This is different from what used to be a Timer A value of 6 in the 6526 CIA in the original Commodore 1571. The 5710 CIA does not contain timer or timer control registers. It only contains two port registers and the register to control the serial shifter and its event. In addition to the aforementioned alarm clock interrupt bug, many CIAs exhibited a defect in which the part would fail to generate a timer B hardware interrupt if the interrupt control register (ICR) was read one or two clock cycles before the time when the interrupt should have actually occurred. This defect, as well as logic errors in the Commodore provided (8 bit) operating system, caused frequent pseudo-RS-232 errors in the Commodore 64 and Commodore 128 computers when running at higher baud rates.