Application Performance Class:
The new class of performancefor applications on SD memory cards (SD 5.1)
White Paper | November 2016www.sdcard.org | ©2016 SD Association. All rights reserved

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Application Performance Class: The new class of performance for applications on SD memory cards (SD5.1)

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Executive Summary
The SD Association (SDA) released the SD 5.1 specification
to answer evolving market needs with Application
Performance Class.
Most of today’s smartphones and mobile computing
devices, Win-Mobile and Android, allow application
data to be saved on removable cards or run applications
from cards.

Product manufacturers may use the Application Performance
Class (App Performance) with its associated symbol to define acertain level of minimum performance for consumers,ensuring the SD memory card that may fit their products
allows reasonable usage for their products. This also helps
consumers choose the proper card for their product at thepoint of sale.

Google released Android Marshmallow in 2015 andexpanded microSD memory card support by offering“Adoptable Storage Devices,” which helps users to run
applications from the installed memory card.
There are some basic performance requirements based on
a combination of random and sequential memory accessthat optimize user experiences when using memory cards
as storage and/or to run applications.

Application Performance Class: The new class of performance for applications on SD memory cards (SD5.1)

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Background on Market Situations
GeneralThe SD memory card is the most popular card in the world
and is supported by a strong ecosystem. Even moresignificant, it is well-known to consumers around the worldand enjoys unprecedented interoperability and backward
compatibility.
The main use of SD memory cards until recently was for
personal multimedia content storage for photos, videos,music, etc. With that legacy usage model, performance wasdriven mainly by either fast upload/download of content orassured video or burst-shooting images. Over time, the SDA
evolved the SD specification with a focus on sequential
performance and the related defined speed classes,
including the recently introduced Video Speed Class.

In short,• It’s not just about slow content-saving any more
• It’s about application-running and new associatedperformance capabilities• A combination of higher random + sequential
performance is required
The SDA initiated new SD specification improvements tomeet market requirements by:• Standardizing a common language for consumers andproduct manufacturers, allowing best utilization ofspecific products with related best cost-effective card type
• Continually improving SD memory card protocol,
enabling higher random and sequential performance.

In parallel to the legacy needs, new requirements driven by
the mobile and mobile computing markets evolved. In thelast few years a new usage model of storing applications
and application data on removable cards emerged.
Therefore, removable cards are now used as memory
expansion of the internal embedded memory supplied
within the mobile devices in a way that its usage model
becomes somewhat similar to that of the embedded
memory, or at least for application usage. This means that
there is an increased need for SD memory cards to match
embedded storage capabilities.

Application Performance Class: The new class of performance for applications on SD memory cards (SD5.1)

5www.sdcard.org | ©2016 SD Association. All rights reservedAndroid Marshmallow introduces
Adoptable Storage Devices
Google released Android Marshmallow in October 2015 andadded microSD support as Adoptable Storage Devices,
allowing users to run applications from their device’s installedmicroSD memory card.
Android Marshmallow, and newer versions, run a benchmark
test on the microSD memory card during its adoption process.
The memory card’s performance is tested against the internal
embedded storage performance and, if the card’s performance

Solution: Application Performance Class
The Application Performance Class standard defines:• App Performance symbol for use on cards, packaging
and manuals• Assured combination of minimum random + sustained
Sequential performance levels under specified conditions
The SD 5.1 Physical specification introduced the first andmost basic App Performance level, which sets the absolute
minimum requirement bar named A1 or App Performance
Class 1. Higher App Performance Class levels will be
introduced to meet market needs.

is found to be performing at less than 25 percent of theembedded memory, a pop-up message tells the user that thecard appears to be slow.

