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After looking at all the available info I'd like to propose a possible solution to the low FPS and spiking issues many have been experiencing. This solution is provided assuming that you system was running GW just fine before the 'update'. First I'd like to review the usual suspects.
Sound update. I believe this to be a non-issue as many, including myself, have run the -nosound switch and still receive the same poor performance.
Graphics update. Nothing added by Anet(whether it be polys or textures) should be creating the 'spike' effects with the graphical power available in today's systems. Most of the players posting these issues have great specs, more than enough power to run GW. Another non-issue.
Network code. Anet has not stated that any changes were made to the network code. At this point another non-issue.
Memory management. Anet removed the switch -heapsize for the Apr.5 update. This switch allowed users to allocate memory specifcally for GW. With this knowledge I started to watch my hard drive activity during these 'spikes'. As it was, all spikes were concurrent with hard drive activity. It would appear that the constant swapping of data during gaming was creating the 'lag spikes' I was experiencing.
This procedure helped the FPS and spike problem on my system and my girlfriends. No only that, it was faster than ever. I would like to disclaimer that this involves entering and changing the registry. I take no resonsiblity for your own errors, advice given, etc...
I have my pagefile(swapfile) set to a single size(min/max)... 1024mb, therefore the pagefile will not resize while playing GW or using any other program for that matter. Here's how to change the pagefile size...
Right click on 'My Computer' to bring up a small pop-up menu. On this menu, click on 'Properties' to bring up the System Properties window. Click on the 'Advanced' tab. In the Performance window, click on the 'Settings' button. Click on the 'Advanced' tab on the top. In the Virtual memory window, click on the 'Change' button. Select the 'Custom size' option. Setting the 'Initial size' and 'Maximum size' to the same value. I use 1024mb, more than enough to run GW on systems with 512mb+ memory. Click 'Ok', then 'Ok' and reboot.
Tip... Before I defrag I select 0/0 for the 'Initial size' and 'Maximum size' and then select 'No Paging file'. This allows the area on your your hard drive which was used by your pagefile to be defragged as it is no longer there. After the defrag I reboot and reactivate the pagefile(as above) to it's previous state on a freshly defragged drive
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The next two registry settings change the way XP handles file system cache, driver and code paging. To find and alter these keys...
Click on 'Start', than 'Run', then type regedit, then 'Ok'.(If you have no experience with 'regedit', do some research first as you can damage your registry if you delete/change/move a crucial entry)
Go to to the following key..
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Contro l\Session Manager\Memory Management
The settings we are looking for are...
DisablePagingExecutive and LargeSystemCache.
DisablePagingExecutive - double click the entry and set the value data to 0 (it may be already set to 0 as it is XP's default setting). This will allow the kernal driver and code to reside in the pagefile when not in use.
LargeSystemCache - double click the entry and set the value data to 1. This will allow XP to keep large amounts of data in memory instead of paging it from the hard drive.
After applying these changes, reboot.
Run GW and let me know.
If this does not help, then I apologize for wasting your time and getting your hopes up.
Cheers.