SecProbe.io

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549

       DIVISION OF
CORPORATION FINANCE

 December 30, 2010
  Mr. James W. Sullivan Chief Financial Officer Mosys, Inc. 755 North Mathilda Avenue Suite 100 Sunnyvale, California 94085

 Re: Mosys, Inc.
Form 10-K for the Fiscal Year Ended December 31, 2009 Filed March 26, 2010 File No.  000-32929
Dear Mr. Sullivan:

We have reviewed your filings and have the following comments.  In some of our comments,
we may ask you to provide us with information so we may better understand your disclosure.

Please respond to this letter within ten busines s days by providing the requested information,
or by advising us when you will provide the requested response.  If you do not believe our comments
apply to your facts and circumstances, please tell us why in your response.

After reviewing the information you provide in response to these comments, we may
have additional comments.

Mr. James W. Sullivan
Mosys, Inc. December 30, 2010 Page 2

Form 10-K for the year ended December 31, 2009

 Financial Statements, page 49

 Note 1: The Company and Summary of Significant Acc ounting Policies, page 55

 Revenue Recognition, page 58

 1. We note your disclosure that for license ag reements that do not require significant
development, modification, or customization, revenues are generally recognized when the
revenue recognition criteria have been met.  Please revise futu re filings to clearly explain
when in the sales process you have met the r ecognition criteria and recognized the related
revenues.  Please provide us with your proposed  future disclosure.  Also, tell us why you
use the word “generally” in the aforemen tioned disclosure.  If you recognize revenue
other than when the revenue r ecognition criteria have been met, please describe those
circumstances and your rationale fo r using such an accounting policy.

2. We see that you provide unspeci fied upgrades under certain ag reements.  Please explain
the nature of the upgrades, the related ag reements and how you account for the upgrades
offered.

Note 4: Revision of Prior Period Financial Statements, page 66

 3. We see that you identified a calculation erro r in your determination of stock based
compensation expense that led to an unders tatement of previously reported non-cash
stock based compensation expense for 2008, 2007 and 2006 and the quarters within those
years and also changed the timing of stock based compensation expense.  We also see
that you determined that this error was determ ined to be immaterial to those previously
reported financial results, but you retroac tively corrected those related financial
statements.  It appears from your table,  however, that your adjustments may be
quantitatively material to cer tain line items in certain periods.  Please tell us how
management concluded these adjustments were  not material to each related period and
provide us with your complete  SAB 99 and SAB 108 analysis.

Form 10-Q for the Quarterly Period Ended September 30, 2010

Note 1. The Company and Summary of Si gnificant Accounting Policies, page 6
 Goodwill, page 8

 4. We note from your disclosure that you review goodwill for impairment annually in the
third quarter.  Please tell us the outco me of your goodwill impairment test as of

Mr. James W. Sullivan
Mosys, Inc. December 30, 2010 Page 3
 September 30, 2010.  From your disclosure on page 34 in your Form 10-K for December
31, 2009 we note where you state that “the fair value of each reporting unit is determined
using the market approach,” which appears to imply that you used more than one reporting unit for your annual impairment test  in your fiscal year ended December 31,
2009.  However, on page 8 in your Form 10-Q for the quarterly period ended September
30, 2010 you state that “[you] estimate the fair value based on the market value of the
reporting unit at the entity level,” which appe ars to imply that you used one reporting unit
as of September 30, 2010.  In this regard, pleas e identify each reporting unit used in your
goodwill impairment test for the fiscal year ended in 2009 and 2010.  Please explain to us how you determined the number of reporting uni ts used in your goodwill impairment test
in each of the fiscal years ended in 2009, and 2010, explaining your rationale for the differences between both years.  Clearly tell us how you have defined your reporting
units for 2009 and 2010, including your reasons as to why discrete financial information
is not available at a lower leve l than the entity level.

5. In this regard, we note from page 34 in  your Form 10-K for December 31, 2009, that
goodwill impairment is one of your critical ac counting policies, and that if your stock
price continues to experience significant pri ce and volume fluctuations, this will impact
the fair value of the reporting unit, which can lead to potential impairment in the future periods.  Considering the uncertainty in th is accounting estimate, for each reporting unit
that is at risk of failing step one of the goodwill impairment test as defined in ASC Topic
350, please provide us with and disc lose in your future filings:

 The percentage by which fair value exceeded carrying value as of the date of the most
recent test;
 The amount of goodwill allocated to the reporting unit;
 A description of the methods and key assumptions used and how the key assumptions
were determined;
 A discussion of the degree of uncertainty associated with the key assumptions. The
discussion regarding uncertainty should provide specifics to the extent possible (e.g.,
the valuation model assumes recovery from a business downturn within a defined
period of time); and
 A description of potential events and/or changes in circumstances that could
reasonably be expected to negatively affect the key assumptions.

    We urge all persons who are responsi ble for the accuracy an d adequacy of the
disclosure in the filing to be certain that the filing includes all in formation required under
the Securities Exchange Act of 1934 and th at they have provided all information
investors require for an informed invest ment decision.  Since the company and its
management are in possession of all facts re lating to a company’s disclosure, they are
responsible for the accuracy and adequacy of the disclosures they have made.

Mr. James W. Sullivan
Mosys, Inc. December 30, 2010 Page 4
  In connection with responding to our comments, please provide, in writing, a
statement from the company acknowledging that:   the company is responsible for the adequacy  and accuracy of the disclosure in the
filing;
  staff comments or changes to disclosure  in response to staff comments do not
foreclose the Commission from taking any action with respect to the filing; and
  the company may not assert staff comments as a defense in any proceeding initiated
by the Commission or any person under the federal securities laws of the United States.

In addition, please be advise d that the Division of Enfo rcement has access to all
information you provide to the staff of the Divi sion of Corporation Fi nance in our review
of your filing or in response to our comments on your filing.
You may contact Julie Sherman at (202)  551-3640 or me at (202) 551-3212 if you
have any questions regarding th ese comments.  In this regard , do not hesitate to contact
Martin James, Senior Assistant Chief Accountant at (202) 551-3671.

        S i n c e r e l y ,                                     Jeff Jaramillo          B r a n c h  C h i e f