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Module Presence Detection Method without Presence bit

IP.com Disclosure Number: IPCOM000144638D
Original Publication Date: 2007-Jan-03
Included in the Prior Art Database: 2007-Jan-03
Document File: 3 page(s) / 42K

Publishing Venue

IBM

Abstract

Disclosed is the algorithm of device detection without a presence bit. There is a desire to have an expandable system of module or element detection is present in the BladeCenter* environment due to the introduction of "interposer" modules. Interposer modules allow "stacking" of current modules into one module slot. The fixed hardware in the BladeCenter is wired only to detect the presence of one module in a slot. A new, expandable method of module detection is needed to handle the new hardware combinations in the older chassis design.

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Module Presence Detection Method without Presence bit

A SLIM interposer can support two legacy switches. There are three hardware, 1 interpose and 2 legacy switches, need to be detected. However, there are only two hardware presence bits available. Current detection method cannot detect all three types of hardware. Because there are only two presence bits available for three types of hardware, two designs are proposed:
design I: presence bit on legacy switch and HSSM
design II: presence bit on SLIM and HSSM

     In the BladeCenter environment. The midplane, which is a permanent element of the hardware design, contains fixed sense pins to detect presence, but the current environment is growing in a way that combines several modules into one slot through the use of "interposer" modules. Users are now able to stack several modules into one slot. A method to detect the additional modules is desired.

     The principles for the detecting the SLIM are the same for the two designs. However, their implementation is different due to the setting of presence bits. The principles are as follow:

A SLIM is present if one of the following is true
1. the VPD type code from cache matches with the VPD type code of SLIM
2. the VPD type code from polling matches with the VPD type code of SLIM
3. the presence of legacy switch is detected

Design I: presence bit on legacy switch and HSSM.

The algorithm is illustrated with IO bay 7 and 8.

zero local SLIM present bits

If (present bits of slot 7 or 8 are set)
if (read IO bay 7 VPD successful)
if ( not HSSM nor Path-Thru Module)
set local SLIM present bits on IO bay 7/8

else if (read IO bay 8 VPD successful)
if ( not HSSM nor Path-Thru Module)
set local SLIM present bits on IO bay 7/8

else

if (poll legacy switches on IO bay 7 an...