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From: magnus.thelander@jetset.ct.se (Magnus Thelander)
Newsgroups: comp.sys.amiga.hardware
Subject: A2620 Jumpers.
Message-ID: <2dd871ee@jetset.ct.se>
Date: Tue, 17 May 94 01:27:00 +0200
Sender: news@jetset.ct.se
Reply-To: magnus.thelander@jetset.ct.se
Organization: Home of uugate, the OS/2 Internet/Fidonet gateway
Lines: 27


 SEB> anything else about the card.  Any information (jumper functions and
 SEB> settings, how to disable card, etc.) is very much appreciated.

C= A2620 Jumper configuration
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

J302 must be installed for proper operation on 4-layer motherboards.

J200 specifies the clock used by the 68881 FPU. As shipped, the FPU uses the
basic 14.3 MHz clock also used by the 68020 and 68851. If a faster 68881 or
68882 is installed with the appropriate crystal module, moving J200 to the
lower  position will route that module's output to the 68881.

J301 specifies the amount of RAM installed in the A2620. When no jumper is in
place, the system expects 2 megabytes. With the jumper in place, the system
expects 4 megabytes.

J303, when installed, disables all A2620 DRAM.

J304 selects which operating system to autoboot. When no jumper is in place,
the system autoboots Amiga DOS. With the jumper in place, the system autoboots
UNIX (assuming you have UNIX on a hard drive or tape drive).

J500, as shipped, sets the RAM timing to 100 nanoseconds. Moving it requires 80
nanoseconds DRAM.