JMicron

From Wikipedia, the free encyclopedia
Jump to: navigation, search
JMicron Technology Corporation
智微科技
Industry Computer
Headquarters Hsinchu, Taiwan
Products Chipsets
Website www.jmicron.com

JMicron Technology Corporation (Chinese: 智微科技; pinyin: Zhìwēi Kējì) is a Taiwanese manufacturer of integrated circuits which mostly produces Serial ATA and related controller chips.[1]

Its chips are used by a number of companies, such as ASUS,[2] Gigabyte, and MSI[3] in PC motherboards, though because of difficulties, newer MSI models have moved to using integrated Marvell controllers.[4]

SSD Controllers[edit]

JMicron's JMF601 and JMF602 SATA flash controllers were reported to have issues with write latency, causing a stuttering problem.[5][6] The performance problem was attributed to the small buffer size used in the controller.[7] Some manufacturers tried to get around the problem by using 2 JMicron controllers and added more cache, but this increased the cost and still failed to deliver the improved performance.[8] In June 2008, JMicron released version B of the affected controllers, which claimed to improve write latency and allow reserving more spare blocks to overcome the issue,[9] but Anandtech's test showed that although JMF602B has twice the cache of the JMF602A controller and has less stutter, 4KB random write has 74x the latency and under 2% write speed of Western Digital VelociRaptor 300GB.[10]

JMicron's SSD controller is widely adopted by many SSD manufacturers such ASUS Eee PC, Corsair,[11] OCZ, and Transcend. JMicron was the first[citation needed] company to provide an SSD controller chip to these companies, allowing them to produce reasonably priced MLC SSDs. JMicron was to announce a new SSD controller with a DRAM cache in Q3 2009,[9] but no such announcement occurred.

JMF602 would be succeeded by JMF612.[12]

Linux Compatibility[edit]

JMicron SATA/IDE controllers are often incompatible with some boot loaders. In particular, those using GRUB, such as Ubuntu, cannot boot in some conditions (2006/08, 2.6.17).[13] The 2.6.18 Linux kernel and JMicron controller BIOS 1.06.53[14] solved these incompatibilities, but may not be present in existing products, or may require re-flashing the motherboard BIOS. Other bootloaders such as the Windows NTLDR boot loader and EXTLINUX work fine. It has been fixed by the latest distros.

Security breach[edit]

According to the comprehensive analysis of Stuxnet virus released by Symantec in 2011,[15] a JMicron digital certificate for Windows got compromised, allowing attacker to digitally sign malicious drivers, then revoked by Verisign : "The attackers would have needed to obtain the digital certificates from someone who may have physically entered the premises of the two companies [Realtek and JMicron] and stole them, as the two companies are in close physical proximity." states the report.

Products[edit]

JMicron makes products for a number of different applications, including:

  • PATA-SATA translation Bridge
  • USB-ATA bridge
  • 1394+USB-SATA bridge
  • PCI-Express-ATA bridge
  • PCI Express-1394 bridge
  • SATA Port Multiplier/Selector with RAID
  • PCI Express-Ethernet bridge
  • USB+SATA flash controller
  • SSD controller
  • PCI-Express flash card readers

See also[edit]

References[edit]

External links[edit]