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Bifurcated Initial Program Load Diskette

IP.com Disclosure Number: IPCOM000062474D
Original Publication Date: 1986-Nov-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Greenberg, MS: AUTHOR [+2]

Abstract

A method is described for packaging of two different types of IPLable systems on a single diskette. On the PC/RT, there are two types of Initial Program Load (IPL). The first is done via the Read Only Storage (ROS) code and uses a boot record located on physical sector 0 of the IPL media. The second is done via the Virtual Resource Manager (VRM) Machine Control Procedures (MCPs) and uses sector 0 of the minidisk or physical sector 0 of the diskette since minidisks are not supported on diskettes. The boot records for these two means of IPLing a system are not compatible. The ROS IPL code executes as a result of turning on power to the PC/RT or depressing an IPL key sequence.

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Bifurcated Initial Program Load Diskette

A method is described for packaging of two different types of IPLable systems on a single diskette. On the PC/RT, there are two types of Initial Program Load (IPL). The first is done via the Read Only Storage (ROS) code and uses a boot record located on physical sector 0 of the IPL media. The second is done via the Virtual Resource Manager (VRM) Machine Control Procedures (MCPs) and uses sector 0 of the minidisk or physical sector 0 of the diskette since minidisks are not supported on diskettes. The boot records for these two means of IPLing a system are not compatible. The ROS IPL code executes as a result of turning on power to the PC/RT or depressing an IPL key sequence. The ROS code will interrogate the diskette drive, and if the drive is ready and a diskette is inserted with a valid boot record on it, the program pointed to will be IPLed. If the VRM has been IPLed by the ROS code, it does a similar function and looks at the diskette drive for a diskette with its valid boot record and, if so, IPLs the virtual machine pointed to by the boot. The ROS code always uses the first 128 bytes of the boot record. The VRM MCP was initially designed to use the first 128 bytes. The following table shows the formats of these two records.

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In order to allow a virtual machine to exist on an ROS IPLable diskette, the MCP component design in the VRM was modified to check all 128-byte logical blocks within the boot record...