BitMicro has been busy upping its SSD ante. It's announced the highest capacity SSD in its class - a 155GB 3.5in form factor fibre channel connect solid state disk, offering a sustained data rate of 70Mbit/s.

Rudy Bruce, president of BitMicro, said: "This new breed of higher density 3.5in SSDs opens up a lot more opportunities for data streaming applications such as high-definition video editing and rendering that simply have to locate larger amounts of data onto flash memory for improved performance." No general use here then.

Like virtually all SSD announcements, no pricing information is given. The recent TMS sales of a 2.5TB system to the US government had a list price of $4.7 million. That's $1,880 (£1,045) per GB - not cheap. The RamSan 320 devices involved have hard drives inside them though, so it's not a pure SSD $ per GB figure.

BitMicro has also announced a 75.7GB 2.5in ATA SSD with a sustained write speed of 28Mbit/s. This is also claimed to be the highest density SSD in its class.

Unfortunately not. M-Systems has announced a 90GB 2.5in UltraATA SSD with sustained read/write rates of 40Mbit/s. M-Systems says it's the fastest flash disk in the industry. An embedded Motorola CPU is used to deliver the performance. Previous models used IBM PowerPC CPUs. THe 90GB unit costs aproximately £22,000 - which works out at £240 per GB. The bulk of the cost comes from the bought-in flash memory - NAND units from Toshiba and Samsung.

SSDs are used for aeronautical, military and industrial applications where the mechanical unreliability of rotating hard drives is not acceptable and the operating conditions exceed HDD tolerances. They are also used in business applications where response speed is paramount and disk I/O bottlenecks not permitted.

Much smaller amounts of flash memory are used in keyfob USB devices where the price per GB is still high, compared to hard drives, but the unit cost affordable due the low capacities - typically 32MB to 1GB.