Bren Higgins
Executive Vice President and Chief Financial Officer at KLA
Thanks, Rick. Our results demonstrated the consistent execution of our global team. Despite the challenges and complexity of the current industry environment, KLA continues to show resource and the ability to adapt to meeting customers' changing and fluid requirements. Revenue was $2.49 billion, slightly above the guidance midpoint of $2.45 billion. Non-GAAP diluted EPS was $6.16, above the midpoint of the guided range of $5.26 to $6.46. GAAP diluted EPS was $4.28. GAAP EPS was negatively impacted by $1.59 for goodwill and purchased intangible asset impairment charge.
Non-GAAP gross margin was 62.6%, just above the high end of the guidance range of 60.5% to 62.5%. Non-GAAP operating margin was 40.7%. The Quarterly non-GAAP net income was $839 million, GAAP net income was $583 million. Cash flow from operations was $622 million, and free cash flow was $545 million.
As I just mentioned, during the quarter, KLA recognized a goodwill and purchase of intangible asset impairment charge of $219 million for the PCB and display reporting unit attributed to a weaker long-term outlook, primarily for the flat panel display business. We have begun investigating strategic alternatives for this business, which accounted for 1.4% of total revenue in calendar 2023. The breakdown of revenue by reportable segments and end markets and major products and regions can be found within the shareholder letter and slides.
Turning to the balance sheet; KLA ended the quarter with $3.3 billion in total cash, cash equivalents and marketable securities, debt of $5.95 billion and a flexible and attractive bond maturity profile supported by strong investment-grade ratings from all three agencies. In December 2023, Fitch rating upgraded KLA's debt rating to A from A- with a stable outlook.
Moving to our outlook; looking ahead to calendar 2024, the exact timing of a meaningful and sustainable resumption in WFE investment growth continues to remain uncertain. Though there are signs of improvements in some end markets, this improvement is off low levels, impacting our customers' profitability and cash flow generation in the near term. KLA's overall demand is stabilizing around current business levels, plus or minus the guidance ranges. As of now, this translates into KLA revenue bottoming in the March quarter, driven mostly by a customer project delay occurring in the last couple of months.
Based on current fast schedules in our June quarter shipment plan, we expect sequential growth to return in the June quarter and continue for the remainder of the calendar year. For calendar 2024, we currently expect WFE demand to be in the mid- to high $8 billion, roughly flat to modestly up from the anticipated level in calendar year 2023. We expect that the second half of the calendar year will be stronger than the first half for WFE investment. This WFE estimate reflects our current top-down assessment of industry demand as follows: In memory, we expect WFE investment to be slightly up from low levels with investments focused on high bandwidth memory capacity and leading-edge node development.
Both NAND and DRAM fabs are still a low utilization levels as consumer markets have not yet returned to the growth levels needed to bring factory utilization back to the high levels seen in recent years. Once customers consume this excess capacity and focus on node migration, we would expect to see new investments. Foundry logic is expected to be slightly up with leading-edge investment returning to modest growth levels, Legacy investment declining versus 2023 and China Legacy node investments remaining relatively flattish to current levels.
As for guidance, KLA's March quarter guidance is as follows: Revenue is expected to be $2.3 billion, plus or minus $125 million. Foundry Logic is forecasted to be approximately 60%, and memory is expected to be 40% of semi process control systems revenue. Within memory, DRAM is expected to be about 85% of the segment mix and NAND the remaining 15%.
Non-GAAP gross margin is forecasted to be in a range of 61.5% plus or minus 1 percentage point as product mix weakens quarter-to-quarter due to lower overall semiconductor process control systems revenue. For calendar 2024, based on current industry outlook, top line growth expectations, higher forecasted growth in services and expected systems product mix we are modeling gross margins to be relatively stable around the mid 61% range to what we delivered in 2023. Variability quarter-to-quarter is typically driven by product mix fluctuations.
Operating expenses are forecasted in the March quarter to be approximately $545 million, relatively flat with the December quarter. Our calendar 2024 operating expenses, we expect $5 million to $10 million incremental growth per quarter beyond the March quarter, in line with expected sequential growth in revenue. Prototype material purchases can drive variability quarter-to-quarter.
For the calendar '24 tax rate based on current forecast, we do not expect material changes. You should continue using the 13.5% effective rate for modeling purposes. Other model assumptions for the March quarter include other income and expense net of approximately $45 million. GAAP diluted EPS is expected to be $4.93 plus or minus $0.60. A non-GAAP diluted EPS of $5.26 plus or minus $0.60. EPS guidance is based on a fully diluted share count of approximately 135.6 million shares.
In conclusion, we are optimistic that most end markets are showing signs of improvement. KLA will remain focused on supporting customers, executing on our product road map and positioning the company for a return of growth at the leading edge. The visibility into the precise timing of a sustainable demand recovery is still unclear. KLA is running the business to ensure delivery of a differentiated product portfolio that meets customers' technology road map requirements and to execute our business in line with our longer-term growth expectations.
The KLA operating model guiding best-in-class execution, KLA continues to implement strategic objectives, which are geared to drive outperformance. With a focus on customer success, delivering innovative and differentiated solutions and operational excellence, KLA is able to deliver industry-leading financial and free cash flow performance and return capital consistently. The past few years have strengthened our confidence in the increasing importance of process control and enabling technology advancements and optimizing yield at a high design mix volume production environment. This bodes well for KLA's long-term growth outlook despite still challenging near-term demand trends. In the meantime, KLA business continues to stabilize and the long-term secular trends driving semiconductor industry demand and investments in remain very compelling.
That concludes the prepared remarks. Kevin, let's begin the Q&A.