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                                                                     EXHIBIT 5.1


                 [ALLEN, MATKINS, LECK, GAMBLE & MALLORY LLP]



                                 May 14, 1996



Alpha Microsystems
2722 South Fairview Street
Santa Ana, California 92704

Gentlemen:

        At your request, we have examined the Registration Statement on Form S-3
filed by you (File No. 333-3167), and the form of Amendment No. 1 thereto to be
filed by you, with the Securities and Exchange Commission in connection with
the registration under the Securities Act of 1933, as amended, of 4,442,069
shares of Common Stock, no par value (the "Shares"), of Alpha Microsystems, a
California corporation (the "Company"), issuable upon exercise of certain
outstanding warrants to purchase shares of Common Stock as described therein.
The Registration Statement as amended by Amendment No. 1 is hereinafter
referred to as the "Registration Statement."

        We are familiar with the proceedings taken by you, and with the
additional proceedings proposed to be taken by you, in connection with the
authorization and proposed issuance and sale of the Shares. Based upon the
foregoing, we are of the opinion that under California law, subject to the
additional proceedings being duly taken and completed by you as now
contemplated by us as your counsel prior to the issuance of the Shares, upon
the issuance and sale of the Shares in the manner contemplated by the
Registration Statement, the Shares will be legally issued, fully paid and
non-assessable securities of the Company.

        We consent to your filing this opinion as an exhibit to the
Registration Statement and to the reference to our firm in the Prospectus
incorporated therein under the caption "Legal Matters."

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Alpha Microsystems
May 14, 1996
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                                Very truly yours,


                                /s/ ALLEN, MATKINS, LECK, GAMBLE & MALLORY LLP.
                                -----------------------------------------------
                                Allen, Matkins, Leck, Gamble & Mallory LLP.,
                                a Limited Liability Partnership including
                                Professional Corporations

JDG/rek