Image source: HP, edited by the author.

What: Shares of HP (NYSE:HPQ) fell 53.5% in November, according to data from S&P Capital IQ. Any stock chart service will give you the same hair-raising plunge. But of course, there's a perfectly reasonably explanation for this. The old HP is now two separate businesses, and these simple charts and figures don't take the new Hewlett-Packard Enterprise (NYSE:HPE) ticker into account.

So what: Hewlett-Packard Enterprise sprung into existence at the very start of November, in the tax-free form of a share dividend paid out to current HP shareholders.

The Silicon Valley beast was no longer a single entity with a $50 billion market cap, but two smaller operations with individual market caps in the $20 billion to $30 billion range.

Through a few ups and downs along the way, both of the new HP stocks ended November roughly 5% higher than their monthly opening levels. That was enough to beat the S&P 500 market index, which traded roughly sideways during this period.

And nobody lost 50% here. It's a mirage, but one etched into HPQ's stock charts forevermore.

Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

Now what: At one point, Hewlett-Packard Enterprise was lagging behind the markets and its corporate sibling while HP raced ahead to a 20% November gain. Fourth-quarter results quickly brought the consumer-oriented stock down to earth while boosting the enterprise operation, bringing everyone back to square 1.

If nothing else, that report reminded shareholders how little things had really changed from the single-ticker days. As CEO of one company and chairman of the other, Meg Whitman still pulls all the strings here. More than $1 billion of the two companies' $26.4 billion in total sales came from inter-segment transactions, meaning that 4% of HP's business was funded by other HP units.

The two companies should eventually start drifting apart -- if Whitman will allow it. That's the real test of how effective this business split really was. For now, it's very much business as usual, and that's not a compliment at all.