I want to know what company manufacturers the Ethernet controller chip
on a D-Link DGE-550T Gigabit network board. The OEM setup information
in a readme file provided on the CD-ROM along with the device drivers
provides this data:

; This INF file is used to install LAN adapter driver for Windows NT.
;
;   Supported OS: Windows NT 4.0
;   Supported Adapters:
;
;       D-Link DGE-530T Gigabit Ethernet Adapter.
;
;   Copyright (C) 2003 D-Link Corporation. All rights reserved.
;
;*****************************************************************************
;   Revision #: 1.1.30404$
;*****************************************************************************
;*****************************************************************************
;   Customization constants
;*****************************************************************************
[ModelConstants]
    IHVName             = "D-Link"
    ModelDescription    = "DGE-530T Gigabit Ethernet Adapter"
;    Ndis3Drvr           = "M4CXNT4.SYS"
    Ndis4Drvr           = "M4CXNT4.SYS"
    CfgFileName         = "M4CXCFG.DLL"
    DrvrMajVer          = "6"
    DrvrMinVer          = "0"
    ModelCode           = "M4CX"
    VendorID            = 4486         ;; 0x1186 (D-Link)
    AsicCFID            = 1275072902   ;; 0x11864C00 = 1275072902
    DeviceID            = 19456        ;; 0x4C00 = 19456
; ***************************************************************

I was hpeful that the "AsicCFID=0x11864C00" code might be a clue to
the chip manufacturer, but I am unable to find a mapping of this hex
code number to a list of manufacturers.

In addition, the face of the chip itself is labelled as follows:
Logo: two stylized A?s side-by-side (at least they kind of look like A's)
Line 1:  88E1000-RJJ
Line 2:  DD10650.6
Line 3:  0329 CDP

So who manufacturers that chip?

Hi,
Too bad I'm not an official researcher now as that one was easy.
The manufacturer you're looking for is Marvell Technology Group Ltd.
The chip is part of the "alaska" family.
More infos at:

http://www.marvell.com/products/transceivers/singleport/88e1000.jsp

Hope it helps
Best regards

Did you do a MAC address lookup?