What I'm wondering is if they could be using the hypervisor to just partition the CPU, and permanently assign one of the cores to the baseband VM, and leave the rest assigned to the Android VM.
Although, the article didn't say it had an odd number of cores, so I guess not (unless it's really a tri- or penta-core SoC)
The site you mention looks veryh interesting, but they probably only give access to industry people. Is there any similar site where regular people can see reliable prices ?
Re:$34 Smartphone Part II – Teardown
by userbinator on Tuesday May 19, 2015 @10:21AM
(#9570213)
Go to "Stock Look-up" and click on "Spreadtrum".
Maybe they don't allow direct linking.
Here are prices on some Spreadtrum parts:
http://www.europe-asia-electronics.com/index.php?op=stocksea....
The SR1019A is $0.564, SC2330B is $0.876, and SC6825C is $3.83. I found the VC5282 on a different site for 2.30RMB ($0.37 USD), and prices for KMN9X000RM seem to vary a lot but vary between $0.14 (possibly a scam) and $15.
It's hard to estimate the BOM cost because of all the other pieces' unknown specs, but I don't think it's more than ~$20.
When the phone is assembled you can trigger it by holding ‘Volume Down’ while the phone is off, and simultaneously plugging it into USB. I haven’t tried ‘ResearchDownload’ yet, unfortunately it sounds like it can only write images not read them – taking a backup involves flashing a working CWM for the phone model first.
That's the same method used on Mediatek smartphones; they have the bootloader in ROM too, and this is also what is used to load initial firmware on blank devices at the factory. (It's also how to recover from a "hard brick".) The ResearchDownload utility looks like a clone of Mediatek's SpFlashTool, and if the bootloader mode works in a similar fashion, dumping the full eMMC should also be possible like it is in MTK. All the bootloader does is provide commands to write data into memory and execute it.
I'd be very surprised if they were actually virtualising the baseband and applications processors on the same CPU, since the former needs hard realtime constraints. The MTK SoCs use a separate Cortex-R4 core for each modem (two in the case of dual-SIM) to do this. They could be using vLM to emulate a "virtual" SoC, allowing them to change the underlying hardware while still running the same Linux kernel. The possibility that they're virtualising Mediatek's Linux kernel on their hardware is not so far-fetched...