Upgrade Type 5 Mice from 1200bps to 4800

James Lockwood has a Modification Guide to 'upgrade' Type 5 Mice from 1200bps to 4800.

James writes:
Type-5 opticals and mechanicals can both be upgraded to 4800bps.

Here's a modification guide I came up with last year:

Sun mice are both good and bad. Good, because they're generally very well made and have an excellent feel (I prefer the opticals myself). Bad, because they run at a slow serial speed (1200bps). This makes mouse movement somewhat "jumpy".

Due to the way that mouse movement is encoded on a Sun, you can only get a maximum of 24 positional or button updates per second. This doesn't sound so bad until you realize that you are getting a new position less than half as often as you are updating the screen, and you are looking at a minimum of 40ms latency for any mouse action at all. Move nearly any Sun mouse rapidly from side to side, and you get a very jumpy response. The same problem is noticeable to a lesser degree when scrolling or moving windows.

The good news is that Sun, in their considerable foresight, made it possible for all type-5 mice to run at a faster serial speed (4800bps). This gives you 96 updates per second with 10ms latency which gives a much better mouse feel (and better performance from interactive RT processes such as 3D visualization or games). You need Solaris 2.3 or above to take advantage of faster mice speeds.

Anyways, here's a brief guide to "upgrading" your Sun type-5 mouse. No warranty expressed or implied, if you screw up and toast your E6500/Elite3D that you're using for 3D visualization of weather data I will disavow all knowledge of this message. This post will self-destruct in 5 seconds...

Anyways, there are two different versions of the type-5 mouse. I'll discuss the ball mice (optomechanicals) first:

If you've got a mouse that's part number 370-1586-01, congratulations! You have an extremely rare piece of Sun history, that will doubtless be worth as much as $15 in another decade. These were the only 4800bps mice produced by Sun (for the Voyager). Lord only knows what they were thinking at the time.

Part numbers 370-1586-02 and -03 are the most common versions. These are fairly easy to modify as follows:

Remove the mouse ball. Disassemble the mouse by removing the 3 bottom screws and remove the top cover. Unplug the circuit board from the cable and flip the board over.

Using either a soldering iron or a pair of cutters, remove the zero-ohm resistor at "R3" (near the mouse ball). Connect the solder pads at "R2" (in one corner of the board) using either a blob of solder or a wire whisker. If the jumper at "W9" (next to R2) is missing (usually is on -03 mice, isn't on -02 mice), short that one as well (you can't just use a blob of solder here as another wire runs between the terminals). Installation is the reverse of removal.

For opticals (370-1398 tested, no idea on any other):

Remove the felt pads on the bottom, exposing the screws and plastic tabs at the top. Remove the screws and pop the tabs out using a flat-bladed screwdriver. Remove the top cover. _Gently_ unplug the circuit board from the flex-cable that runs to the optics, I find that a pair of non-crushing needle-nose pliers and a lot of patience is good here. Extract the board and flip it upside-down (but don't disconnect the cable that comes out of the mouse, it's a pain to get back on right).

Join the solder pads at one corner near the main chip labeled "JP2" with a small wire. Reassemble, being careful to get the flex-cable back in all the way without breaking it. Also make sure to route the main cable that runs out of the mouse correctly, if you don't lay it in the proper channel then you can cause binding of the middle button.

This is it. Plug it in and move the mouse around. Pretty smooth, eh? To confirm that you are running at 4800bps, run:

% stty /dev/mouse speed 4800 baud; -parity ...

I hope this helps people, it's a cheap upgrade that makes a terrific improvement. Once you've done it, it's hard to go back.