The Big Difference Between Power9's Industry Standard Memory vs Buffered Memory

POWER9 Memory changes and what it means.

Our last article was about the primary changes made to the POWER Systems, scale out line up with the release of the first set of POWER9 (You can view some of the POWER9 benchmarks here) servers back in February. We briefly covered several of the changes including the change made to the type of memory used for the new POWER9 systems and speculated on the reason for this change.

In this article, we will delve a little deeper and explain the differences between the two different types of memory (Buffered and 'Industry Standard'), and why the change from buffered back to industry standard is a big deal and what it means for the consumers in the small and medium business market.

Buffered Memory Vs 'Industry Standard' Memory:

To begin a short, visual primer on the differences between the two types of memory, and how they fit into servers. The slides below show the visual differences between buffered and industry standard ('IS') DIMMs as well as how they look when installed into various servers including POWER7, POWER8 and POWER9.

(READ: IBM POWER8 vs. POWER9 Comparison for 2020)

3 Basic differences: Form Factor, Cost, & Performance

At first glance the most glaring difference is the sheer size of the buffered memory as compared to IS memory, which is twice or up to four times the size of a single IS DIMM. In addition to this, the buffered cards also house a processor that gives this type of memory its name. This difference is most important for the smaller form factor, 2U servers because the full height of the larger buffered memory cannot fit into the available space. While the size difference is the most visually apparent, it is not the most significant; more important is the difference between cost and performance.

As we speculated in the previous article, the most important factor at the end of the day for most is cost and this difference is perhaps the most impressive as well. For example, a 16GB DDR4 DIMM for POWER8 (Buffered) has a list price of $1,110.00, whereas a 16GB DDR4 DIMM ('IS') for POWER9 has a list price that is ~44% lower at $619.00. That trend is true for all but the largest memory features, primarily due to various market circumstances:

POWER8 DDR4 Memory (IBM Pricing):
EM91 $1,110 16GB DDR4 Memory
EM92 $1,700  32GB DDR4 Memory
EM93 $3,440  64GB DDR4 Memory
EM94 $7,880  128GB DDR4 Memory
EM95 $15,760  256GB DDR4 Memory

POWER9 DDR4 Memory (IBM Pricing):
EM60 $409 8GB DDR4 Memory - 324D EM60 78P4191
EM62 $619 16GB DDR4 Memory - 324E EM62 78P4197
EM63 $1,179 32GB DDR4 Memory - 324F EM63 78P4198
EM64 $2,699 64GB DDR4 Memory - 325A EM64 78P4199
EM65 $9,880 128GB DDR4 Memory - 324C EM65 78P4200

Industry standard memory may have the edge in both size and pricing, but where the buffered memory shines is performance. This is, of course, by design as well; IBM strives to bring the best hardware to market and the introduction of buffered memory for the POWER8 line of servers furthers this goal. The heat sink that is visible on the buffered memory cards is attached to a processor that works to optimize the way the memory interacts with the CPU of the server. It should also be noted that, in the higher end POWER9 models, buffered memory is still in use due to its increased performance.

However, this doesn't mean industry standard memory is inadequate; after all, it's called 'Industry Standard' for a reason. The memory used for the POWER9 Scale Out systems is the same kind of memory you'll find in almost every other type of server on the market as well as in most desktops. POWER9 systems offer the exact same memory performance as its market competitors, but offers higher memory capacity in the same market.

On a side note, in the pricing lists above, that there is a difference between available memory capacities. POWER8 does has a largest available DIMM of 256GB compared to the POWER9's 128GB as well as the non-existence of an 8GB DIMM for POWER8. POWER9 servers have twice the available DIMM slots than their comparable POWER8 counterparts so there is no need for a 256GB feature to get to the system max memory for scale out systems. The 8GB feature for POWER9 was released just last month and it will be interesting to see if it becomes a popular choice for entry level systems.

In Summary:

IBM switched things up by introducing IS memory for POWER9. Moving away from the larger and more complex buffered memory, that was introduced in the previous generations, for the entry level systems means they have brought lower prices to consumers while maintaining the reputation ever increasing benchmarks for performance the POWER Systems line up is known for.