これはSK計算機室のテストベンチを用いた検証結果です。

K-Log#36698
https://klog.icrr.u-tokyo.ac.jp/osl/?r=36698
> Remaining concern
> Only remaining concern is that it takes a few hours for synchronizing IRIG-B when a cold boot of the front-end computer is performed. In the past, similar things often occurred when down time became so long and a room temperature changed largely maybe because it took long time to be stable in the temperature of a crystal oscillator of timing slave. On the other hand, in this time, it takes long time even when a down time is only a few seconds. Such a thing wasn't reproduced in the test bench. So we have no idea to solve this issue now.

IRIGB_TIMEの異常な動きは、SK計算機室でも再現することができた。

原因は、IRIG-Bカードにあると考えている。
正常に動作するテストベンチを用いて、IRIG-Bカード(S/N:3799)に交換すると、値が減少と増加が見られた。
その後、旧IOシャーシ(V1 IO Chassis)に交換しても発生した。

SKにある上記以外のIRIG-Bカードでは不具合は発生していない。
02181
3796
02174
3793
02158
02172
 => フルハイトのままslot2で試験、これ以外はすべてLowpro
02171
 =>LED黄色と緑色が点灯して黄色が消えない、（このカードは接続壊れている？）

以上から、この問題は、IRIG-Bカードの個体毎の問題と考えている。

---
These are the results of verification conducted using the test bench at the SK Computer room.

K-Log#36698
https://klog.icrr.u-tokyo.ac.jp/osl/?r=36698
> Remaining concern
> Only remaining concern is that it takes a few hours for synchronizing IRIG-B when a cold boot of the front-end computer is performed. In the past, similar things often occurred when down time became so long and a room temperature changed largely maybe because it took long time to be stable in the temperature of a crystal oscillator of timing slave. On the other hand, in this time, it takes long time even when a down time is only a few seconds. Such a thing wasn't reproduced in the test bench. So we have no idea to solve this issue now.

The abnormal behavior of IRIGB_TIME could also be reproduced in the SK computer room.
We believe the cause lies in the IRIG-B card itself.
Using a test bench that operates normally, when the IRIG-B card (S/N: 3799) was installed, both decreases and increases in the value were observed.
Afterward, the issue still occurred even when replacing the system with the old IO chassis (V1 IO Chassis).
No issues have been observed with the following IRIG-B cards at SK computer room:
02181
3796
02174
3793
02158
02172
=> Tested in slot 2 with full-height configuration; all others are Low-profile
02171
=> Both the yellow and green LEDs light up, and the yellow LED does not turn off (possible connection failure on this card?)

Based on the above observations, we believe this issue is specific to individual IRIG-B cards.