the SGPIO spec. is generally adopted and implemented in products from most major HBA and storage controller vendors such as LSI, Intel, Adaptec, Nvidia, Broadcom, Marvell Technology Group and PMC-Sierra. Most products shipping with support for SAS and SATA drives support this standard. SGPIO timeout conditions The SGPIO spec calls for the target to turn off all indicators when SClock, SLoad and SDataOut have been high for 64 ms; in practice this is not consistently followed by all vendors. Also, in some vendors' implementations the clock may be halted sporadically or stopped during or between cycles. Another — rather impractical — variation between vendors is the state in which the clock is left after a cycle. Backplane Implementations of the SGPIO bus The idea behind this specification was to be able to use low cost CPLDs or microcontrollers on a back-plane to drive LEDs; in practice, it has been found that there are variations in timing and interpretations of the bits between vendors, thus a simple CPLD would only work for a specific implementation thoroughly tested with one product from one vendor. A microcontroller is more applicable for this purpose, although the 4-bit SGPIO interface custom bus is not implemented on them - sampling of the 4-bit lines using GPIOs 100 kHz bit operations is too slow for many low-cost microcontrollers to handle whilst handling LED and other functions simultaneously. The length of the bit stream varies between HBA or storage controller; some vendors will stop the bit-stream when reaching the desired drive, while others will clock it all the way through. Some SAS-expander's bit streams may be as long as 108 (36×3) bits. The safest implementation which ensures compatibility between all HBA and storage controller vendors is to use an ASIC, specifically, a combination of a microcontroller core with a hardware SGPIO interface; this concept was patented in 2006 by AMI and implemented in a series of backplane controller chips named the MG9071, MG9072, MG9077, and MG9082. These chips will receive 1 or 2 SGPIO streams and drive LEDs accordingly; the latest chip from AMI, the MG9077, can be configured by pull-up and pull-down resistors to adopt to 16 different configurations of SGPIO buses and drive the LEDs accordingly. Since the availability of these chips from AMI, major OEMs including NEC, Hitachi, Supermicro, IBM, Sun Microsystems, and others are using them on their back-planes to receive the SGPIO streams