Technical Support Coordinator, BAKA Computers
Apple shamefacedly admitted last week that its introductory materials and data sheets for the Quadra 610 incorrectly stated that all Quadra 610s have a floating point unit (FPU). In fact, Apple changed the configuration of the Quadra 610 8/160 at the last minute; it includes a 68LC040 processor instead of a full 68040, and therefore lacks an FPU.
Both other Quadra 610 configurations (the 8/230 and 8/230 CD) provide the FPU within the 68040 processor, as do all configurations of the Quadra 660AV. All configurations of Quadra 610 include built-in Ethernet.
Although Apple doesn't offer an FPU upgrade for the Quadra 610, third parties have sold full 20 MHz 68040 chips for the purpose of upgrading the Centris 610. It should similarly be possible to obtain a 25 MHz Motorola 68040 chip to replace the 68LC040 in the Quadra 610, but users should understand that this isn't an Apple-approved or Apple-endorsed approach [and if I remember correctly, it's expensive too -Adam]. Users who require the FPU capability should purchase a Quadra 610 with a full 68040 or a higher-end Quadra.