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<TITLE>RE: [LinuxBIOS] LNXI Merge: lnxi-patch-14/16</TITLE>
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<P><FONT SIZE=2>>Are io-apics limited to apic ids 0x0-0x0f as well?<BR>
><BR>
>My memory says to me the limit should be 0x0-0xff...<BR>
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before enable ext_apic_id, Opteron only can use 4 bit for apic id, So only 16 apic id.<BR>
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After enable ext_apic_id in every opteron, it will use 8 bit for apic id, So we got 256 apic id.<BR>
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Then CPU can use 0x10 above apic id.<BR>
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some io apic device only support 4 bit apic id, So We can leave 0x0-0xf to them.<BR>
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that is for AMD, it is said that intel's from p4 has 256 for default.<BR>
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I cut and paste something for you from Kernel list.<BR>
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> - 1: 82489DX -- communication using a five-wire inter-APIC bus, 8-bit<BR>
> physical ID, 32-bit logical ID, etc.,<BR>
><BR>
> - 2: Pentium-style -- communication using a three-wire inter-APIC bus,<BR>
> 4-bit physical ID, 8-bit logical ID, etc.,<BR>
><BR>
> - 3: P4-style -- communication using the system bus, 8-bit physical ID,<BR>
> 8-bit logical ID, etc.<BR>
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>According to what AMD told us, all K8 CPUs support 8-bit APIC IDs<BR>
>("extended APIC IDs" in their speak), but they are only enabled<BR>
>"when both ApicExtId and ApicExtBrdCst in the HyperTransport Transaction<BR>
>Control Register are set".<BR>
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YH<BR>
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