this post was submitted on 07 Nov 2023
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Single Board Computers
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Yeah most are sub 1MB but e.g. STM32h7 (ARM Cortex M7) has 1MB ram. So maybe that's a good upper limit. I am a bit behind the times so maybe there's something miceocontroller-ish with more ram out there idk.
The "Biggest" uC I'm aware of are NXP's i.MX RT devices. Basically: NXP is making i.MX Crossover Microprocessors (aka: the smallest microprocessor), and i.MX RT crossover microcontrollers (aka: the largest microcontrollers). So yeah, that "RT" means they're still microcontrollers, but way bigger than normal.
https://www.nxp.com/products/processors-and-microcontrollers/arm-microcontrollers/i-mx-rt-crossover-mcus:IMX-RT-SERIES
Today, it looks like the biggest i.MX RT is a 5MB SRAM microcontroller. Which is... bigger than I expected.
Oh wow. I hadn't heard of those. Thanks. Really curious now.
I dunno, I think the i.MX RT500 are completely absurd.
0.40mm pitch BGA, okay so we're looking at an expensive PCB anyway. Like, what the hell? You need like 3mil trace / 2.5mil space to even breakout.
You can get an MPU with full scale Linux in the $5 / chip + $2 Power-management IC + $4 DDR2 128MB + $4 NAND 1GB Flash at roughly the same price, with easier to solder 0.80mm pitch BGAs.
The i.MX RT500 is expensive at $30 Qty1 and $20 in larger-scale bulk quantities.
So I'm not entirely sure what the hell the point of i.MX RT500 is. The NXP Microprocessors are literally cheaper... even after buying RAM and Flash. I mean, someone wanted it, so I recognize that its been created for someone. But... its difficult for me to imagine how or why.
I've never seen anything I'd call an MCU that has more than 2MB of SRAM (though a lot of them have the ability to address external buses for Flash and SRAM both semi-transparently, so there may be some dev boards that give more).
In case you missed the sibling comment: I just found the iMX RT500, a 249-pin BGA 'Microcontroller" with 5MB of SRAM.
https://www.nxp.com/products/processors-and-microcontrollers/arm-microcontrollers/i-mx-rt-crossover-mcus/i-mx-rt500-crossover-mcu-with-arm-cortex-m33-dsp-and-gpu-cores:i.MX-RT500
Which is absolutely the largest "microcontroller" I've ever heard of. But you're right in that 2MB is already an absurdly huge size in most cases.
Wow. At that point my reaction is ... it would be better to have an SoC. I mean I'm working with kit that typically has 64KB to 128KB of SRAM and thinking that I'm blessed with resources! 🤣
Yeah, there's entire MPU platforms that are cheaper than the iMX RT500.
And the 0.40mm and/or 0.35mm pitch BGAs just confuse me even further. (Seriously, who is getting like 2.5mil trace/space and like 6 layers PCB for a microcontroller? But cannot afford the MPUs?)
I'm guessing iMX RT500 has some power-benefits. But... it just seems absurd all together to me. But good luck on NXP on finding customers for that thing.
I think its sole use case would be for that very, very, very narrow point of intersection between "extreme power management needs" and "extreme processing requirements".
And it seems a bit quirky to make ... that ... chip for it.
But hey! At least it isn't the STM32MP1! 🤣