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Forum Index : Microcontroller and PC projects : WeAct 16 MB PSRAM, 16MB Flash Wifi

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Gerad
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Joined: 10/01/2024
Location: Germany
Posts: 86

Posted: 10:12am 16 Oct 2026

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Does WeAct work with WebMite 7.XX.XX and 16 MB of PSRAM?
YES.

terekgabor
Senior Member

Joined: 02/01/2026
Location: Hungary
Posts: 150

Posted: 10:45am 16 Oct 2026

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Hello!
Which WeAct do you mean?

G@bor

matherp
Guru

Joined: 11/12/2012
Location: United Kingdom
Posts: 12007

Posted: 11:05am 16 Oct 2026

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A 16 MB part would not work as the code stands. The size is detected and the reserve placed correctly, but the heap's page map is fixed at 6 MB, and the allocator would write past it on the very first allocation.

Detection and the reserve scale with the chip. The ID decode in psram.c only knows 2, 4 and 8 MB (AP Memory) and 1, 2, 4 MB (ISSI), but it is followed by a wrap probe that doubles from 1 MB up to the 16 MB QMI window and takes what it measures, so a 16 MB part comes out as 16 MB. PSRAM_RESERVE (2 MB, 2.5 MB on the PC3) is taken off the top of that measured size, in PicoMite.c for the heap and in psram.c for the slot init, and everything inside the reserve sits at fixed offsets: the 384 KB context area, the RAM slots, the stream in the remainder. None of it grows. Only the heap would, to 14 MB.

The page map does not scale. Memory.h:76 fixes PSRAMHEAPMAX at 6 MB, so psmap is 1536 words. SBitsSet indexes it by offset divided by 256 and 16 with no bound, and every allocator scans downward from the top of the heap, so on a 16 MB part the first allocation sets bits at word 3583 of a 1536-word array, 8 KB into whatever BSS follows.

I will modify the code in the next release so that it is treated as an 8Mb part so that it won't cause memory corruption
Edited 2026-10-16 21:48 by matherp

Gerad
Regular Member

Joined: 10/01/2024
Location: Germany
Posts: 86

Posted: 12:02pm 16 Oct 2026

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@Peter
The Raspberry Pi Pico SDK, starting with version 2.3.0/2.3.1, supports the RP2350B and external PSRAM of up to 16 MB. Just one question: Do you plan to make the memory fully available for “Webmite”?

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matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 12007

Posted: 12:27pm 16 Oct 2026

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Probably not, needs quite a big change and these chips are super expensive for no obvious benefit for most users.

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