ESP32-S3 UnilC PSRAM support

[gesp32]

Hello Espressif team,

We have a product based on ESP32-S3-WROOM-2-N32R16V and are reviewing whether to stay on ESP-IDF v5.4.1 or move to v5.4.2+.

While reviewing the v5.4.2 release notes, I noticed this:
- PSRAM: Supported UnilC Octal PSRAM on ESP32S3 (a8e166e)

which adds UnilC as an accepted vendor ID for ESP32-S3 octal PSRAM.

To help with long-term planning, I’d appreciate clarification on:

1. Was this change motivated by UnilC PSRAM already appearing (or expected to appear) in the in-package PSRAM used by ESP32-S3-WROOM-2-N32R16V modules?

2. For ESP32-S3-WROOM-2-N32R16V, should customers assume the internal PSRAM vendor may vary across manufacturing lots over time?

3. Is ESP-IDF v5.4.2+ recommended to ensure forward compatibility with future S3 module lots, even if current lots work correctly on v5.4.1?

Thanks for any insight you can share.

[gesp32]

Bumping for visibility. I can't find information about UnilC PSRAM aside from the 5.4.2 release notes.

[michael]

Hi gesp32,

Here are the versions that support this PSRAM:

Target Branch Merged Released
release/v5.0 4d78c54 v5.0.9
release/v5.1 c5ccf3d v5.1.7 (target)
release/v5.2 857c712 v5.2.6
release/v5.3 9e58fe0 v5.3.4
release/v5.4 a8e166e v5.4.2
master 847ac1a v5.5

Please be noted that when the supply is not stable, replacing materials (flash/psram) inside the product is a way out to keep the supplying. ESP-IDF will try to provide the support ASAP. Latest versions (v5.4.2 compared to v5.4.1) will absolutely contain support of more devices (we almost never remove existing support) that may come into your devices in the future.

There are some effort and machanism to prevent such HW change influencing your production. Please contact your sales on how to get notified and assist on dealing the problem in advance.

[michael]

More comments on this topic..

As far as I know adding the PSRAM into the BOM is not a determined thing. But we always recommend the latest release on the same branch, mainly for those fixes introduced. It's not only for compatibility to future hardware.

[gesp32]

Thanks for the reply. That's about what I expected -- flexibility to support the supply chain.

I presume that since UnilC PSRAM support was added, that there is intention to use the part at some point.

We'll discuss internally and see if we can make the jump to v5.4.3 in an effort to future-proof ourselves a bit.