Read and write Mac disks from Windows with MacDrive 98.
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Regarding previous reports (a and b) of startup delays (of about 30 seconds, during which time the computer screen remains black and the drive does not spin up) on certain Mac models (such as the Power Mac 6400) running Mac OS 7.6.1 or later: a. A UMAX Design Engineer writes: "I have consistently seen the black screen startup delay on Tanzania based motherboards using certain IDE hard drives. The startup delay is associated with the amount of time that the drive takes to report being ready. (Asserting the IOCHRDY signal on the IDE bus.) I have a drive that takes up to 20 seconds to become ready. This drive also has an LED that indicates when the drive is ready. When the system is powered on the screen stays black until the drive LED shows that it is ready. Technically this is an incorrect implementation of the IDE bus protocol. The IOCHRDY is meant to indicate that the device is ready to communicate with the system and not necessarily that the device is ready to operate. My assumption is that the Tanzania ROMs wait until the IDE bus is ready before moving on to enabling the screen and that certain drives and drive firmware revisions assert IOCHRDY at different times when powering up the first time. I have not been able to reproduce this problem on an Alchemy board. b. Robert Blumenkranz (of ClearPhone) writes: When starting up the 6400 computer if you are experiencing delays, and black screens, check the voltage on the Clock battery. I discovered that my 6400 was not turning on and the monitor remained black. Even the green "On" light on the front panel did not turn on. The culprit was the Alkaline Clock battery. It is labeled 4.5 Volts and when I measured the voltage it was 4.1. For some reason the battery did not last. So I made up a battery pack from 3 alkaline 1.5 volt AA cells. That did the trick and it will last a lot longer. Now the computer turns on right away and everything is fine. It appears that the voltage of this battery is critical to the complete boot up of the 6400. Here is what may be happening. As the battery voltage gets lower and into the critical range (i.e., 4.0 volts instead of 4.5 volts), it will not allow the 6400 to start up fully. You will hear the bong startup sound because the processor will do that even if the battery is bad. If the battery is low, the monitor stays black until the voltage builds up to the point of triggering the startup procedure. This then allows the computer to turn on. As the battery ages the voltage drops and this condition will become more and more apparent on the 6400 (and perhaps other models) until the computer will not boot up at all. When this happens the screen will stay black after the bong sound. By then it is too late and you will need a new battery before you can run the computer. There are two possibilities that are causing this problem.
It should be noted that this battery is much larger than earlier models and this may be because it needs to supply more current for this processor. Early failure could mean real problems for everyone using these Macs. | |