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Comment by Rohansi | Hacker News Reader

The RP2350 (Pico 2) supports external PSRAM so you can add several MB more there if you need it.

Default specs matter a lot for worldwide availability and affordability, as well as for the willingness of people to spend a lot of time creating free software for it.

520KB of SRAM is actually on the high end for microcontrollers. It doesn't seem like much but SRAM is on-die and significantly lower density than DRAM. For comparison, it's the same type of memory used for CPU caches, which are also small!

You can easily find dev boards with 8MB of PSRAM online if you need it. Or you can buy the PSRAM and hook it up yourself. If you still need more memory than that then you're looking at the wrong chip for the job.

I shouldn’t wish for more onboard RAM for the next Pico iteration because other boards already have more. Okay, dude.

Other boards with the same MCU as the Pico, yes. The only downside is you lose one GPIO.

I have always wondered kind of bandwidth you could make by multiple channels of PSRAM driven by PIO/DMA. Individually they're not so speedy(although the APS6408L-OCH-BA seems pretty crazy) , but how many can you run simultaneously. In terms of the RP2350 it would be fascinating to see how many times a second could you replace the entire contents of SRAM.

Can surely get more bandwidth but the it's less useful because it will not be directly accessible by the CPU anymore.

PSRAM is a possibility that I have explored for offloading the delay line buffers, which occupy quite a significant chunk of SRAM at the moment. It should be fast enough.

I believe PSRAM is directly accessible by CPU (there is even cache for PSRAM). Or am I missing something?

Lerc was referring to driving multiple PSRAM chips from a single Pico with PIO/DMA. The CPU will only work with a single PSRAM chip.

Yes, I was thinking of it more like bank switching.

Although, going back to the start of the thread where the suggestion was adding more RAM to future chips perhaps the request could be for support for multiple channels in the future.

It;s the age old question of parallel Vs serial Vs multi channel serial.

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