Continued testing Virtual 2315 Cartridge Facility in real mode, using the IBM 1130 internal disk drive

BELT TENSIONED AND DRIVE NOW SPINNING UP

I discovered a much better access method to reach the motor bracket bolts for tensioning the drive cable. It involves opening the back cover, swinging both logic gates completely out, then crawling into the machine from where the gates normally sit. The adjustment went smoothly and now the drive spins up properly.

I set up again to run the disk tests with the Virtual 2315 Cartridge Facility (V2315CF) in real mode, using the physical disk drive in addition to the virtual cartridge image. The 1130 powered up, the V2315CF loaded the cartridge image, and I flipped on the disk drive power switch to start it spinning. 

SENSE BIT TESTING BEFORE HEADS LOAD

Before the drive was turned on, I performed an XIO (eXecute Input Output) instruction of type Sense DSW to see the status bits for the device. They showed it not ready (bit 2 is on) with the arm at the Home (cylinder 0) position (bit 4 is on). I didn't see the sector count changing, which they should be doing as the drive spins up. 

HEADS LOADED BUT NO FILE READY INDICATOR

When the File Ready lamp turns on, another Sense DSW would show the drive with only the Home bit turned on, plus the bottom two bits would indicate the sector approaching the heads at the instant of XIO execution. The ready lamp never lit. 

When I issued another XIO Sense Device, the drive still showed not ready and at the home cylinder, but also bit 0 was turned on. This is the error status and it has several causes:

1. During a read or write operation, the error checking bits indicated an error for at least one word
2. The drive was still doing a read or write sector when the next sector arrived under the head
3. A write select error occurs when both heads are selected for writing or other electronics failure
4. The drive set the power unsafe latch usually due to inadequate RPMs but also if power sags

Since we had not attempted either a read or a write, we are left with either electronics failure (3) or the power unsafe latch being set. During my tabletop testing of the drive, I saw this failure which was a consequence of omitting a jumper between 48V and system ground on the back of the disk drive.

WILL MONITOR THE LOGIC SIGNALS COMING FROM THE INTERNAL DISK

I will check the logic state (voltages) for the signals coming from the 13SD internal disk electronics, ensuring that they are reasonable for the state of the drive. I can monitor the sector and index pulses plus test the power unsafe latch condition. I ran out of time today as I had to spend most of the day at the Sands History Center working on the museum display systems. 

INTERRUPTED THE UNLOCK LAMP WIRE IN ORDER TO SUPPORT VIRTUAL MODE

The Unlock lamp is wired to 48V inside the console of the 1130 and the other end is a wire that connects to the disk drive. When the drive is not turning, the unlock solenoid is activated by a circuit pulling one end of it to ground. The same circuit also pulls the wire to the unlock lamp to ground. This causes the lamp to light when the 13SD internal disk drive is not spinning.

For virtual mode, we will not have the motor of the physical drive turning, thus the unlock solenoid will always be at ground. In virtual mode, we want to turn the 1130 console lamp on and off based on whether we are simulating the drive turned off or simulating a spinning drive as a cartridge is loaded. 

To do this, the Virtual 2315 Cartridge Facility (V2315CF) interface board has a relay that is activated by the virtual position of the real/virtual switch on that board. When the relay is not activated, the wire from the physical drive is connected to the console Unlock lamp. When activated, the relay connects the Unlock lamp to an FET on the interface board. The FET is turned on and off by a signal from the V2315CF logic, either grounding the lamp to light it or leaving it floating (off).