Windows 10 build 9838 (fbl_partner_eeap)

6.4.9838.0.fbl_partner_eeap.140914-0936
	Build of Windows 10
OS family	Windows NT
Version number	6.4
Build number	9838
Build revision	0
Architecture	x86, x64
Build lab	fbl_partner_eeap
Compiled on	2014-09-14
Expiration date
Timebomb	2015-04-15 (+213 days)
About dialog

Windows 10 build 9838 (fbl_partner_eeap) is a Technical Preview build of Windows 10, which was originally uploaded to BetaArchive on 17 January 2019 in the Japanese language. The x64 English checked/debug compile of this build was later shared on 4 November 2024. This build was originally released to Microsoft partners participating in the Ecosystem Engineering Access Program (EEAP), as indicated by the fbl_partner_eeap branch.

Editions and keys[edit | edit source]

Edition / SKU Name	Key
Core	334NH-RXG76-64THK-C7CKG-D3VPT
Professional	XHQ8N-C3MCJ-RQXB6-WCHYG-C9WKB
ProfessionalWMC (edition upgrade only)	GBFNG-2X3TC-8R27F-RMKYB-JK7QT

New features and changes[edit | edit source]

DockingController application[edit | edit source]

DockingController was used as an application for Surface tablets to switch between tablet mode and desktop mode.

Network icon on the notification taskbar[edit | edit source]

When the user clicks on the network icon on the taskbar in the notification area, the network settings open in the PC settings that do not depend on the Charms sidebar that were in Windows 8 and 8.1.

This may be a reference that a new network flyout which fits with the new design of Windows 10 was planned. An iteration of the new network flyout can be seen in build 10009, though a placeholder with the "Hello World" text was found in earlier builds. At this point in development though, no visible work has begun yet, as if the user changes it back to open a flyout, the Windows 8.1 flyout will open.

zSpartan[edit | edit source]

A reference to Project Spartan (would become Microsoft Edge later on) can be found in this build's Start Menu, however it points to an invalid location; the EXE and folder are nonexistant in this build. However, it reveals that the browser would be installed in the folder Microsoft.zSpartan_6.4.9838.0_x64__8wekyb3d8bbwe, and that its exe was called Spartan.exe.

Hidden features[edit | edit source]

Windows Update (Threshold)[edit | edit source]

It is possible to enable an early version of the Windows 10 Windows Update page by merging the following registry key:

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\WindowsUpdate\UX]
"IsMusUxEnabled"=dword:00000001

Displaying notifications at the top[edit | edit source]

The notifications are displayed at the bottom in this build by default, however it is possible to switch them to display at the top, like in Windows 8.1. To do this merge the following registry key:

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer]
"DisplayToastAtBottom"=dword:00000000

Modern IE[edit | edit source]

It is possible to run the Modern version of Internet Explorer by running the following PowerShell script:

$code = @"
using System;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
namespace Win8 {
   
   [ComImport, Guid("2e941141-7f97-4756-ba1d-9decde894a3d"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
   interface IApplicationActivationManager
   {
       IntPtr ActivateApplication([In] String appUserModelId, [In] String arguments, [In] UInt32 options, [Out] out UInt32 processId);
   }
 
[ComImport, Guid("45BA127D-10A8-46EA-8AB7-56EA9078943C")]//Application Activation Manager
   public class ApplicationActivationManager : IApplicationActivationManager
   {
       [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime)/*, PreserveSig*/]
       public extern IntPtr ActivateApplication([In] String appUserModelId, [In] String arguments, [In] UInt32 options, [Out] out UInt32 processId);
       
   }
   
}
"@
 
add-type -TypeDefinition $code
$appman = new-object Win8.ApplicationActivationManager
 
$appman.ActivateApplication("DefaultBrowser_NOPUBLISHERID!Microsoft.InternetExplorer.Default",$null,0,[ref]0)

Test UWP apps[edit | edit source]

This build's debug compile comes with many development UWP apps to test various functionality. These UWP apps are all a part of the Windows Communication apps (microsoft.windowscommunicationsapps), which in retail builds includes the Calendar, Mail and People apps.

The list of the debug apps in this build is as follows:

AddressWell Test App - tests the contact picker
AddressWellUT - unit test for the contact picker
Assert - reports assert failures for apps
AttachmentWellUT - unit test for the "attachment well" - possibly a file picker
Calendar - the regular Calendar app
Calendar Provider Test - lets the user perform various actions with the calendar, however crashes when the button to do the action is pressed
CalendarTest - Calendar app with mock data, doesn't require a sign in, and retains the user's added events
CalendarUT - unit test for the calendar
CalPlatUT - unit test for the calendar platform
CanvasUT - unit tests for the canvas
CommUT - unit tests for the communication platform
FontSelectorUT - unit test for the font selector
FromControlUT - unit test for the from control - possibly the "From" field in an e-mail client
IC Test - lets the user test how various communications controls react to various data
JxUT - unit tests for "Jx"
Mail - the regular Mail app. Doesn't seem to load
MailTest - Mail app with mock data
MailUT - unit tests for the Mail app
MenuArrowKeyHandlerUT - unit test for the menu arrow key handler - some sort of menu
People - People app with the ability to use mock data
PeopleUT - unit tests for the People
Picker Test - lets the user test the contact picker
PlatformUT - unit tests for the platform
Protocol Activation Test App - lets the user test launching the People app via various protocols
SendASmileUT - unit test for Send a Smile - possibly a feedback tool
ShareAnythingUT - unit test for Share Anything
ShareTargetTestApp - lets the user test sharing to an app. As it's a share target, content can be shared to this app from another app, where it pops up as a charm and shows information about the shared content
ShareTargetUT - unit tests for the share target
Sharing Test - lets the user test sharing to another app
Skype Test App - lets the user test Skype activation parameters
SyncUT - unit tests for syncing
TAEF Tailored Application Host Process - crashes on startup
TAEF Tailored Managed Application Host Process - crashes on startup
Test Harness - lets the user test various things relating to communication apps
TxUT - unit tests for "Tx"
Windows Live From Control Test App - lets the user test the "From" control
Windows Live Modern Canvas Test App - crashes on startup

Gallery[edit | edit source]

AddressWell Test App
Calendar Provider Test
CalendarTest
IC Test
MailTest
People (splash page)
People (main page with mock data)
Picker Test
Protocol Activation Test App
ShareTargetTestApp
ShareTargetTestApp being shared to from Sharing Test
Sharing Test
Skype Test App
Test Harness
Windows Live From Control Test App

Unit test app[edit | edit source]

The UI is the same between all the unit test apps. Only the unit tests themselves differ.

Unit test selection
Running unit tests
Results page

Bugs[edit | edit source]

Timebomb[edit | edit source]

Like other Windows 10 builds found in the fbl_partner_eeap branch, this build contains a non-functional timebomb and as a result can be installed on the current date.

Message boxes[edit | edit source]

Some message boxes, including the winver and "About Program" dialogs aren't properly resized. As a result, most of the buttons are missing.

Window thumbnail border color error[edit | edit source]

If window auto-colorization is enabled, the window thumbnail borders on the taskbar do not change color even after the wallpaper changes. This issue can be remedied by manually changing the window color through the Control Panel or restarting Windows.

Nvidia Driver/DWM Bug[edit | edit source]

This build like build 9834 has issues with certain Nvidia graphics drivers, causing DWM to crash, resulting in a black screen. A similar bug has been known to occur with certain AMD graphics drivers aswell.