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This posting is provided "AS IS" with no warranties, and confers no rights. The opinions expressed within are my own and should not be attributed to any other Individual, Company or the one I work for. I just happen to be a classic techie who is passionate about getting things to work as they should do (and are sometimes advertised and marketed as being able to?) and when I can I drop notes here to help others falling in to the same traps that I have fallen in to. If this has helped then please pass it on - if you feel that I have commented in error or disagree then please feel free to discuss with me either publically or privately? Cheers, Dave
Thin Clients, VDI and Linux integration from the front lines.... Raw and sometimes unedited notes based on my experiences with VMware, Thin Clients, Linux etc.
Update - I got a note from Stefan Vermeulen at http://www.printingsupport.com regarding some info from Brian Madden's forum and have posted it in the Comments - this includes the Registry tweak to increase the buffer to 16Mb per session.
I've been asked about multi-monitor support for Citrix ICA Sessions twice in the last week or so from two different sources so I thought it useful to pop this in as a post?
 
 
But this should give a very clear idea on what is possible? As you can see Dual Screens is really only the starting point?
A variety of issues surrounding the graphical display on the client device can be a result of memory setting per ICA session.

The maximum memory allowed for use as a buffer by each client connection on a MetaFrame server is 7,680,000 bytes. This maximum is a limit to the operating system and is not configurable. Up to the maximum amount of memory can be set in the Citrix Management Console at the farm or server level, but this also can be application-dependent. When the memory limit is exceeded in a seamless connection, the session is displayed in a fixed window with scroll bars. Seamless mode factors in the entire resolution of all monitors in a multi-monitor configuration. This chart shows various combinations of color and resolutions with various numbers of monitors and the amount of memory required for the ICA session.

Don't forget that this is a maximum limit "per session" and ICA will always try to utilize "session sharing" where ever possible to limit the number of licences consumed, so if you are trying to run two large display applications in Seamless mode - and they are sharing the session - then you will have to add together the memory required for each application and ensure that it doesn't exceed the max. 

