Newsgroups: comp.sys.att
Subject: Re: 3b/400 speedups
From: rthomas@hakatac.almanac.bc.ca (Robert N Thomas)
Date: Thu, 31 Dec 92 06:31:51 GMT
Distribution: usa
Organization: Sir HackAlot's Castle BBS, Port Alberni, B.C., Canada

In article <1992Dec30.013201.16831@hakatac.almanac.bc.ca> rthomas@hakatac.almanac.bc.ca (Robert N Thomas) writes:
>    There is one person...   Jeff Hakner  hak@alf.cooper.edu has posted
>a message here detailing that he has been successful at expanding a 3B2/310
>to 6 MB of ram.  This type of procedure could also be done to 3B2/400's as well.
>
>P.S. - I still have his post and could re-post it...

   I was asked to re-post this be a few people, hence the following is 
Jeff's original (But still very interesting) article...

---------------------------------------
Newsgroups- comp.sys.att
From- hak@alf.cooper.edu (Jeff Hakner)
Subject- YES!! 6MB on a 3B2/310, DONE!!
Organization- The Cooper Union ( NY, NY )
Date- Sun, 15 Nov 1992 02:34:47 GMT

Well, I've done it!!!  I've modified a Mezzanine Memory Board
from Congruent Technologies (which is designed to allow the use
of one 2MB and two 1MB boards in a 3B2/300,310 or 400) and added
a little glue logic to come up with a mod that delivers breaks
the 4MB barrier on a 3B2/300,310 or 400.  My guess is that I've
re-discovered the mods previously done in the legendary (perhaps
mythical) Olivetti product.  You don't believe me?  Well:

3B2 SYSTEM HARDWARE CONFIGURATION:

Memory size: 6 Megabytes
System Peripherals:

        Device Name     Subdevices              Extended Subdevices

        SBD
                        Floppy Disk
                        72 Megabyte Disk
                        30 Megabyte Disk
        SCSI
         (S.E. BUS ID0)
        *VOID*
        EMD
        MAU

This is the prtconf from my 3B2/310, running SVR4.1ES.

Now, the bad news.  This mod is not for the timid.  It required
attaching several jumper wires to the motherboard and jumpering
and trace-cutting the Congruent Mez board, including a trace
which had to be cut in the buried layer of that 3-layer board.
However, the hardware hacks are reversible (no trace cuts on
the motherboard).  The 3B2 firmware doesn't automatically detect
the extra memory.  Since I can't modify the firmware (without
messy disassembly and patching), I recompiled filledt to handle
the auto-resize.  I can do this because we have a source code license.
Other than that, no OS patches were needed, but
your mileage may vary on earlier releases.  Finally, the cost
may be prohibitive.  Congruent gets $500/ea for the Mez boards!!
This is a lot, IMHO, for a totally passive board with 5 connectors,
even though it is a 3-layer PCB.

I will be posting further details on this mod (including how to do it),
but first I'd like to tidy up some loose ends.  For example, the glue
logic is currently sitting on a breadboard *outside* the machine,
and is implemented with 3 74LS series TTL chips.  I'm going to blow
a PAL to handle the logic.  I'm also trying to figure out how to
get 8MB into the system.  The limitation is purely mechanical.

Thanks to those out there who helped me out on this!


--Jeff Hakner
Systems Adminstrator
Cooper Union



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