App Performance Class 1 (A1) memory cards

This is a very positive initiative by Android and opens the door

App Performance Class A1 SD memory cards shall meetthe performance measures as given in Table 1.

for real memory expansion of mobile devices while assuringsatisfactory user experience for a given card.
However, two real-life problems appeared:• Consumers do not have a means to determine which cardthey should purchase at the point of sale, and running thebenchmark post-purchase is too late; it could cause
product returns and customer dissatisfaction.
• For many currently available cards in the market, users
may get a slow card warning message after running thebenchmark.

RD IOPS*WR IOPS

Sequential

1500

500

10MB/sTable 1 Application Performance Class 1 (A1)
*Input-Output access Per Second (IOPS) Minimums

Note that the given performance levels are assured under
the conditions defined in SD Physical Spec v5.1. Any SD
memory card that introduces itself as an A1 card (by thelogo and in the internal SD Card Status register) shall meetthe defined spec requirements. Please refer to the SD 5.1
Spec for further details.
Figure 1 shows the new App Performance symbols in both
short and long forms.

A common language between device and card manufacturers
will guide consumers to the correct card for their device andimprove satisfaction for both groups.

Figure 1 App Performance Symbol

Application Performance Class: The new class of performance for applications on SD memory cards (SD5.1)

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What is expected from product manufacturers?
Product manufacturers that support SD memory cards andIMPORTANT: The performance level that SD memory cards

need certain minimum random and sequential

are tested against allows A1 SD memory cards to pass, but

performance levels that can be satisfied by App

they cannot be guaranteed by Google. The reason is that

Performance Class 1 minimum levels may include A1 SD

the Android benchmark test is dependent on the device

memory card recommendations in manuals and productenvironment (i.e. clock speed, background apps, etc.), notpackaging to help customers choose the best SD memory

only the memory card. Therefore, the SDA highly

card for that device.

recommends the product manufacturers first test their

Manufacturers that recommend usage of App Performance
Class SD memory cards should check for the desired
Application Performance Class level as follows:
1. Check the Application Performance Class type of theSD memory card in the SD Card Status and confirm
whether it matches its requirement level.
2. In addition, or in cases where the Application
Performance Class is not indicated by the card, thehost may perform an internal benchmark test andcheck for the absolute execution time to qualify thememory card. If it matches or exceeds the execution
time expected from the corresponding Application
Performance Class expected by the host, the cardshould be accepted for use.

devices with A1 SD memory cards using the new Androidbenchmark mentioned above before they recommend
their customers use A1 cards.
Note that in any case SD memory cards that indicate
Application Performance Class support shall meet the SD
standard specification for Application Performance Class
conditions as defined in SD Physical Spec v5.1.

Test Equipment
There are several approved test equipment options in themarket that implement the SD Specification Test guidelines
and are used for self-compliance tests of SD memory cards
and host devices.

In November 2016, Google updated its benchmark test anduploaded it to the Android Open Source Program (AOSP)
for review. Per the new update, which is expected to beincluded in the pending platform release, Google relaxed
the benchmark to be a static threshold value instead of

The App Performance Class tester, for both host side andcard emulator, is expected to be ready by leading test
equipment manufacturers soon after the SD 5.1
Specification is introduced.

comparing it against the relative speed of internal storage.
The updated version, anticipated in a forthcoming periodic
update for Android Nougat, does not test the removablecard against the embedded performance. It tests it against
a fixed level (as recommended in Item 2 above).

Application Performance Class: The new class of performance for applications on SD memory cards (SD5.1)

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Summary
With the expanded usage of SD memory cards for storing applications and application data,
there is a growing need for a combination of Random and Sequential performance levels.
This demand becomes even stronger with the introduction of Android’s Adopted Storage
Device capability. The Application Performance Class was introduced by SD 5.1 Physicalspecification with the first App Performance Class, A1, to address these new market
demands. The new class assures minimum performance under given conditions and the newApp Performance symbol enables a new method of communication in the SD memory card
market, giving manufacturers a method to communicate device requirements and allowing
their customers the means of choosing the right card for their device at the point of sale.

Application Performance Class: The new class of performance for applications on SD memory cards (SD5.1)

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