Number of Monitors

Resolution

Color Depth

Memory Required

1

640 x 480

16 Colors

153,600

2

640 x 480

16 Colors

307,200

4

640 x 480

16 Colors

614,400

8

640 x 480

16 Colors

1,228,800

12

640 x 480

16 Colors

1,843,200

1

800 x 600

16 Colors

240,000

2

800 x 600

16 Colors

480,000

4

800 x 600

16 Colors

960,000

8

800 x 600

16 Colors

1,920,000

12

800 x 600

16 Colors

2,880,000

1

1024 x 768

16 Colors

393,216

2

1024 x 768

16 Colors

786,432

4

1024 x 768

16 Colors

1,572,864

8

1024 x 768

16 Colors

3,145,728

12

1024 x 768

16 Colors

4,718,592

1

1152 x 864

16 Colors

497,664

2

1152 x 864

16 Colors

995,328

4

1152 x 864

16 Colors

1,990,656

8

1152 x 864

16 Colors

3,981,312

12

1152 x 864

16 Colors

5,971,968

1

1280 x 1024

16 Colors

655,360

2

1280 x 1024

16 Colors

1,310,720

4

1280 x 1024

16 Colors

2,621,440

8

1280 x 1024

16 Colors

5,242,880

12

1280 x 1024

16 Colors

unsupported

1

1600 x 1200

16 Colors

960,000

2

1600 x 1200

16 Colors

1,920,000

4

1600 x 1200

16 Colors

3,840,000

8

1600 x 1200

16 Colors

7,680,000

12

1600 x 1200

16 Colors

unsupported

1

640 x 480

256 colors

307,200

2

640 x 480

256 colors

614,400

4

640 x 480

256 colors

1,228,800

8

640 x 480

256 colors

2,457,600

12

640 x 480

256 colors

3,686,400

1

800 x 600

256 colors

480,000

2

800 x 600

256 colors

960,000

4

800 x 600

256 colors

1,920,000

8

800 x 600

256 colors

3,840,000

12

800 x 600

256 colors

5,760,000

1

1024 x 768

256 colors

786,432

2

1024 x 768

256 colors

1,572,864

4

1024 x 768

256 colors

3,145,728

8

1024 x 768

256 colors

6,291,456

12

1024 x 768

256 colors

unsupported

1

1152 x 864

256 colors

995,328

2

1152 x 864

256 colors

1,990,656

4

1152 x 864

256 colors

3,981,312

8

1152 x 864

256 colors

unsupported

12

1152 x 864

256 colors

unsupported

1

1280 x 1024

256 colors

1,310,720

2

1280 x 1024

256 colors

2,621,440

4

1280 x 1024

256 colors

5,242,880

8

1280 x 1024

256 colors

unsupported

12

1280 x 1024

256 colors

unsupported

1

1600 x 1200

256 colors

1,920,000

2

1600 x 1200

256 colors

3,840,000

4

1600 x 1200

256 colors

7,680,000

8

1600 x 1200

256 colors

unsupported

12

1600 x 1200

256 colors

unsupported

1

640 x 480

16 bit color

614,400

2

640 x 480

16 bit color

1,228,800

4

640 x 480

16 bit color

2,457,600

8

640 x 480

16 bit color

4,915,200

12

640 x 480

16 bit color

7,372,800

1

800 x 600

16 bit color

960,000

2

800 x 600

16 bit color

1,920,000

4

800 x 600

16 bit color

3,840,000

8

800 x 600

16 bit color

7,680,000

12

800 x 600

16 bit color

unsupported

1

1024 x 768

16 bit color

1,572,864

2

1024 x 768

16 bit color

3,145,728

4

1024 x 768

16 bit color

6,291,456

8

1024 x 768

16 bit color

unsupported

12

1024 x 768

16 bit color

unsupported

1

1152 x 864

16 bit color

1,990,656

2

1152 x 864

16 bit color

3,981,312

4

1152 x 864

16 bit color

unsupported

8

1152 x 864

16 bit color

unsupported

12

1152 x 864

16 bit color

unsupported

1

1280 x 1024

16 bit color

2,621,440

2

1280 x 1024

16 bit color

5,242,880

4

1280 x 1024

16 bit color

unsupported

8

1280 x 1024

16 bit color

unsupported

12

1280 x 1024

16 bit color

unsupported

1

1600 x 1200

16 bit color

3,840,000

2

1600 x 1200

16 bit color

7,680,000

4

1600 x 1200

16 bit color

unsupported

8

1600 x 1200

16 bit color

unsupported

12

1600 x 1200

16 bit color

unsupported

1

640 x 480

24 bit color

921,600

2

640 x 480

24 bit color

1,843,200

4

640 x 480

24 bit color

3,686,400

8

640 x 480

24 bit color

7,372,800

12

640 x 480

24 bit color

unsupported

1

800 x 600

24 bit color

1,440,000

2

800 x 600

24 bit color

2,880,000

4

800 x 600

24 bit color

5,760,000

8

800 x 600

24 bit color

unsupported

12

800 x 600

24 bit color

unsupported

1

1024 x 768

24 bit color

2,359,296

2

1024 x 768

24 bit color

4,718,592

4

1024 x 768

24 bit color

unsupported

8

1024 x 768

24 bit color

unsupported

12

1024 x 768

24 bit color

unsupported

1

1152 x 864

24 bit color

2,985,984

2

1152 x 864

24 bit color

5,971,968

4

1152 x 864

24 bit color

unsupported

8

1152 x 864

24 bit color

unsupported

12

1152 x 864

24 bit color

unsupported

1

1280 x 1024

24 bit color

3,932,160

2

1280 x 1024

24 bit color

unsupported

4

1280 x 1024

24 bit color

unsupported

8

1280 x 1024

24 bit color

unsupported

12

1280 x 1024

24 bit color

unsupported

1

1600 x 1200

24 bit color

5,760,000

2

1600 x 1200

24 bit color

unsupported

4

1600 x 1200

24 bit color

unsupported

8

1600 x 1200

24 bit color

unsupported

12

1600 x 1200

24 bit color

unsupported

Posted on Wednesday, April 12, 2006 6:18 AM Citrix , IT Management , Real Cool Stuff , Microsoft Tips | Back to top


Comments on this post: Multi-monitor support for Citrix ICA Sessions - dual screens and the like

# re: Multi-monitor support for Citrix ICA Sessions - dual screens and the like
Requesting Gravatar...
Here is a quote from a post from Claudio overruling the 8mb limit on a 2k machine:
http://www.brianmadden.com/forum/tm.aspx?m=12743
Not sure if it's stull there today and if the total limit is still 16mb.
Left by Stefan Vermeulen on Apr 15, 2006 11:30 PM

# re: Multi-monitor support for Citrix ICA Sessions - dual screens and the like
Requesting Gravatar...
Thanks Stefan, I'll post that here as well just in case others find it useful?

