4 ms·

Too bad the rp2040 doesn't have an external RAM interface. Would make for an excellent single chip, instant booting computer experience.

mordae 4y ago
It would be cool, especially with a larger package with more pins.
alexisread 4y ago
Have a look at the BL808 chip, on the sipeed M1s board. (https://www.aliexpress.com/item/1005004970779483.html https://www.aliexpress.com/item/1005004970779483.html) I've never seen an MCU with access to 64mb RAM - makes for a great target chip for a simple computer. (https://btashton.github.io/bl808-notes/soc/memory_layout.html https://btashton.github.io/bl808-notes/soc/memory_layout.htm...) There are 5 processors on the chip, which you can optionally use as required: NPU (neural processing unit https://github.com/sipeed/TinyMaix/blob/main/benchmark.md https://github.com/sipeed/TinyMaix/blob/main/benchmark.md) H264 video codec RV64 application processor capable of running linux RV32 radio processor for the 3 radio protocols it supports - wifi/BT/zigbee RV32E low power core to manage the chip The radio and application cores should run fast enough to be able to bitbang digital video signals, there is 32K VRAM which I guess might be used for the bundled touchscreen display.
lnsru 4y ago
There are countless chips for more dollars with external RAM. RAM IP costs literally dollars, costs silicon area, increases package price, makes pcb design more difficult and would probably canibalize Raspberry Pi Zero sales.
guenthert 4y ago
You mean with parallel address and data bus? That would be a whole lot of pins and quite a large effort to implement, not to speak of getting the timing right, when going beyond a clock rate of 10MHz or so. In the MCU world (quad) SPI RAM is favored, if external RAM is needed. That can be done with the RP2040 (well, you'd have to move the content yourself, there is no hardware support to transparently access external RAM, like in some other MCUs). But what exactly do you have in mind with the 'instant booting computer experience'? The RP2040 has 264KiB of RAM already (more than the address space of a PDP-11), so surely that qualifies as 'computer'. That should be enough to even emulate a 8 bit Home Computer (well, it has been done for 6502 and Z80 CPUs and whole CP/M machines and ZX Spectrum). Not that I get this obsession with 'instant on'. My chromebook is ready for me the moment (well, within a blink of an eye) I open the lid. My desktop needs a minute or so, but I reboot it only when there's a kernel update ...

mordae 4y ago

It would be cool, especially with a larger package with more pins.

alexisread 4y ago

Have a look at the BL808 chip, on the sipeed M1s board. (https://www.aliexpress.com/item/1005004970779483.html https://www.aliexpress.com/item/1005004970779483.html) I've never seen an MCU with access to 64mb RAM - makes for a great target chip for a simple computer. (https://btashton.github.io/bl808-notes/soc/memory_layout.html https://btashton.github.io/bl808-notes/soc/memory_layout.htm...) There are 5 processors on the chip, which you can optionally use as required: NPU (neural processing unit https://github.com/sipeed/TinyMaix/blob/main/benchmark.md https://github.com/sipeed/TinyMaix/blob/main/benchmark.md) H264 video codec RV64 application processor capable of running linux RV32 radio processor for the 3 radio protocols it supports - wifi/BT/zigbee RV32E low power core to manage the chip The radio and application cores should run fast enough to be able to bitbang digital video signals, there is 32K VRAM which I guess might be used for the bundled touchscreen display.

lnsru 4y ago

There are countless chips for more dollars with external RAM. RAM IP costs literally dollars, costs silicon area, increases package price, makes pcb design more difficult and would probably canibalize Raspberry Pi Zero sales.

guenthert 4y ago

You mean with parallel address and data bus? That would be a whole lot of pins and quite a large effort to implement, not to speak of getting the timing right, when going beyond a clock rate of 10MHz or so. In the MCU world (quad) SPI RAM is favored, if external RAM is needed. That can be done with the RP2040 (well, you'd have to move the content yourself, there is no hardware support to transparently access external RAM, like in some other MCUs). But what exactly do you have in mind with the 'instant booting computer experience'? The RP2040 has 264KiB of RAM already (more than the address space of a PDP-11), so surely that qualifies as 'computer'. That should be enough to even emulate a 8 bit Home Computer (well, it has been done for 6502 and Z80 CPUs and whole CP/M machines and ZX Spectrum). Not that I get this obsession with 'instant on'. My chromebook is ready for me the moment (well, within a blink of an eye) I open the lid. My desktop needs a minute or so, but I reboot it only when there's a kernel update ...