Success Rate: 50%
For this test, we used four different mainboards: an Intel D845EBT (845E), an AOpen AX4B Pro-533 (845E), a Gigabyte GA-8IEXP (845E) and an MSI 6586 (SiS648).
The Intel board uses the first-generation 845E chipset and stands out because of its completely automated BIOS update in Windows, which we used to run BIOS Version P06. Despite PowerLeap's express insistence that it was compatible, we were only able to run the Pentium 4 with Hyper-Threading without the iP4-Adapter - without HT, naturally, which was a disappointment.
The second candidate was the AX4B Pro-533 from AOpen, which also uses the Intel 845E chipset. The current stepping is suited to HT, but not this board. We ran BIOS Version 1.15, which actually allowed operation with HT.
Candidate Three was Gigabyte's 8IEXP. According to Gigabyte, only Version 2.0 is suited for HT; but we still put our 1.1 to the test and flashed the BIOS with Version F9 from November of last year. After installing the iP4, the board actually ran in HT mode without any problems.
The fourth board, the 648Max from MSI, did not work. Unlike the other three models, this board uses an SiS chipset. This too was only recently released by the manufacturer for HT. Running the BIOS Version 1.5 did nothing, as expected, as this version was intended for non-HT boards. We tried the BIOS Version 3.1, however, which, according to the website, is not in any way suitable for our "old" 648Max (without HT). And in fact, with the adapter, the board showed no image. But without the adapter, it only showed a confused array of characters: this is proof that the BIOS could enable Hyper-Threading, which the chipset could not handle.
In general, therefore, we cannot really speak of the ultimate Hyper-Threading adapter; only two out of the four boards ran the way we wanted them to. It should also be mentioned, as a word of caution, that the latest BIOS versions should not be run on older boards of the same type. The latest BIOS versions support HT, but possibly not the chipset. As a result, after that your system will usually only start if you insert another processor - without HT.