Automatic Retry of Slot On Command by Hot Plug Controller for Highly Capacitive PCI Adapters
Original Publication Date: 2002-Feb-26
Included in the Prior Art Database: 2003-Jun-20
Some IBM systems have issues with power faulted adapters causing PERR# and NMI errors when the system is powered up causing a system reboot ref: CMVC defect 159585). The problem is caused by a slow response of the power controller module (i.e. HIP1011D) indicating an OC fault to the hot plug controller ASIC. If a quicker fault response was designed into the hot plug circuit, this problem could be fixed but another issue could arise; higher power cards may not be supported in the system due to their relatively high DV/DT. I.E. they would trip the OC protection circuit. Adapters installed on the system PCI bus should be powered up as soon as possible by using the quickest DV/DT the hot plug design can support without the OC circuitry within the power controller being tripped (falsely) by the current transient when the cards power up. The hot plug circuit may power up low power adapters with a setting in the (the hot plug circuitry) design which causes the voltage ramp to the adapter to be very fast. The problem is with high power adapter cards which have lots of load capacitance, the current rush could trip the internal circuit breaker of the power control module causing it to shut down. The start up current ramp through the FET switches must be minimized so the inrush current at start up is relatively small as the adapters’ bulk capacitors charge to the V+ supply rails. Most if not all of the popular voltage control modules have some method to vary the parameters needed to control the above situations. However, these parameters are usually fixed at the time of the design and cannot be changed without rework to the hot plug controller hardware. During the design phase, care must be taken not to make the components which control the current ramp too large or else the voltage controller may not be able to adequately protect the bus or the FET switches. This invention will make two of those features automatically configurable so the hot plug ASIC will automatically retry a slot power on command to any slot which fails to power up due to a “transient” fault condition.