WIDCOMM Drivers Bug

  pincholas 18:05 08 Mar 2007

Hi! I have sent this email to Broadcom's support staff. Does anybody here notice this?
I would like to tell you about a possible BUG I believe there is in Widcomm/Broadcom Bluetooth software. As I am not english native speaker I'll try to express myself the best I can.

As you sure know there is a hidden file on Windows XP called IconCache.db located under "[drive]:\Documents and Settings\Username\Local Settings\Application Data". This file is the icon cache. Many advanced users feel the need to resize this cache to make it bigger and this is done, as it's documented by Microsoft, by adding or modifying this registry key:

HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Exp lorer\Max Cached Icons

The data type of "Max Cached Icons", as documented by Microsoft, must be REG_SZ and a recommended new value for it is "2000" or "2048" or whatever (depending on the sources you consult) but many prefer to go further and make it equal to 4000 or 8000 or whatever...

Also, there is another key that many users and tweak programs usually modify, this is

HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Exp lorer\AlwaysUnloadDLL

It's type is REG_SZ and it is said that if you make it equal to "1" the system will perform better.

Well, this said, let's have a look on what's happening when a user installs any WIDCOMM Bluetooth Driver under XP. Let me tell you that I have tested this with following equipment:

* IBM Thinkpad Notebook with Windows XP SP2 and integrated IBM Bluetooth III device.
* Homemade PC with Gigabyte motherboard, Windows XP SP2 and Belkin USB Bluetooth 2.0 dongle.
* DELL desktop computer Optiplex GX270 with Windows XP SP2 and Belkin USB Bluetooth 2.0 dongle / Billinton USB Bluetooth 1.1 dongle.

On each case I have used WIDCOMM drivers as provided by corresponding manufacturer. I have tested several version of WIDCOMM drivers being latest Belkin's v.5.1

After you install WIDCOMM drivers two resgitry keys are modified by your software, in my humble opinion, wrongly. The first is

HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Exp lorer\Max Cached Icons

because it's data type is changed to REG_DWORD and it's value set to 7D0 (hex) or 2000 (decimal). This modification causes IconCache.db not to work anymore. The icon cache gets useless. To prove it, delete the file iconcache.db and restart your computer. If the icon cache is working this file is recreated everytime you close your XP session but this time the file is not going to be recreated because of the wrong "Max Cached Icons" data type. This is going to impact severiously on Windows XP performance.

The other key created is

HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Exp lorer\AlwaysUnloadDLL\(default) = 1

this is "AlwaysUnloadDLL" is created as a sub-key not as a value. This is the old way of doing it. This is not going to impact on performance as the actual good value remains (if you have it set previously, but it is not created) under HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Exp lorer\AlwaysUnloadDLL.

It doesn't matter how many times you delete or modify this two keys as whenever you open explore.exe, they are going to be recreated/changed back again.

Uninstalling WIDCOMM bluetooth drivers stops modifying these keys so the system goes back to it's normal behaviour.


Best regards, Pincholas

  moorie- 20:57 08 Mar 2007

just out of interest are widcomm drivers windows certified

  Ashrich 22:12 08 Mar 2007

I am still using Widcomm bluetooth driver Widcomm Inc. 17/06/03 on XP sp2 and it works flawlessly , and is signed as well .


  pincholas 11:35 09 Mar 2007

umm... I don't get what you mean, moorie, why out of interest? I don't mind if a driver is certified or not, really, just if it works... and, there are two bluetooth stacks avaliable for Windows XP, one is a generic from Microsoft included in SP2, and the other is Widcomm's (Bradcom) one which is made avaliable from many (if not all) bluetooth hardware manufacturers with very little differences from one to another... so...

I'll try to test previous versions of Widcomm drivers (1.4.something or whatever)...

  pincholas 13:38 20 Mar 2007

In case anyone is interested on this problem, let me tell you what people from Widcomm have answered me:

First of all thanks for bringing this issue to light!!.

We have confirmed the problem and it will be fixed in the next release of the Bluetooth S/w.

Thanks again!!


BT Support


  maheath 15:02 16 Nov 2007

For anyone googling this problem with register key "Max Cached Icons" changing to DWORD (as I did) the answer is to update the WIDCOMM drives to latest version.

It can be done here:

click here

I just did it for my Belkin bluetooth USB device and now finally the register key is not changed for each boot. ;-)

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