Here's a story from Cláudio he once posted somewhere on how he did so you can use it for your own basis:


I have no idea if it is already fixed on Windows 2003 as none of my monitors can handle such resolutions.
And I have only one monitor so I cannot even try multi-monitor setups.
Although Citrix may allow you to do this, it is still limited on the resolution, color and number of sessions. This means a certain number
(memory allocated to the client) has a maximum value. What means the more resolution you have, you will not be able to have as many sessions as you want in high color for example.

More information:

"Citrix says with there Metaframe for W2k and 'Feature Release 1' upgrade, you can support 'multiple monitors' and 'greater colour resolution'. in actuality, the correct word is OR not AND ! Which means it can support 8 screens but only in 2-bit colour mode OR 1 screen at 16 million colours. The reason is due to the amount of memory that Citrix reserves for the video memory for the client.

By default, it is exactly 7680000, which is the maximum value the Citrix utility, "TWConfig", will accept. Now this value is out of 16Mb of total client session memory space. However, running the minimum 3 monitors for the traders at 16-bit requires 7,864,320 bytes, which is 184320 more than the default. So, we asked Citrix why their stuff didn't work. Finally after almost 2 months of playing email tag, they came back with a Registry entry change.

Here is what they sent us:

Win2k has a session pool limit of 16MB. The ICA pseudo frame buffer comes out of this session pool, and the maximum size of the frame buffer is specified by the registry value:

HKLM\System\Current Control Set\Control\TerminalServer\Wds\icawd\thin16\MaxLVBMem

The MaxLVBMem value specifies (in bytes) the maximum memory that thinwire will allocate for the frame buffer.
It can be modified using twconfig.exe; however, twconfig will not let you specify a value larger than 7680000 bytes.
The remaining 8.4 MB is taken up by other things that we have little or no control over (e.g. GDI itself, printer drivers, etc.).

Microsoft will not modify the 16 mb session limit before WHISTLER. Now, what we found out is that this key can be modified to other values. So when we need to support 4 monitors, we calculated the required memory in bytes (1280 x 1024 x 2 words (or 16-bit) x 4 monitors) and this equals 10,485,760. So, this was the value we entered into this key. And it worked. So, keep this in mind."

As I said it may be fixed with Windows 2003 but I could not try. Microsoft, if they read this post, can shed some light on this.

Cláudio Rodrigues, MVP
Windows 2000/NT Server
Terminal Services
Left by Dave Caddick on Apr 16, 2006 5:35 AM

# re: Multi-monitor support for Citrix ICA Sessions - dual screens and the like
Requesting Gravatar...
Hello
I have the same problem running 4 Monitors each 1280 x 1024 @ 16bit. I tried to fiend the key in registry of my WIN XP Prof OS but i couldn't find it. Could you please help me changing the memory value under WIN XP?
Left by Stefan on Sep 09, 2006 9:32 AM

# re: Multi-monitor support for Citrix ICA Sessions - dual screens and the like
Requesting Gravatar...
I have the same problem as Stefan, I tried searching everywhere in the registry for a simliar entry but can't find it. I am running Citrix Presentation Server Client 10.100.55836 Please provide information about how to add this registry entry or some other solution. Thanks a lot! :-)
Left by Kevin on Dec 05, 2007 11:40 PM

# re: Multi-monitor support for Citrix ICA Sessions - dual screens and the like
Requesting Gravatar...
The registry information can be found on the server and not on the client. You must edit the registry on the server.
Left by Kevin on Jan 03, 2008 7:34 AM

# re: Multi-monitor support for Citrix ICA Sessions - dual screens and the like
Requesting Gravatar...
Sorry chaps, I'm not monitoring this blog as closely as I once was - Kevin is absolutely correct, these tuning details for the registry will be on the Citrix Server

Dave
Left by David Caddick on Jan 03, 2008 8:30 AM

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