i have been using Ryzen for over a year now and it works nicely here

I wouldn't be concerned at all to use a Ryzen CPU with Slackware. There are only a few issues to worry about.
1: 14.2 can't handle the onboard Vega graphics on the CPU's that have it.
2: The installer for 14.2 can't handle NVME drives. Once installed using a modified installation script things work just fine.
3: I recommend running a 4.14.x or newer kernel if attempting to run Slackware 14.2. 4.4.x worked for me, but there is no CPU temp monitoring and some people have reported instability. Some AM4 motherboards also may have onboard Ethernet or audio controller that isn't supported by 4.4.x.
4: Some people are still having some issues with onboard graphics and -current.
5: Avoid early 1000 series Ryzen CPU's with a build date of 1724 (Week 24 of 2017) or earlier, they tend to have stability issues when occupying all cores simultaneously. I thought all of these were long gone from stores, but I spotted some very recently when I picked up a 1700X on sale for $149.99 USD.

You just need to update your BIOS and it should be fine with Ryzen.
In fact, i just upgraded my BIOS few days ago to the latest version for my mobo and it's working smoother here

I do still run into occasional low usage lockups (if I don't use the system for some time with nothing major running) with my 1800x with the latest BIOS if I don't have the rcu_nocbs=0-15 in my kernel appends line, but otherwise, mine has been rock solid.

Otherwise, akimmet has it pretty well covered for Slackware and Ryzen. I hope to be upgrading my media center PC to a Ryzen 3 2200G in the next few months and will have to put -current on it, since the graphics won't be support in 14.2 without a major overhaul of stock packages.

I had some trouble with this, but with a catch, more on the catch later.

MSI 470 'gaming' plus. Its onboard Ethernet is an RTL8111/8168/8411 and the kernel kept loading the module for r8169, which made my card unusable...
...or so I thought!

Here's my caveat. I did a hardware upgrade after almost 10 years, so I basically replaced everything.
Thing is, I didn't change "/etc/udev/rules.d/70-persistent-net.rules" to reflect the new hardware, so Slackware was still looking for my, now unavailable, old ethernet card as eth0.

In the end, both the r8169 driver and the one from realtek work, it seems.
Right now I am running the realtek one, but I do think the r8169, which I have blacklisted now, since I use the realtek one, will still work, at full speed too.
I think I had to change a bios setting, something about legacy ethernet or something, though, for that to work.

The realtek driver I use is this one https://github.com/mtorromeo/r8168

So yeah. If things are bad, possibly look into this.
Of course if you do go with the realtek one then you will have to recompile it when you upgrade kernels, etc.

I realize that this post is not the most, uh, straightforward or 'solid', but I have to admit that network stuff on *nix is a magical land of voodoo to me.
So I cannot give a more expert sounding solution.

I just know that this worked for me.

How to obtain that information when ordering online? Only the SKU number is provided.

I was thinking about this CPU:

AMD RYZEN 5 1600 6-Core

Thanks for this
I will try to add the same parameters to my grub since i saw same symptoms here

I wouldn't be sure, but the notes at the bottom are copyrighted 2017, where the newer version is copyrighted 2018.

Don

As far as I know, there's no way to tell when ordering. As far as AMD and sellers are concerned, they're the exact same product. Once you get the CPU in hand, that's when you can check.

I think that won't change. It's just the marketing information AMD provided to sellers for the product.

Edit: my bad, looks like there are still some old chips around based on earlier postings. Sorry.

Since I had the opportunity to do so, I have tried Slackware-current on a system with a Ryzen 3600X and an Asus X470-Pro motherboard. No issues at all with Slackware-current and the stock kernel.
Compatibility with the X570 chipset remains to be seen, but i doubt there would be any problems other than the possibility of some onboard devices requiring a newer kernel than 4.19.

The reported Linux with Ryzen 3xxx problems appear to be isolated to only distros using SystemD. However, there is already a microcode update in the works to get the RdRand instruction working the way SystemD expects. SystemD has already been patched to work around this as well.

Out of curiosity, are they still afflicted with the lock on idle problem? (Having that here. Turned on "typical current idle," although I thought that was provided by rcu_nocbs=0-whatever? So far so good.)

That is something I haven't encountered on any Ryzen systems I have worked on so far. Perhaps I have been extremely lucky with 3 different motherboards (B350M-A, X370M Pro4, X470-Pro) and 4 different CPUs (1200, 2400G, 1700x, 3600x).
I do know others have had some ongoing issues with sleep states and some combinations of motherboards and pcie cards.

Just to add to the information here: I have been running Slackware -current with a Ryzen Threadripper 2950X for a couple of weeks now with absolutely zero issues of any sort. No extra parameters added to Lilo, no workarounds, it has just worked out of the box.

Mind you this CPU has been around for a while now, the interest will doubtless be with the Ryzen 3 release...

Glad to hear about your success. I am dying to build a new system from the 3 series, just waiting to get my confidence up.
Thanks
John