JMicron

JMicron Technology Corporation

Industry	Computer
Headquarters	Hsinchu, Taiwan
Products	Chipsets
Website	www.jmicron.com

JMicron Technology Corporation(Chinese: 智微科技) 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

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

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

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

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

References

External links

• JMicron official website

v t e Solid-state drives Key terminology Encryption ECC Flash file system Flash memory SLC/MLC Flash memory controller Garbage collection IOPS MB/s Over-provisioning Secure erase Trim command Wear leveling Write amplification Flash manufacturers Intel Micron Samsung SK hynix Toshiba Controllers Independent JMicron Marvell Phison SandForce Captive Fusion-io Indilinx Intel Samsung sTec SSD manufacturers List of solid-state drive manufacturers Interfaces Serial ATA (SATA) SATA Express SAS FC USB PCI Express (PCIe) NVM Express (NVMe) Configurations HDD form factors mSATA M.2 PCI Express expansion card Related organizations INCITS JEDEC/JC-64.8 ONFI NVMHCI USB-IF SATA-IO SFF Committee SNIA SSSI T10/SCSI T11/FC T13/ATA Category