Thread: Intel Xeon PHI?
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Old 2020-12-05, 16:44   #150
kriesel's Avatar
Mar 2017
US midwest

5,087 Posts

Highest indicated clock rate I've seen from the Xeon Phi 7250 is 1.55 Ghz (Windows Task Manager, a small fraction of the cores in use). Square waves have odd harmonics of the fundamental frequency with declining amplitude. So up to 1.55, 4.65, 7.75....Ghz at amplitude 1, 1/3, 1/5,... How high should be blocked by screening to replace the side panel?
The removable side panels are nonmagnetic, as are top, front, and bottom. Back panel and power supply case are magnetic; back panel has about 200 quantity 6mm hexagonal holes closely spaced for ventilation. Presumably that constitutes a sufficiently bad slot antenna. Assume that perforated aluminum or steel for a new side panel can have the same size hole (that electrical vs. magnetic shielding is not an issue).

Slots are of order 0.1 wavelengths wide by 0.5 wavelengths long in slot antenna use.
6mm/0.1 = 60mm corresponding to an estimated upper bound of 300e6m/sec/.06m = 5Ghz, only 3.2 times the maximum observed clock rate, which seems rather low.

Typical microwave oven frequency is 2.45GHz. There the shielding has holes ~2mm in size. 0.002m / ( 300e6m/s / 2.45e9/s ) = .002/.122 = 0.016 wavelengths.

These results suggest that for somewhat quieting the EMI from a miner frame system, with 3+Ghz CPU and up to ~1.8Ghz gpus, hardware cloth with its 1/4" wire pitch would be a much better choice than 1"x2" aperture welded wire fence roll, for constructing a 5-sided cover shield.

Last fiddled with by kriesel on 2020-12-05 at 16:58
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