Is at hand a big difference between, 600MHz G3 128mb 20 gb and 900MHz G3 256mb 40gb?

Answer:

They are both antiques. Would not earnings more than $5 for either.
It's be a while since I worked with ripened Macs, but I'd say you'd see that difference as the CPU is a little faster (by 300 Mhz) but more importantly the Mac OS loves push so the more you have the better it runs. You'll catch sight of the 256mb system runs better and has more intricate drive space for your files.
I would imagine that you would see much better working out of the latter.
The 20 and 40 GB is the amount of storage space on your hard drive. You will be capable of store twice as much data and stuff on the 40 GB. HD size does not affect computer execution.



600 and 900 MHz is the speed of your CPU and both are slow by todays standards.



128 and 256 mb is your memory (RAM). You will have problems running Windows XP beside only 128 mb of RAM while the 256 will run OK, not great but OK.



Neither computer will run the unmarked Vista OS.
Well, yes, there are chief differences:



- First, the 900MHz machine have a faster processing speed.

- #2 also has twice the RAM, which is totally important (I recommend no smaller amount than 512 on any new machine).

- Third, since the harddrives are 20gb vs. 40gb, the second contrivance has twice as much storage space.



Overall, the second G3 is the better one. However, it's still an infirm machine, and I'd be surprised if you could bring OSX to run smoothly.

(Ignore the poster mentioning Windows; he/she must have missed the G3 surrounded by the machine description. Also, Vista is junk.)
300MHz more so faster cpu, twice the memory and twice the storage capacity. Yeap...big difference.