I believed that the PNY memory was high density because PNY does not seem to
make any low density RAM.
I doubt that the K-Byte memory that you list is low density. PC-100 does not
guarantee that.
K-Byte maintains a configurator. For the Optiplex GX1, it lists:
http://www.kbytememory.com/configurator/upg.pl?man_id=31&model=12733
It looks like the part number you'd need is 311-0717-KBT. The part number
from the Tiger link that you provide is for KB256-100.
Low density memory is from an older technology, so it will probably cost
more per megabyte than the (incompatible) high density version. You may have
trouble finding it from an online dealer that isn't a specialty house, so
www.crucial.com may be your safest source.
I have no connection with Crucial, or their parent company, Micron. I have
done business with them exactly once, buying - you guessed it! - a couple of
low-density 256 MB SDRAM DIMMs to upgrade my old Soyo 6BA+IV system (440BX
chipset, like the GX1) so that I could install Windows XP. (This, after
having some high density DIMMs not work. Incidentally, the Crucial DIMMs
were PC133.)
This doesn't seem to be what you wish to hear, but I can't help that.
If you wish to waste time, proceed to order an inexpensive high-density 256
MB stick. Your PC may even boot with it installed. However, if you run a
memory checking utility (or just run an application that really uses the
extra RAM), the new memory will fail. I believe that you won't damage
anything, but there will be memory errors.