POST Debugging Tool Storing Check-Point Code History
Original Publication Date: 2001-Dec-02
Included in the Prior Art Database: 2003-Jun-20
Disclosed is a device for supporting a debug by storing history of checkpoint codes as well as showing checkpoint code simultaneously. When you develop brand-new PCs, you need 2 weeks and 5 engineers for bring-up, because H/W is not mature, and you cannot check the debugging status by LCD/CRT monitor due to unconfigured video chip. Therefore, normally, POST codes have checkpoint codes at every top position of every POST rotine as described Fig.1. The checkpoint code will be written to a certain I/O(normally to a printer port 3BCh)Then, you can get to know when a system has stopped during a boot-up, by checking those I/O access cycles through printer port. However, there are two problems. One is not to support Legacy free PCs that don't have printer ports, and the other is not to get to know where the checkpoint code comes from after hung-up. For example, if a system is hung-up showing checkpoint 4Dh, you cannot tell whether this comes from 25h or 27h as you can see in Fig.1. I/O write 0x25 ………..…….. …………….... I/O write 0x26 ………..……..