What OS/ISO Pair with What CPU?

I have a couple old/older PC to repurpose for LinuxCNC. I'm getting poor latency number from one PC running the Stretch ISO/image I pulled form a tread on this forum. So I wonder If I should go back to Wheezy and tune that or try a different PC, so many options!

My question is, what is the general rule of thumb for what OS version best pairs with what range of CPU/hardware.

How old and what are the specs of the PCs in question? Older hardware is more likely to work better with the older OS. But if the PC is really old and pathetic, it might just be time to let it go.

the PREEMPT_RT kernel in the stretch ISO in my experience does not work well on old 32 bit hardware. Latency was so bad I bought a new machine.

32 bit hardware is going to be at least 10 years old so that s pretty old...
(Pentium 4 vintage)

core and older ( before core2 ) = RTAI
core2duo and newer = PreemptRT
for core2duo both work nearly the same.

Todd Zuercher wrote: How old and what are the specs of the PCs in question? Older hardware is more likely to work better with the older OS. But if the PC is really old and pathetic, it might just be time to let it go.

Gateway E-4200 ( 500MHz Intel Pentium III)
Dell 530 (Intel Core 2 Duo / Pentium Dual-Core / Celeron 400 Socket 939, 2MB)
Dell 1520 Laptop (Intel Core 2 Duo Socket 939, 2MB)
HP 1st gen i7 desktop (I prefer not to use this one, already allocated for another project.)
Raspberry Pi 3

I was hoping to re-purpose one of the above.

That does not look right ( 2 and 3 ), but they can be used with Wheezy for sure, the 1 one will need a bit of searching to find the 8.04 or 10.04 version of Linuxcnc ( it was named EMC2 at that time ).

The P3 probably isn't worth the effort.

The Dell 530 might not be a bad choice,
Use rtai (wheezy) if you want to use a parallel port interface. The stretch one may be a good choice for other hardware interfaces.

The laptop probably isn't a good option.

Todd Zuercher wrote: The Dell 530 might not be a bad choice,
Use rtai (wheezy) if you want to use a parallel port interface. The stretch one may be a good choice for other hardware interfaces.

The 530 is my preference over Ethernet to a 7i96e card.

I could use the i7 if I swap HDD. I fear if I dual boot I'll mess something up, been known to happen .

I'm going to give the Dell 530 Intel Core 2 Duo Socket 939, 2MB another try. I still have the Wheezy ISO I can load.

Do I automatically get RTAI or Prempt_RT loading the Wheezy ISO from the Wiki? Other than updating LinuxCNC I should leave the OS alone and don't update it?

Any pointers on what to update, what not to?