Raspberry PI 2 or Compute module

     The Pi foundation is very prone to misinformation because of a cloudy crystal ball. Before the Pi 2 release I see http://www.makeuseof.com/tag/raspberry-pi-featureinterview/ which shows Eden not worried about competiton in 2013 after ramping up production.  As late as April 2014, Eben was claiming no need for a Model C because of software incompatible problems for the current Model B/B+. But then in February 2014 with the RPi 2 he admits maybe being wrong and back tracks his original comments with https://medium.com/@Xataka/raspberry-pi-present-and-future-of-the-minicomputer-revolutionizing-the-sector-6aa711252cb6.

This shows a different view with with Linux being open, but M$ coming in with the Windows 10 IoT core. Interesting!

C

Jumping in late: My understanding is that the Compute Module happened because people said they wanted to use RasPi in actual products but didn't want to mess with the nasty original Model A/B form factor with connectors on all four sides.  Plus they wanted more GPIOs than the original Model A/B, and something that used less power.

So to satisfy all these requirements in the most flexible way, you get the Compute Module.  Unfortunately, a modular design is always more expensive than a single-board design: you have more connectors and more PC boards.  Sure, you can snap things together like Lego, but Lego is expensive too.

I suspect that once people saw the price, the demand evaporated and they either kludged the existing board or did a fully-custom design with a different SoC.

The other thing that happened is that the B+ came out a couple months after the Compute Module.  The B+ added GPIOs and replaced the inefficient LDO voltage regulators with switchers.  So RasPi itself eliminated two of the reasons for the Compute Module.

Update:  The Model A+ was another nail in the Compute Module coffin.  If you can get by with 256MB DRAM, the Model A+ gets you a RasPi with single USB for US$20.  You can then plug in your own USB expansion board designed for your product and/or pop on a custom HAT.

JMO/YMMV

"I wrote meaning the exact opposite. Then replica is wrong anyway because it is considered a replica a copy (identical) by the same creator."

Check out the definition of clone, it means an exact copy. The term replica is rarely used in electronics. Actually the PCB does not have to be an exact copy as long as the schematics, and connector layouts are.

"The first is why you insists focusing the attention that the like-PI are not the PI, I told the same, and this is what I usually see on a lot of cases, last but not least the case of the Chipkit that aims to put itself beside Arduino with something more. No matter if they reach the goal or not."

Your the one who brought up clones, not me. I just pointed out that there are no clones (exact schematic copies) of the Pi. Almost all of my replies are about the Pi, with a few references to other Pi like hardware (my entire reply to Michael is about the Pi, nothing else)

as needed to respond to your posts.

"The second is why you insiste about the DIMM form factor, this is an appreciable solution (maybe the only one). Then my initial thinking was to verify with the other users if there was really something incredibly better as I read in this alternative model or this is - for a series of aspects - the worst "model" of the PI series. If I have to decide, I'll adopt the PI2 without hexitation, it is sure. also in a project that is commercial."

No idea what you mean here. The Pi compute module is in a DIMM form factor so that you can plug it in to the hardware support you designed for the product you want to produce. The expansion board is only supposed to be used for

hardware (support) and software development of this product, it is not meant to be used in a commercial product.

There is clearly a language barrier here.

Gary Stewart wrote:

 

Check out the definition of clone, it means an exact copy. The term replica is rarely used in electronics. Actually the PCB does not have to be an exact copy as long as the schematics, and connector layouts are.

In electronics, a clone can mean something that is functionally identical, even if not an exact copy.  Here's definition #2 from Wiktionary: "A copy or imitation of something already existing, especially when designed to simulate it."

For example, a "PC clone" is a computer that's functionally identical to an IBM PC.  It's able to run the same software, the external interfaces are the same (though they may be placed differently), and you can use the same add-on cards.  It does not have to use the same chips, e.g., it can use an AMD CPU in place of an Intel CPU as long as they both run PC software.  The clone may have better or worse CPU performance.

John, no matter; maybe there is a confusion between the target of this discussion and a language disquisition. Amen

Yes I am well aware of that. However as I am sure you are well aware of, you can not make a functionally identical (hardware and software) clone to a Raspberry Pi without using Broadcom SoCs

(or a functionally identical SoC which does not exist) since most of the "PC" functionality, unlike the first couple of generations of PCs and their clones, resides inside the System on a Chip.

Back to the original post.

This is how compute modules (and the expansion board) are expected to be used:

1) Pi compute modules by themselves are useless.

2) To make the compute module useful you must design a board that connects the I/O pins on the compute module (from the BCM2835 SoC) to whatever other circuits or

    connectors you need for your product. Eventually you will plug compute modules into the boards you designed and ship them as as part of that product.

3) To help you design the hardware for that board (and the software that runs on the compute module) the expansion board provides connections to the I/O you need to

    build and test the circuits that your product will use before you commit them to the board that you design to plug the compute modules in to.

4) You keep the expansion board and at least one compute module and use them to help design another product for another day.

Note that compute modules are only really useful if you need I/O from the BCM2835 SoC for your product that is not already accessible on the regular Pi's expansion

or other connectors or more I/O than what is already accessible on the Pi's expansion or other connectors. Other issues such as power consumption or availability

(if very large quantities are needed) may favor the compute module/product board. If neither of the conditions are met or if the other issues are not important then the

compute module does not offer any advantages at all and is in fact at a serious disadvantage to the Pi 2 so just use a regular Pi (A+, B, B+) or Pi 2.

So Gary, as bit sadly I should admit, the good ways of the compute module are locked, to use it as a bare alternative to the PI is probably (sure for me) sensless and is also worst than the PI 2, The good option to have the "DIMM" element only (the core) seems so far away in the future that maybe never arrive ...

This is also the reason that also in cases where some experimental applications have developed Pi clouds they have used the only possible way, the original Raspberry PI

Enrico

IMO, the RPi 2 is so much more advanced there is no reason to go back to old versions of the hardware.  Unfortunately, the compute module is based on the old hardware.

If space is an issue and you need several of the RPi in a single location, I have to question of the RPi is the correct solution.  I mean if you have 4 or 5 of them you might as well just use a real computer that is going to have much more capability than a dozen compute modules.  I think I if you need a couple compute modules in a small area that may be the way to go.  But anymore is just getting wasteful.

If you need all the GPIO, there are ATMegas with tons of GPIO and use a fraction of the power.  Heck, the Ardunio mega has over 2 times the GPIO as a single compute module.  If all you need is GPIO, having a full fledged OS and everything to go with it is waste IMO.

Joey,

there is a slight difference between Arduino with NO O.S. (it's a micro controller) and the SBC like the PI (or Gizmo2 or many other) that has an O.S.

Then, if you have a project that for some reasons you need MORE than one RPI, this means that you need more than one computer, with its own boot, its own operating system and so on. That is you use a "big computer" with tons of GPIO, you need anyway - for the same application - use more than one. That needs a room instead of a case.

Enrico

"there is a slight difference between Arduino with NO O.S"

Please explain, I was thinking power differences.  Not to mention full OS takes much more room and Ram so external chips are needed for ram and storage.  Amtel's chips is all internal except minor things like clock etc..

What is an example where you need  more than 1 computer with own boot etc..?