful technological innovations and feature-rich motherboards all contributed to its status as the platform to beat in the conventional DIY desktop PC space, as well allowing the red team to make inroads into the Intel-dominated OEM space. This week, after a quiet Q1 on desktop, they’re introducing new Zen 2 SKUs into their product stack and divulging more details of the B550 chipset revealed last week.
The Ryzen 3 3100 and 3300X join the 3rd Generation lineup at the bottom of AMD’s desktop CPU stack, making CPUs with the 7nm Zen 2 microarchitecture available from top to bottom. They will effectively replace the Ryzen 3 3200GE and 3400G APUs as the entry point into AMDs ecosystem on the B550 motherboard platform, and mark the end of the Zen/Zen+ architecture’s place in the product stack. This will prove to be controversial, but AMD are not doing it for trivial reasons.
The Ryzen 3 3100 and 3300X’s official launch date is today (May 7th), but shipping will lag in some regions due to ongoing coronavirus mitigations put into place to protect workers and customers. AMD anticipate that the processors should be available globally from May 21st, starting from an MSRP of $99 but with retail pricing dictated by local stock levels and demand.
Outwardly Similar, Internally Distinct – AMD’s Latest Processors
Both the Ryzen 3 3100 and 3300X are 4-core, 8-thread CPUs based on the 7nm Zen 2 architecture with 18MB of Cache and a TDP of 65W. In fact, headline specifications for the Ryzen 3 3100 and 3300X distinguish between the two chips only through the Base and Boost frequencies, where they’re separated by 200MHz and 400MHz respectively. There’s more going on under the lid however.
First, a refresher. The Zen 2 architecture as it pertains to AMD’s mainstream desktop platform calls for two key components on the CPU package. The first is the large IO Die (IOD), which handles memory, PCIe and more. The second is the Core Chiplet Die (CCD), where the CPU cores and processor cache are located. A CCD has two Core Complexes (CCXs), each of which has four CPU cores and a big chunk of L3 Cache. Twelve and sixteen core CPUs have two CCDs on the processor package, those with eight and fewer have just one CCD.
AMD are able to selectively disable individual cores and entire CCXs, and they have used this feature of the architecture to populate their current product stack with 6-core and 12-core variants. The Ryzen 5 3600 and 3600X have one core disabled per CCX, and just 12MB L3 cache available per CCX (for a total of 24MB). Unlike these two CPUs however, the 3100 and 3300X don’t share an identical CCX configuration.
The Ryzen 3 3100 incorporates two CCX’s into its design, with two cores disabled per CCX for a total of four. A total of 8MB L3 cache is utilised on each CCX to bring this chip to a 16MB total. So far, so good.
The Ryzen 3 3300X disables an entire CCX, making use of each of the four cores on the other. The cores then have access to the full 16MB L3 cache available on this CCX.
This is important because the Ryzen architecture allows for the sharing of cache data between cores and across CCXs’, i.e. a CPU in CCX1 could request data from L3 cache in CCX2 (and visa versa). However accessing data across-CCX’s is slow, or at least slower than accessing data on the same CCX. As a result the Ryzen 3 3300X will be just a little quicker than the 3100 clock-for-clock.
Combined with the clock speed frequency bump, AMD believe that this difference is meaningful enough performance-wise to justify the discrete SKUs and pricing. And of course there may be effective differences in binning, overclocking performance and dynamic clocking behaviour to underscore the point.
B550 – Finally, PCIe 4 on a Budget?
Joining AMD’s Ryzen platform lineup on June 16th will be motherboards based on the long-awaited B550 Chipset. Positioned to be more affordable than the enthusiast-class X570 designs, it will be the first mainstream chipset to integrate support for PCIe 4 and hence supplant legacy B450 and X470 designs over time. That being said, its implementation of PCIe 4 support isn’t identical to X570.
B550 appears to be based on a variant of the Promontory chipset present in B450 and X470 motherboards. Unlike X570, its chipset (which AMD dub the Fusion Controller Hub, analogous to Intel’s PCH) doesn’t support PCIe 4; instead PCIe 4 operation is limited to dGPU lanes and M.2 storage wired directly to the CPU.
This echoes the preliminary (and unofficial) PCIe 4 support offered on B450 and X470 motherboards prior to AMD’s blanket removal in a post-launch BIOS update to the older platforms. AMD justified this by saying that PCIe 4 operation hadn’t been validated on these motherboards, and they couldn’t have customers assuming full compatibility due to mixed messaging. It was, indeed, something of a storm in a teacup at the time.
Still, PCIe 4 support for discrete GPUs and ultra-fast M.2 storage are the core applications for the technology on desktop. They alone should make the motherboards worthy of consideration in new builds over B450/X470, even if these is a slight price premium. One up-side however is that the B550 chipset will have a <6W TDP, and thus not require the active cooling present (and much-criticised) on X570.
Beyond this, there are a few more tweaks implemented on B550 that make it an attractive alternative to B450. Dual Graphics (SLI/CrossFire) is now supported and the general-purpose PCIe lanes are upgraded to PCIe 3.0, but most valuable will be the transition to USB 3.2 Gen 2 support. They’re small edges, but could make sense to a very selective niche of users.
Eyes on the Future & Breaking Links with the Past.
With the launch of B550 AMD are quite explicitly breaking support for Zen and Zen+ CPUs and APUs, finally drawing to a close top to bottom socket compatibility across the Ryzen desktop present since its launch in March 2017. Four years of backwards and forwards compatibility across a major architecture change is nothing to be sniffed at, but all good things must come to an end.
AMD’s rationale is that, as a budget chipset, B550 motherboards will typically be shipped with lower capacity BIOS chips than their X570 counterparts. They therefore had a choice: support all Zen, Zen+ and Zen 2 CPU and APUs, or restrict it to drop-in support for Zen 2 and as-yet unreleased processors scheduled for the near future (i.e. Zen 3). AMD chose the latter.
As a consequence Zen+ based Ryzen 3 3200GE and 3400G APUs are not compatible with B550 motherboards by default.
At the time of release AMD will not have a socketed AM4 Zen 2 APU for desktops, making the two new entry-level CPUs and a cheap discrete GPU the only budget alternative if B550 is the motherboard of choice. Realistically, that will make assembling a budget B550-based system more expensive than some may have anticipated.
By the same token, this appears to be confirmation that Socket AM4 will be present for the next generation of Ryzen CPUs. It should also mean that the release of Zen 2 APUs is more of a question of ‘when’ rather than ‘if’.
Price and Availability
Over sixty B550 motherboards are in development ahead of the platform’s June 16th launch from major partners such as ASUS, ASROCK, MSI and GIGABYTE. If the models are indeed loosely based on B450 then they should be exceptionally mature designs, with none of the problems that sometimes plague fresh products.
Unsurprisingly, AMD haven’t broached the topic of pricing as yet. We’re still more than a month away from an official release and the market can change a great deal in that time. That being said, comparisons will immediately be made to B450 (currently available at less than £70) and X570 (models starting at around £150); day one MSRP will hopefully be closer to the former than the latter.
As noted last week, the CPUs have an MSRP of $99 for the Ryzen 3 3100 and $125 for the 3300X; check with regional retailers for pricing applicable to you as and when they reach your shores.
