Multi-monitor support for Citrix ICA Sessions

Multi-monitor support for Citrix ICA Sessions - dual screens and the like

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?

Using Multiple Monitors with Seamless Windows

Seamless Windows Problem with NVidia Dual Screen Client

But this should give a very clear idea on what is possible? As you can see Dual Screens is really only the starting point?

Graphical Display Issues with One or More Monitors

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

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# re: Multi-monitor support for Citrix ICA Sessions - dual screens and the like 4/15/2006 11:30 PM Stefan Vermeulen

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.

# re: Multi-monitor support for Citrix ICA Sessions - dual screens and the like 4/16/2006 5:35 AM Dave Caddick

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

# re: Multi-monitor support for Citrix ICA Sessions - dual screens and the like 9/9/2006 9:32 AM Stefan

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?

# re: Multi-monitor support for Citrix ICA Sessions - dual screens and the like 12/5/2007 11:40 PM Kevin

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! :-)

# re: Multi-monitor support for Citrix ICA Sessions - dual screens and the like 1/3/2008 7:34 AM Kevin

The registry information can be found on the server and not on the client. You must edit the registry on the server.

# re: Multi-monitor support for Citrix ICA Sessions - dual screens and the like 1/3/2008 8:30 AM David Caddick

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

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