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HyperTransport Passthru Card Detection Disclosure Number: IPCOM000021185D
Original Publication Date: 2003-Dec-31
Included in the Prior Art Database: 2003-Dec-31
Document File: 5 page(s) / 158K

Publishing Venue



This invention solves the problem of detecting a Passthru card when inserted into a CPU socket. BIOS will need to know if there is a CPU present or a Passthru card present to properly set up the HyperTransport interfaces of the remaining CPU's. There are no known solutions to this problem.

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HyperTransport Passthru Card Detection


     A 4-way system can be detected by its' Presence_Det pin. The VID lines for the installed CPUs will be strapped appropriately for the core voltage used. For example, if the VID encoding for each of the CPUs is 0x01100, then this would set the core voltage to 1.25V as per standard practice for VRM design. Using this VID encoding and Presence_Det pin, BIOS will be able to detect a CPU or Passthru card.


     When a Passthru card is inserted, BIOS will monitor the Presence_Det pin and VID[4:0], which will be encoded 0x11111. A value of 0x11111 will disable the VRM. With the signals monitored, a Presence_Det plus VID encoding (0x11111) will signify the presence of a Passthru card and BIOS can configure the HyperTransport links of CPU1 and CPU2 appropriately.

Figure 1: 4-way System


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Figure 2: 3-way System

BIOS Code Function

     BIOS will start detection with the boot processor (CPU0). BIOS will monitor Presence_Det0 pin and VID[4:0] lines for CPU0. If there is no Presence_Det0, then BIOS will flag a configuration error. With a valid Presence_Det0, if the VID read is 0x11111, then BIOS will flag a configuration error as well. A value other than 0x11111 will configure the HyperTransport links of CPU0 appropriately. Next, Presence_Det1 pin and VID[4:0] lines for CPU1 will be monitored. If there is no Presence_Det1, then detection is complete. With this config...