New tool for Intel/Linux systems monitors power use on a per-process basis. This is excellent, as a few months ago I decided I wanted to have a tool like this, and this saves me from writing it!
There is also a new NO_HZ feature in the latest Linux kernel 2.6-21 that stops the clock when the CPU is idle. PowerTop can be used to see how much power that saves.
Friday, May 18, 2007
Thursday, May 17, 2007
microSD and microSDHC Storage for Millicomputers
Its been a while since I last posted here, mostly due to my change in employer, as mentioned on my personal blog... Now that is settled, I have a backlog of things to discuss here. Also, I'll be at the Techshop pavillion at Maker Faire this Saturday and Sunday afternoons.
There is an interesting price graph for 2GByte microSD at Nextag. It shows an introduction at about $120 last September, trending down to about $25 now. Amazon has it for $25 and Amazon Marketplace for $16.50. Meanwhile, larger devices are shipping using the microSDHC format at 4GByte, and announcements have been made for 8GByte. The microSD format gives a performance of around 20MBytes/s, so for 2KB reads that works out at a maximum of 10,000 random reads/second. Writing at 6MB/s works out at a maximum of 3000 random 2KB writes/s. Even allowing for operating system overhead, several thousand IOPS should be possible at under ten cents per IO per second and $10/GByte.
Of course, most millicomputer CPUs interface directly to devices like microSD, so there is no support device or interface needed. Just a microSD carrier or two, per millicomputer module.
There is an interesting price graph for 2GByte microSD at Nextag. It shows an introduction at about $120 last September, trending down to about $25 now. Amazon has it for $25 and Amazon Marketplace for $16.50. Meanwhile, larger devices are shipping using the microSDHC format at 4GByte, and announcements have been made for 8GByte. The microSD format gives a performance of around 20MBytes/s, so for 2KB reads that works out at a maximum of 10,000 random reads/second. Writing at 6MB/s works out at a maximum of 3000 random 2KB writes/s. Even allowing for operating system overhead, several thousand IOPS should be possible at under ten cents per IO per second and $10/GByte.
Of course, most millicomputer CPUs interface directly to devices like microSD, so there is no support device or interface needed. Just a microSD carrier or two, per millicomputer module.
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