Graphics cards in 2018 - looking for suggestions

Hello chaps,

I've just undergone a trial of tears attempting to upgrade the milling PC to something a little more modern over the last couple of weeks, but I'm coming to realise that I may be stuck at a dead end without having to fork out some money for a different machine.

Currently I'm running Ubuntu 10.04 from the LiveCD install on a Asus P5Q Deluxe, 4G RAM, AMD Core2 Q9600 and Radeon HD3450. Software stepping via the parallel port (RTAI kernel).

Have tried Debian Wheezy, Linux Mint 18,3 32bit and Linux Mint 18.1 64bit.

The problem I'm experiencing is that latency is too unstable with any install of LCNC on a newer OS than Ubuntu 10.04, unless I knobble the Radeon HD3450 graphics card. Spikes over 300k when moving/resizing windows or opening new ones. If I disable the Radeon (radeon.modeset = 0 in Grub) I can get rock-solid sub-10k latencies under all situations, so it's obviously the ancient Radeon that's the common issue amongst all variants of the OS. But I obviously lose my dual monitors and decent resolutions if I go back to the generic drivers.

Onboard video is not an option as the Asus P5Q lacks a built-in graphics chipset.

So the question I have is - is there a modern PCI graphics card with dual outputs that anyone can recommend that won't break the bank and isn't made of unobtainium that is known to work with more recent distributions of Linux?

Cheers.

I've run one of these:
www.ebay.com.au/itm/Lenovo-ATI-FRU-89Y61...p2057872.m2749.l2649
With an Asus M2N68-AM Plus with 1GB Ram & AMD athlon 64X2 and got sub 10k Latencies with Wheezy

and one of these:
www.ebay.com.au/itm/Lenovo-03T7092-AMD-R...p2057872.m2749.l2649
With a Asus AN8-SLI Deluxe with 4GB Ram and an Athlon 64 3500+ and got sub 10k Latencies with Wheezy

My experience has been the AMD Athlons and Radeon cards give better latencies than an Intel solution and a Nvidia card....I've tried both Core2 core & i5 combos.

If you are running LinuxCNC on a CPU less than 10 years old, you typically don't need a graphics card at all

Thanks for the input, Ozzyrob. I'll keep an eye on cards such as those.

The Radeon HD3450 I have in the PC at the moment works perfectly with Ubuntu10.04 and with Windows 10 which this PC has a dual boot with. It just doesn't want to play completely cleanly with any other Linux distro I've tried thus far.

If you are running LinuxCNC on a CPU less than 10 years old, you typically don't need a graphics card at all

andypugh wrote:

I have always (every single time) used onboard video and have never found it to be a problem.

That's been my experience also when configuring other off-the-shelf PCs to run with LCNC. However, as I mentioned in the first post, the P5Q motherboard does not have any onboard graphics capability, so unfortunately I am stuck with either fitting a graphics card of some variety or replacing the entire mobo (which isn't exactly what I had in mind for the computer).

tommylight wrote:

If that is an AGP slot card, try finding an Matrox G400 dual head, that will work nicely.
If you have PCI-E, go into bios and disable PCI-E power saving and everything related to it.
That should do it. If it does not, you have a card that is soon to fail.

Thanks Tommylight. Yes, have tried disabling all the usual power-saving features in bios, but still no joy. Only thing I've found that works so far is disabling the Radeon drivers (looks ugly and graphics performance becomes very jerky) or sticking with Ubuntu 10.04 (works fine, but does mean I can't run some of the software packages I'd like to use on an out-of-date OS).

I've just plonked down the cash for one of those HD5450 cards. For 26 bucks I reckon it's worth a try.

Some success.

While waiting for the new card to turn up I went scouring the interweb for some instruction on the Radeon driver. Turns out there a bunch of options that may be further specified to tune the driver beyond the default options. Maybe this is obvious to seasoned Linux users, but for mere mortals such as myself coming from a Windows background, this wasn't entirely clear.

FWIW, the following has got my latency back to a stable <16k figure in Mint 18.1. Not blisteringly fast, but on par with the previously-working Ubuntu 10.04 install, and completely usable for software stepping:

1. Create a new blank file in /etc/X11. Call it xorg.conf
2. Enter the following information:

   Section "Device"
   	Identifier	"Radeon"
   	Driver		"radeon"
   	Option		"Accel"		"off"
   EndSection

3. Save and reboot

By turning off hardware acceleration on the HD3450 (ie, the line that reads Option "Accel" "off") I seem to have corrected the erratic latency spikes while retaining good graphical performance and my dual monitor setup. It will be interesting to see if the HD5450 needs this tweak as well when it arrives.

I'd be curious to know if other users have experienced similar issues. Does this point towards an additional tweak that can be performed on a system that otherwise appears unusable beyond all the regular latency fixes in BIOS?