In August of 2001, I got real gutsy. How, you ask? Well, I decided to take a geek-like plunge, and disassemble my Visor.
For the uninitiated, the “Visor” is a Palm Pilot clone, of sorts. The story goes like this: the three gurus responsible for the PalmOS and Palm Pilot, created their own company (Handspring) and set out to make a better Palm. I believe they did just that. You can read more about it at Handspring.
My first Visor (their flagship PalmOS product) was the Solo, which had 2MB of DRAM. Very small, in today’s large memory PDA machines. Still, for its time, it was great. I managed to keep from hitting the memory ceiling by keeping a streamlined tight ship, so to speak. I only installed the most necessary apps onto my Visor, and kept just a few games.
Nevertheless, it wasn’t long before I crept up to the 2MB limit of my handheld. And then last August, a certain module pushed me over the edge. I bought a VisorPhone, which is a GSM phone module for the Visor. It included the Blazer PalmOS internet browser and some other cool free apps. So I was at an impasse — either buy a new Visor with more memory (the next model up, the Deluxe, contains 8MB), or stop using these modules and their included software.
Obvious choice, right?
But I’m a hacker, dangit! Surely there’s something I can do about my memory dilemma! Well, there was something. With some scavenging on the net for tidbits of wisdom (or recklessness, depending on your persuasion), I dug up some interesting data. A really excellent source of help and discussion is VisorCentral.
There are a few companies out there that will take apart your 2MB Visor and replace the internal DRAM with 8MB DRAM chips, or IC’s (Integrated Circuits) as they’re called. A couple such companies are:
- STNE Corporation — they do mostly memory upgrades, and replacement color cases for Palm handhelds.
- GetHighTech — they offer a whole line of replacement internal circuit boards, memory upgrades, and miscellaneous parts.
While these two companies offer great services, the inner hacker in me was determined to give this a shot myself. Plus, being an electrical engineer and just handy enough with a soldering iron to be dangerous, I thought I couldn’t lose. So after some more digging on the internet (thank God for Google!), I found the following crucial information, a sort of cookbook on the guts of the Visor:
1. Here is a list of DRAM chips recommended for upgrades (Note that memory architecture is mostly standard across the manufacturer landscape for both pin-out and functions. This makes the device selection rather easy, as it’s really only a matter of distributor availability.):
- KM416V4104[ABC]S-L6 (Samsung)
- uPD42S65165G5-A60 (NEC)
- HM5165165LTT-6 (Hitachi)
- MT4LC4M16R6TG-6S (Micron)
- HY51VS65165CSLTC (Hyundai)
- TMS465169P (Texas Instruments)
I chose to go with the Micron DRAM, since Avnet (a distributor) had plenty that I could sample (ahh, the fringe benefits of the engineering world!).
2. The next step was to download both the 2MB and 8MB datasheets and determine what was really different between them.
But I found that it wasn’t as “easy” as replacing one chip with another. There’s a significant difference between a 2MB chip and an 8MB chip. Their pin-outs are not alike — close, but not quite. However, Handspring was smart in designing only one set of Visor circuit boards (PCBs) for both the Solo and the Deluxe. With a “jumper” component(s) and the appropriate DRAM chip, a Solo can become a Deluxe during the assembly stage. Therefore, if we know the correct jumper configuration, we can turn our Solo into a Deluxe.
In this case, the “jumper” components are zero ohm surface mount resistors. I removed the jumpers from positions R17, R21, R23, and R26 and put them in the vacant spots R16, R22, R24, and R25. Notice they are positioned in pairs: R16 & R17, R21 & R22, etc. However, the R19/R20 pair is not swapped. Relocating these jumpers allows the Visor to see the 8MB DRAM properly.
Here are two detailed pictures of my Visor internal boards and memory board.
Sadly, after all this work, in less than three months, my Visor Solo-turned-Deluxe was dead. In the most inopportune of times, right after a car accident, the Visor and attached VisorPhone would not turn on. Despite fresh batteries and frequent “soft,” “warm,” and “hard” resets, the Visor exhibited strange memory crashes and instability. I concluded that my tampering had finally taken its toll, like so much bad medicine.
“Oh well,” I said. “Easy come, easy go.” Besides, this was the perfect excuse to upgrade to a Platinum!
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