MIPS Technologies Porting Android 4.1 to MIPS Architecture

angry tapir writes with news on Android getting support for a third architecture. From the article: "ARM rival MIPS is continuing its push to make a mark in low-cost tablets and quickly trying to bring Android 4.1 (Jellybean) to its processors. 'We are working aggressively on bringing Jelly Bean to MIPS, and expect that it will be available to our licensees very soon,' said Jen Bernier-Santarini, director of corporation communications at MIPS, in an email. Tablets with MIPS processors are largely low-cost and have found buyers mostly in developing countries. MIPS last week said a new tablet called Miumiu W1 from Chinese company Ramos would become available in a few months in India, Latin America and Europe. The tablet has a 7-inch screen, a MIPS processor running at 1GHz, front camera and a microSD slot for expandable storage."

Comments

Fragmentation

[Dan East]

Great. Now we'll see the same fragmentation Windows CE had all those years. Most games use the NDK and contain binary compiled specifically for ARM. Obviously those apps will not run on the MIPS processor. Microsoft eventually learned this was not a good thing and finally forced all OEMs to use ARM to qualify for Pocket PC branding.

Now all we need is Android running on SH3 and we'll have gone full circle.

Re:Fragmentation

[Tapewolf]

Great. Now we'll see the same fragmentation Windows CE had all those years. Most games use the NDK and contain binary compiled specifically for ARM. Obviously those apps will not run on the MIPS processor.

The NDK now has MIPS support out of the box. Going forward it would probably be a good idea to compile for all supported targets.

Re:Fragmentation

[TheRaven64]

Also, if conditional prefixes were so great, why's ARM64 eliminating them.

ARMv8 is not eliminating them, it's reducing the number of instructions that have them. Conditional instructions are useful because you can eliminate branches and so keep the pipeline full. For example, consider this contrived example:

if (a < b)
a++;

On ARMv7 and earlier, this would be a conditional add. The pipeline would always be full, the add would always be executed, but the result would only be retired if the condition is true. On MIPS, it would be a branch (complete with the insanity known as branch delay slots, which if you look at the diassembly of most MIPS code typically means with a nop, so you get to waste some i-cache as well) and if it's mispredicted then you get a pipeline stall.

On ARMv8, you don't have a conditional add, but you do have a conditional register-register move and you have twice as many registers. The compiler would still issue the add instruction and then would do a conditional move to put it in the result register. From the compiler perspective, this means that you can lower PHI nodes from your SSA representation directly to conditional moves in a lot of cases.

Basically, 32-bit ARM is designed for assembly writers, ARMv8 is designed for compilers. As a compiler writer, it's hands-down the best ISA I've worked with, although I would prefer to write assembly by hand for ARMv7. I wouldn't want to do either with MIPS, although I currently am working on MIPS-based CPU with some extra extensions.

Re:In case you're wondering

[fuzzyfuzzyfungus]

To what degree are 'ARM manufacturers' reasonably a monopoly? The rise of ARM devices whose performance people give a fuck about does seem to have opened room for whoever is currently selling the hottest part on the street to charge a nontrivial premium; but cut back a bit from the bleeding edge and it's a veritable knife-fight of utterly undistinguished and cheap offerings.