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#1 2016-01-16 18:06:07

MacOS Plus
Registered: 2015-12-09
Posts: 110

Musings about modding a Powerbook Duo 2300c.

Years ago I bought a second-hand Powerbook Duo 2300c and a DuoDock II in separate eBay auctions.  The Powerbook was foolishly shipped to me in a simple bubble-mailer envelope, which quite predictably led to the LCD panel getting broken in transit.  Cosmetically it is fine and also it functions perfectly well in the dock.  Obviously this was a disappointment though and soon the project got pushed aside by other things.

  I just now managed to get another Powerbook so I can make one complete good one out of both, plus I end up with quite a few spare parts.  Knowing that I have two functional motherboards got me thinking about tinkering with one of them to see if there are any improvements that can be made.  If I wreck the second one in the process I still have a good one.

A. CPU upgrade:

  The first thing I was wondering about is replacing the CPU chip.  Thankfully it's a soldered pin-mount rather than a ball-grid which makes this feasible with the tools and supplies I have at hand.  (240 pins is no fun, but certainly doable given that I've already swapped 160-pin chips before.)  The chip is a 100MHz first-generation 603e, model code XPC603EFE100MF.  This very limited series is supposed to have a 133MHz variant that only differs in that it uses more power.  This is the only option because one of the supply voltages changes in the next revision.  See the following link for extensive details of all the variants of PowerPC chip from 601 through 750:

  The 603e uses two multipliers to set its internal speed.  The first controls the internal bus speed versus the external bus speed (1.5x for a 50MHz internal bus in the stock PB).  The second controls the main processor speed versus its internal bus speed (2x 50MHz for a 100MHz speed in the stock PB).  There are four pins that control the multipliers, one pair for the bus speed and one pair for the CPU speed.  Page 24 of the following PDF file shows the configuration chart: … 603EEC.pdf

  Setting the correct multiplier for a 133MHz replacement chip should be a breeze.  This is far better than trying to overclock the stock CPU or the logic board bus speed because either is likely to cause random issues or fully non-functional periferal devices.  One thing I need to sort out is whether or not there is any difference between part numbers beginning with "X" or "M".  The stock PB chip starts with "X" in mine.  The following eBay listing looks like what I need but starts with "M": … 487218a8b6

  There's no way I'm spending that much money for one, but it's the only sales listing I could find.

B. Hard drive replacement:

  I assume that an PATA SSD is out of the question because of ATA mode limitations.  This could be a brand issue only but the only way to know for sure is to test it.  I've had horrendous luck with one model of Transcend SSD in later powerbooks already, but Kingspec worked without issue in my TiBooks.  I could go with Compact Flash storage and an adapter but cost and speed may not be all that great by comparison.  I also have to worry about the need for third-party disk drivers for non-Apple drives.

  One possible bonus with the CF/adapter route is that it leaves loads of space in the drive-mount location.  Given that these logic boards have both ATA and SCSI available for internal drives (such that a 2300c board could be fit into an older Duo as an upgrade), conceivably you could actually install BOTH an ATA and SCSI-connected CF/adapter combo in the available space and end up with a dual-drive PB!  I would simply need to source the SCSI ribbon cable to add in.  If an SSD works on the ATA there may still be enough space to have a CF/adapter combo present on the other bus too rather than two CFs.

C. Video RAM:

  It's really sad that they couldn't put enough VRAM on-board to give you full resolution at the highest color depth setting.  Probably they simply ran out of space on the crush-loaded logic board because there are simply too many devices.  Two drive controllers and two screen drivers simply ate all the space (and possibly the power).  What I'm not certain of is whether or not the video controller is capable of addressing more VRAM than is physically present.  I'm wondering if doubling-up the VRAM with more chips wired in together would actually allow double the VRAM.  There could be an addressing limit, a physical trace-count limit, or even a rom or driver-coded limit that would prevent this from working.  I don't know enough about the inner workings of any of these things to hazard a guess.  Perhaps someone more versed in the area could comment.

D. System RAM:

  It always bugged me that the maximum RAM count was 56MB, not because I want more per se, but because it doesn't make sense as a binary number multiple typical of just about any other maximum in computer architecture - You'd think it should be 64MB.  This makes me wonder, similar to the example above in the VRAM section, can the controller address 16MB of on-board RAM but Apple could only fit 8MB physically in the space available?  System Profiler indicates that the on-board and expansion RAM are two distinctly separated banks.  The on-board RAM may therefore not have to be any particular size in relation to the expansion RAM.  (Possibly it could be 4MB or zero, even.)  The chips used are identical to the ones on the 48-meg ram expansion module.  That module uses some full-size chips but also some that are very thin in order to pack enough of them into the available space.  Perhaps doubling-up the RAM with thinner chips wired in together would be a possible workaround, similar to what I suggested in the VRAM example.  Again, I'm not versed-enough in this depth of knowledge quite, so I would appreciate some input.

  On a related note, I have a 48MB expansion module as I mentioned, but also a 24MB one.  If the 48MB won't play ball with a larger RAM on the logic board then I can at least see what happens with the 24mb one present.  I also noticed that the 24MB one has open solder pads for another 8MB set of chips, so if anything at all gets done out of all my musings it will be increasing this module to 32mb because at least that is guaranteed to work.  Either that or the thin chips on the 24MB module can be lifted to test expansion of the on-board RAM if I can't find any others in my junk pile that are at least 70ns.

  In summary, none of these possible changes, with the possible exception of the drive upgrade, will make much difference to the system performance.  I'm well aware of that but I'm more interested from the "because I can" standpoint.  I'd be happy if I could just marginally improve the awful window scroll speed.  (Is it really that slow?!?)

Last edited by MacOS Plus (2016-01-16 18:19:58)


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