Messages in this thread | | | Date | Thu, 6 Feb 2003 15:21:12 -0500 (EST) | From | Bill Davidsen <> | Subject | Re: HYPERTHREADING on older P4??? |
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On Wed, 5 Feb 2003, Dave Jones wrote:
> It means there is one 'thread'. Ergo, you do not have the possibility > of running this as you would a true HT P4. There are a limited number > of Northwood P4's out there which do support HT and have >1 sibling, > but asides from those, you'll need a Xeon to take advantage of it.
The 3.06G parts are pretty available, but the prices are just getting silly. I suppose it will drop when the supply of parts exceeds the demand of people who can't wait.
> There are countless rumours of being able to enable extra siblings > by poking MSRs, but not one person has to my knowledge achieved this. > Some folks have also allegedly found that snipping pins or wiring extra > bits to them have enabled the 'extra sibling'. Whether this is true or > not, and whether it is 100% equivalent to a real HT part is again, > questionable.
There is one "fix" going around which supposedly works using the firmware upgrade capability. I have no idea if it does or even could work, I never had the guts to try it, because I'm not sure that changes really go away on power cycle, and I didn't get it from a trusted source. The idea of untrusted code running in the firmware is scarier than booting Windows.
On Wed, 5 Feb 2003, Mikael Pettersson wrote:
> HT-capable P4s decide at RESET (or INIT?) time whether to enable > the second thread or not by sampling one of the data or address pins. > The chipset is supposed to drive that pin low or high according to > how HT has been set up in the BIOS. This is mentioned in the > 3.06 GHz P4 data sheet.
This is my understanding, and it makes the idea of a firmware fix sound more possible, by just enabling the 2nd sibling if HT capability exists. I'll still let wonone else check it out first...
-- bill davidsen <davidsen@tmr.com> CTO, TMR Associates, Inc Doing interesting things with little computers since 1979.
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