Slow by modern standards, being pre-Nehalem, yes. But not 32-bit, the X61s tops out at a 1.8Ghz c2d L7700, which is 64-bit:

https://ark.intel.com/content/www/us/en/ark/products/32243/i...

  Intel® Turbo Boost Technology: No
  Intel® Hyper-Threading Technology: No
  Intel® Virtualization Technology (VT-x): Yes
  Intel® 64: Yes
  Instruction Set: 64-bit
  Enhanced Intel SpeedStep® Technology: Yes
  Intel® Demand Based Switching: No