Messages in this thread |  | | Date | Mon, 11 Dec 2000 23:39:56 -0600 | Subject | Re: Linux 2.2.18 release notes | From | Peter Samuelson <> |
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[AC] > > ... added basic support for the Pentium IV. [Android] > How is the Pentium IV more advanced than the Pentium III, other than > speed? Why would LInux care about a 1500 MHz clock or 400 MHz bus > speed? Just treat the PIV as a faster PIII.
It all sounds so simple, right? Several small things to worry about:
- CPU identification and categorization. The P4 reports itself as CPU family 15 rather than family 6 like PPro, PII and PIII. Thus, Linux code that tests for certain features by saying if(cpufamily==6) didn't notice that the P4 would work. Also there was at least one format string like sprintf(buf, "i%d86", cpufamily) which is supposed to print "i686" but on the P4 would print "i1586"....
- metrics -- L1 cacheline size is the important one: you align array elements to this size when you want a per-cpu array, so that multiple CPUs do not share a cacheline for accessing their "own" structure. Proper alignment avoids "cacheline ping-pong", as it's called, whenever two CPUs need to access "their" element of the same array at the same time.
- as to the MHz -- there was a wraparound bug if your CPU is faster than 2 GHz (highest signed 32-bit int), which isn't a problem today but will be tomorrow.
- Tigran's microcode driver -- some small changes were made so that it could be used for P4's.
- maybe they'll need to patch lm_sensors to accommodate the increased temperature range since the P4 runs so hot. (: (:
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