WingNews logo WingNews
top | item 34261608

(no title)

castratikron | 3 years ago

I'm hoping someday there will be an embedded Linux processor with this much cache. 128MB on-die SRAM means the PCB would no longer need separate DRAM. The complexity of the board routing would also go down. That much RAM ought to be enough for a lot of embedded applications.

discuss

order

LeifCarrotson|3 years ago

The economics don't work out. Why would you avoid something as trivial as board routing, as cheap as $2 per gigabyte DRAM, and as performance-enhancing as having gigabytes of main memory, just to use a 128 MB on-die (or on-package) SRAM (at a price of ~$500/GB?)?

The main distinction between application processors that can run Linux and microcontrollers that use onboard RAM (and often Flash) is that the former have an MMU. It's attractive to imagine that your SBC might only need something as simple as a DIP-packaged Atmega for an Arduino, and I can imagine a system-on-module - actually, saying that, I think several exist, ex. this i.MX6 device with a 148-pin quad-flat "SOM" with 512 MB of DDR3L and 512 MB of Flash:

https://www.seeedstudio.com/NPi-i-MX6ULL-Dev-Board-Industria...

Whether you consider that Seeed branded metallic QFP (which obviously contains discrete DRAM, Flash, and an iMX6) to be a single package, while a comparably-sized piece of FR4 with a BGA package for each of the application processor, DRAM, and Flash on mezzanine or Compute-module style SODIMM edge connectors would not satisfy your desire for an embedded Linux processor with less routing complexity, I don't know. They build SOMs for people who don't want to pay for 8 layers and BGA fanout all the time.

I don't think there are enough applications for embedded systems that need 128M of onboard SRAM that won't support the power budget, size, complexity, and cost of a few GB of DRAM.

ilyt|3 years ago

> The economics don't work out. Why would you avoid something as trivial as board routing, as cheap as $2 per gigabyte DRAM, and as performance-enhancing as having gigabytes of main memory, just to use a 128 MB on-die (or on-package) SRAM (at a price of ~$500/GB?)?

Size? But then vendor could just ship the CPU+RAM stacked on top of eachother.

redox99|3 years ago

That would be incredibly inefficient. The price difference of such a 128MB L3 + 0GB DRAM, compared to let's say 128MB L3 + 2GB DRAM would be quite small, and in practice the performance would be much much higher because realistically in your 128+0 setup you'll be wasting easily half of that on the OS or libraries data that isn't actually needed at the moment, whereas having DRAM you can actually use the whole 128MB of L3 for things that need to be fast.

It's also extremely niche to have a workload that requires such high CPU performance, but that it would fit including a linux OS in 128MB. Usually something like that is FPGA or DSP territory.

I think what you want is a cheap ARM CPU with DRAM stacked on top of it on the same package (which exists).

rektide|3 years ago

If you just want to reduce board complexity (what a hobbyost/maker/homebuilder dream that would be), there's lots of package-on-package and system-in-package offerings already!

AllWinner V3s, S3. Theres a SAMA5D2 SiP. Bouffalo BL808 (featured on the Pine Ox64). There's a lot a lot more. I think there's a couple with even more memory too.

Intel's Lakefield, with Foveros stacking, was an amazing chip with 1+4 cores and on chip ram. High speed too, 4266MHz, back in 2020 when that was pretty fast. This is more for MID/ultrabooks, but wow what a chip, just epic: add power and away you go. Ok not really but not dealing with routing (and procuring!) highspeed ram is very nice.

Intels been doing such a good pushing interesting nice things in embedded, but the adoption has been not great. The Quark chips, powering the awesome Edison module, had nice oomph & Edison was so well integrated, such an easy to use & so featureful small Linux system... wifi & bt well well well before RPi.

It would be fun to see DRAM-less computers but I more imagined them being big systems with a couple GB of sram. There's definitely potential for low end too though!

packetlost|3 years ago

The Pine64 Ox64 has a Bouffalo Labs BL808 with 64MB of pSRAM for $6-8 and an MMU. It's already got sorta-working Linux build for it.

sylware|3 years ago

I want to build my DYO usb keyboard, that including 64bits RISC-V assembly coding of the keyboard firmware.

I have been lurking on the Ox64 for while but I need a few more green lights:

- Is the boot rom enough to fully init the SOC? Aka, I don't need to run extra code I would need to include in my keyboard firmware on the sdcard.

- The hardware programming manual misses the USB2 controller with its DMA programming. Even with some SDK example, you would need the hardware programming manual to understand properly how all that works.

- I want to run my keyboard firmware directly from the sdcard slot, and that directly on the 64bits risc-v core, possible? (no 32bits risc-v core).

rowanG077|3 years ago

Note that PSRAM is just a DRAM with an easier interface. It's not at all comparable to true SRAM.

castratikron|3 years ago

Now that's what I'm talking about. Very cool, thank you.

daemin|3 years ago

Might be worth taking a look at the announced Intel Xeon MAX chips then. I watched a video on it last night and these new server CPUs have a boatload of memory on the chip and can actually run without needing external DRAM.

sylware|3 years ago

On a "3nm" process, how much die real estate for 8GB/16GB of sram presuming we are in a fantasy world with massive dies?

sroussey|3 years ago

No change. SRAM got almost no process improvements compared to 5nm. And 5nm had minimal compared to 7nm. So 3nm has “3nm”-class small transistors and 7nm class SRAM.