AT&T 6300+ add-in disk problem!

[Samuel Wilson]

Ahem.  This friend of mine...  has an AT&T 6300+ with an extremely
awkward disk configuration: it has a Western Dig.  WX1002 controller
(i.e. an 8-bit card), a miniscribe 40 meg drive, and DiskManager
software.  Under AT&T DOS 3.2 the performance is *terrible* -- about
.5 the speed of an IBM-XT according to Norton SI v.4.  The disk is
fast enough, and the computer is fast enough, but the controller card
/ Diskmanager software / DOS version / ROM version software is a
disaster.

What can I (I mean, he) do?  I don't care if the disk is partitioned
into several drives, but I need more speed.  What is AT&T's solution
to this?  Is there another disk controller card, or is the controller
built into the motherboard?  If so, how does one tell it what kind of
disk one has?

[ps. without Diskmanager things are no faster;  under AT&T DOS
3.1 things are no (?) faster]

Thanks,
Sam Wilson
    wilson at cunixc.cc.columbia.bitnet
                             .edu