Is this the SFF variant of the HP G1? If so, you need to look for a "low profile" GPU.
Secondly, if the machine is SFF, you'll need to make sure there's no additional power connectors on the GPU (because the stock PSU in your machine won't have the requisite connectors).
In looking at the specs for the HP ProDesk 600 G1, I see that the "stock" dGPU choices all max out at 35W TDP. Sometimes these SFF mobos can't output the "standard" 75W from the x16 slot and are limited to 35W instead. Something to be aware of. I don't see a 35W TDP limitation explicitly stated on the spec sheet though.
Is this the SFF variant of the HP G1? If so, you need to look for a "low profile" GPU.
Secondly, if the machine is SFF, you'll need to make sure there's no additional power connectors on the GPU (because the stock PSU in your machine won't have the requisite connectors).
In looking at the specs for the HP ProDesk 600 G1, I see that the "stock" dGPU choices all max out at 35W TDP. Sometimes these SFF mobos can't output the "standard" 75W from the x16 slot and are limited to 35W instead. Something to be aware of. I don't see a 35W TDP limitation explicitly stated on the spec sheet though.