Debian buster installation with 32-bit RTAI Source

I'd disagree.
No I wasn't suggesting a parallel uses serial data. Or each bit was handled & written individually. Maybe 6 parallel streams of serial data would have been more apt.
I guess when you say "A port at a specific memory address" you actually mean a location, generally a port is considered to be a physical connection to the outside world, unless of course we are talking networking.
I guess it could be described as a temporary holding area ?
But if take each bit in isolation, say the bit that is driving the step signal for the X axis and view it on a scope it will be seen as serial data, not any identifiable protocol but a stream of serial data.
Now look at X-Step, X-Dir, Y-Step, Y-Dir, Z-Step & Z-Dir on a logic analyser and you will see 6 streams of serial data.
It was more of a broad description of what is happening. Just to drive home the need for everything to be in sync. We lose that sync (regularity) and parts end up as scrap.

A good platform, unfortunately a little underpowered and only supported by Machine Kit is the Beagle Bone Black, as it has 2 separate microcontrollers that run independent of the OS that can be used to generate the hardware signals for the steppers. I used one for about a year, but for various reasons I changed to Linuxcnc & Mesa connected Ethernet solution.
But we still get back to the need for regular latency/low jitter.

I think the best solution we have, that allows a broader scope of machines is the solution we have with the Mesa FPGA cards. Linuxcnc still generates the timing data but the "bit twiddling" is handled by an FPGA.........A very broad and basic understanding of what happens. Rather than having a base thread of 25us and a Servo thread of 1ms we just need the servo thread. And the system can tolerate a greater latency..up to a point.
Whilst it may be a more expensive option initially, I believe that (especially the ethernet solution) has some "future proof" as I can't see the humble Ethernet port disappearing too soon....tho B Gates did say that 640k RAM was more than enough.

Is there definitely no way to run a 64-bit kernel on your machine?

As far as I know RTAI is now 64-bit only, so I did not try to create a 32 bit RTAI kernel.

But if you can run 64 bits then Buster RTAI kernel and LinuxCNC packages exist for installation through the package manager.

Looks like old mate is running an old 32 bit P4.

Hello Andy,
That is the very first thing I tried. The live CD would not even load. I did manage to get wheezy and and precise to load but they both hung as soon as I enabled "lapic" whilst buster 32 bit worked perfectly. BTW I had to change the latency base-period to great than 60uS in order for it to not load 10uS into the counter.

@Beagle
It must be age that is making me not want to discard this laptop. Maybe I do not want the same end result?

PS.
I've just ran a latency test using your LinuxCNC 2.8 Live ISO on my Acer 8943G laptop that has
Intel I7-740MQM Processor
8GB of DDR3 DRAM
ATI HD5850 Video
SSD 1TB

The numbers appears to be much worst Max 1mS timer 1.969mS Max 25uS timer 141uS. All my tests are with wi-fi disabled. and no other activity.

Same test on 32-bit system except base-time set to 66.666uS for it to run
1.154mS
190uS

There is awesome similarity between film recording and CNC machining. If your timing is off, in one you have a piece of scrap film in the other you have a piece of scrap..

Here's a sample quick test of my T530 with wifi on with a 35000 base thread. With Firefox open whilst reading this thread.
Not really a full test but it goes to show that a lesser spec machine can give better results.
This is with the same kernel that I supply on the Mint 19.2 Linuxcnc ISO the 19.3 ISO has a slightly later version on the RT_PREEMPT patch. Just for completeness the BIOS options have been set to the lowest power saving options.



Same machine with CPU #1 isolated