[SPARCbook] What is the Max Ram for 3GX....???

[Thomas Roehr]

Just pick up a couple of those sim adapters that let you plug 2 or 4 sims into one
slot. They have jumpers to configure the memory layout. No battery, but you can
ahve 256 MB's of ram. They are only about $20 each.

Tom Roehr
troehr at nj-onramp.com

Bob Krzaczek wrote:

> Thus spake Ken Hansen:
> ; You can not *stuff* 256 Meg of RAM in a SPARCbook 3GX
> ; without *severe* hardware hacking, of they type that
> ; would *probably* render your laptop no longer
> ; portable.
>
> Severe?  Sure.  Unportable?  "Nahhhhhhhh" :)
>
> Actually, just before I moved onto a different laptop, I was
> considering exactly this project on my 3GX.  It really shouldn't be
> *too* hard (of course, I say that with the confidence of someone who
> no longer plans on doing the work).
>
> In the event that there's a hw hacker or two on this list, let me
> encourage you!
>
> Consider: the microSparc-II cpu in the 3GX has a nice, friendly,
> simple DRAM controller integrated right into it.  It should be fairly
> straightforward, using Sun's own documentation on the CPU (available
> as a PDF from their web site), to trace back the signals from the SIMM
> socket and determine which memory control lines (the various RAS, CAS,
> and high address lines) are where on the SIMMs.
>
> At that point alone, one could guess what was different about the
> Tadpole 64M SIMMs.  Sure, we know they appear as two 32MB SIMMs to the
> hardware; but, also bear in mind that a 32MB SIMM is really two 16 MB
> SIMMs. So, expect a little weirdness here; at a guess, I'm betting on
> seeing some weirdness with an extra RAS line from the CPU stealing an
> unused line on the SIMM socket.  Either way, it shouldn't be too hard
> to figure out exactly how the 3GX SIMM sockets were wired wrt. to the
> DRAM controller.  From that, I one shold be able to infer how the
> special 64M SIMMs were set up.
>
> At that point, things can go one of two ways.
>
> If you're lucky.  Super lucky.  More lucky than you have any right to
> expect, you might discover that some existing 64MB SIMMs could be
> modified to match Tadpole's design.  This would almost certainly
> require one of the "chip heavy" 64MB SIMMs; that is, a SIMM with many less
> dense chips, rather than a few dense chips.  Sadly, most 64MB SIMMs
> are exactly this latter catgeory.
>
> So, the odds are a little against you there.
>
> The alternative, of course, is that you could add SIMMs inside your
> 3GX.  There's clearance and space inside that could accomodate two
> SIMMs, providing you're good with a soldering iron around delicate
> circuitry (let me stress that you'll be wiring to signals that come
> right off the CPU, so be @#$%^@ careful).  If you're industrious, you
> might try your hand at low profile right handle SIMM sockets;
> otherwise, you'll need to put some good thought into a mounting
> strategy for the extra SIMMs.
>
> Now, before anyone wets themselves: THIS IS ALL THEORETICAL.  Don't
> try this if you have any doubts of your own abilities, or are scared
> of toasting your laptop.  There are lots of single mistakes you could
> make when working on hardware like this that could utterly trash your
> laptop.  So, DON'T DO IT unless you're prepared to take responsibility
> for your actions.  I have nothing to do with this or what you do.
>
> (ahem) Sorry.  You see a lot of that on the 'net.  Anyway.
>
> Amusing aside: I *loved* my 3GX, and often wondered why someone else
> hadn't done something like this before, once we realized how scarce
> the 128MB kits for the 3GX are.  Eventually, my impatience at swapping
> drove me to plan this project out, and I was ready for some
> exploratory surgery (I'm familiar with the inside of a 3GX, having
> opened it up in the past to fix a deteriorating keyboard (it turned
> out to be a slipping connector) and other things over recent years).
> Then, after I had read up on the CPU and learned something of common
> 72pin SIMM design, I got a new laptop from work.
>
> And that's when I realized why no one else had done this before.
>
> So, IN THEORY, this is all pretty straightforward (sheesh, it's just
> memory).  Chances are good that a couple people with the right skills
> could hook up and pull this off.  At the least, you could have a 3GX
> with four 32MB SIMMs; if you're insanely lucky, maybe more.  So, if
> you're good, and have the inclination and the time, think about it.
> It really can't be *that* hard.  And you'll be a hero.
>
> (Oh, great. Now I'm all nostaglic for "bat", my old 3GX... I think I
> might dust it off and boot it up this afternoon... ;)
>
> Cheers,
>
> // bob
>
> --
> // Bob Krzaczek, RIT Center for Imaging Science               <krz at cis.rit.edu>
>
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