Gopal Miglani, August 27, 2023

Selecting Flash Memory for ZapperBox DVR

TV showing the ZapperBox channel guide.

There are three types of Flash memory:
1. Multi-Level Cell or MLC.
2. Single-Level Cell or SLC
3. MLC used as SLC or pSLC

Each type offers different features, lifespan and cost tradeoffs.

Source: Unipi Technology. https://www.unipi.technology/key_feature/what-are-the-differences-between-memory-card-types-and-why-is-it-important-to-know-them-371

pSLC is a combination of MLC and SLC technologies. It is MLC Flash whose memory cells emulate the SLC architecture by using only two outer logic states. That gives them up to five times the lifespan of MLC cards at the cost of reduced memory capacity while reducing the cost by up to 50% compared to SLC cards.

In MLC Flash, each memory cell can have more logic states as it can contain two or more data bits. As a result, MLC cards can offer significantly higher memory capacity for a lower price. On the other hand, memory blocks are sensitive to memory cell wear, resulting in a lifespan of around 3000 rewrites. After the expiration of this lifespan, it is strongly recommended to replace the card with a new one.

Table header 0SLCpSLCMLC
Number of rewrites50k-100k10k-30k3k-10k
Write speed400 μs400-500 μs1,400 μs
PriceHighestModerateLower

It is advisable to only use SLC Flash memory for data applications like recording video. SLC Flash is typically sold under brand names like “Pro Endurance” by Samsung. See https://a.co/d/h1WrkW9. This microSD card claims to offer 140,150 hours of recording or about 16 years of life. However, the data rate for such recordings is not specified.

Another example is the SanDisk Extreme Pro. See https://a.co/d/8NhJTtU. This microSD card does not specify its total write lifespan. The ZapperBox “Storage” menu under “Settings” will offer an option to turn off the pause/play buffer starting with v2.2. This is advisable for Flash memory that is not designed for at least 100k rewrites.