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This article is related to the Palmtops HP 100LX, 200LX and 1000CX, partially to the OmniGo 700LX. The 95LX cannot be upgraded in the way described here.
See also: Tutorial: Disassembly of a 200LX
If you are interested to have your Palmtop upgraded by an expert, please have a look at my HP Palmtop related products page.
The double speed upgrade is a way to make the HP Palmtop faster. It will double the CPU frequency and thus approximately double CPU-intensive tasks. Also access to other hardware components in the Palmtop is done with higher speed, as the hardware components allow this. So, the screen updates are quicker with a doublespeed upgrade, for example.
The upgrade is done by replacing the original quartz crystal which clocks the CPU by one which is twice as fast. The original crystal is abt. 15.8 MHz, which lets the CPU work at a speed of about 8 MHz. The upgrade crystal should have exactly 31.673 MHz, which speeds the palmtop up to about 16 MHz. Such a crystal can be bought from Times2Tech. A 32 MHz (or even faster) crystal could also be used, but this may lead to some problems with time-critical hardware components, such as the PCMCIA port and the communication ports (serial and IR).
Position of the quartz crystal on the motherboard:
An original single speed quartz there is labeled 158 CP52.
The double speed quartz by Times2Tech is labeled F31.673.
If the quartz is placed accordingly, you may see if you have a single or double speed quartz installed by looking through the backup battery slot:
You can easily check, if you have a speed upgrade installed, if you are unsure:
First, close all applications and save all open files. You need to reboot in the next step.
Switch the palmtop off.
Press ESC-ON. This shuts down the running system session and brings you into a self-test routine.
If you can not read the screen, it is double speed for sure.
Else: Select "Timers" and hit Enter. The timer test runs.
If the timer is in the 20800 range or so, the LX is double speed, if in the 10700-10914 then single (original) speed.
Afterwards, reboot the palmtop by pressing Ctrl-Alt-Del.
To make everything work with the upgrade, a driver is needed. For the Times2Tech upgrade, it is the spd31.sys or spd31.exe driver, which comes with the upgrade (or download it here).
If you use a 32.0 MHz or a 31.0 MHz crystal, you need the clkup32 or clkup31 driver. For crystals with speeds faster than that there is no special driver (and due to the risks of making the palmtop inoperational, it is not recommended to use such crystals).
There is another driver called clockup (download clockup.lzh here), which comes with source code and has a system clock correction feature. Maybe it can be used with exotical crystals. If you buy a crystal not sold by Times2Tech, make sure it is no overtone (harmonic) quarz, but the nominal speed is the main frequency. Otherwise you would need to filter out the (slower) main frequency.
If another quartz than the exact doublespeed 31.673 MHz quartz (made by Times2Tech) is used, this may cause slight problems due to non-exact timings. For example it may be that the serial port / IR port does not work correctly anymore at higher baud rates. This usually does not happen, if you use the correct driver, but I have heard of cases where there are problems. It seems to depend on the specific hardware due to component value tolerances. If the quartz has been installed professionally, it usually is no problem to replace it by the original 15.8 MHz quartz again in case there are problems with the doublespeed upgrade.