Adobe Photoshop

Hello DACCLC. Let me tell you right off the bat that I'm far from an expert in the world of Photoshop or computers but i think i may be able to offer some insight here. -  Very rarely in our day to day desktop lives do most of us actually push the limits of our ram capacity. Even those with 4 gb of ram on a 32 bit OS really have to get busy multitasking with some fairly memory intensive processes before they begin to near their cap whereupon the limited ram becomes the "bottleneck" in the systems ability to stay efficient.  One of the few programs I use that acually manages to make good use of my ram happens to be Photoshop- Rendering large images in Photoshop has a way of slamming right up against that 4  gb limit with very little hesitation- Now, even if you have 8 or 16 gigs of ram on a 64x operating system, unless you are running 64X Photoshop you arent able to utilize that additional ram beyond the 4 gb mark due to the limitations of the 32 bit architecture. When that happens your system begins to use its page/swap file (virtual memory) on the hard drive instead of your ram. Accessing data from a hard disks page/swap file is amazingly sluggish compared to the rate your system achieves if its able to use your ram exclusively. Ram is all electronic processing as opposed to a standard hard drives method of reading and writing data by way of mechanical movement. Theres just no comparison when it comes to speed and so you find yourself waiting much longer to render a large file than you would have to if you were able to avoid defaulting to the use of that virtual memory on the hard disk. That being said, aside from those times when you would have the need to access more ram than 32 bit Photoshop can handle there isnt a huge speed advantage in using the 64 bit version.  From what i understand, the primary reason to keep 32 bit Photoshop in your toolset is because there are still a good number of plugins that have not been upgraded for 64 bit architecture and so if you want to have the speed advantages that come with the 64 bit and the notoriously complete functionality that 32 bit allows, you end up using both of them-  Unless you are in a crunch for disk space, i wouldnt hesitate to keep both versions installed just so you can make sure you have the right tool for the job when the time comes. As for Extendscript Toolkit I'm not personally experienced with it being that I primarily access only the most basic of functions in Photoshop. I'll have to assume for the time being that its likely Toolkit 5.5 builds upon the foundation laid by toolkit 5 or that you dont have complete functionality without having both at your disposal. Ill have to get educated on that one-    Here's a link to a page I found when I was trying to figure out if I needed both versions of Photoshop. Hope it gives you some of what you need. Good Luck!              http://blogs.adobe.com/jnack/2010/04/photoshop_cs5_64-bit_benchmarks.html