Subject of some Mac Apps/OS X installers downloaded in the past not working due to expired apple security certificate came up again. This was noted in the Feb 9th news (Aspyr warning about Apple security cert expiring Feb 13th affecting some of their Mac App store games, and Apple dev news on renewed cert.) Also the Feb 17th news had a reader tip on setting date back to use OS X installers with an expired cert. (Has happened before.)
And in case any OS X Snow Leopard users missed it, late last month Apple posted a Mac App Store Update for OS X 10.6.8 that includes a renewed intermediate signing certificate required to continue using the Mac App store and run previously purchased apps that use receipt validation.
Different clock rates reported on Dual D500 (2013 Mac Pro) (apple mac pro forum) Shows one D500 running at 725MHz and the other 150MHz per LuxMark 3 (v3.1?) hardware devices report. (A reply from another OS X 10.11.3 user with D300's showed same clock rates for both GPUs per LuxMark.) IIRC, one GPU is used for display(s), the other for compute. I wonder if the D500 owner checked after running a benchmark in case the 2nd GPU throttled down when idle. (I've never owned a 2013 Mac Pro but curious if the GPUs have variable clock rates, which I saw years ago even with much older AMD and Nvidia graphics cards. The clock rate would ramp up when needed (running graphics or games, etc.) and lower when idle. In some old tests of Nvidia and ATI cards I saw 300/400/648MHz modes for a GTX-285 and 240MHz idle on a Radeon 4890's 850MHz GPU.)
Mac Pro 2009 with 4K (UHD) TV for monitor? (apple forums)
("4K" TVs are UHD res (UltraHD, 3840x2160 or 2160P) vs true 4K 4096x2160.
UHD retains 1080P HD's aspect ratio by doubling Horizontal & Vertical Resolution.)
Doesn't say what graphics card he has, but says it has a Mini DisplayPort (called it Thunderbolt by mistake). Replies include suggestions for MDP to HDMI adapters and comments on HDMI 2.0 adapters. Before buying an expensive HDMI 2.0 adapter check for owner feedback, it hasn't been good for some. Of course replacing the graphics card is another option but that can be expensive and not always PnP.
(FYI: Here's apple's doc on Mini DisplayPort to HDMI adapters, which notes 2009 Mac Pros don't support audio output via MDP (or HDMI). That was another benefit of the 2010-2012 Mac Pro 5,1 EFI/bootrom which some have flashed into the 4,1 Mac Pro. IIRC there was also a driver mod workaround.)
Not sure from the question but if he's just looking for basic function (vs driving it from the Mac at 3840x2160/60P), try a standard MDP to HDMI (1.4) adapter and the TV will scale the input to its native res automatically. (For example if OS X desktop set to 1920x1080 resolution (60Hz) the UHD TV will fill the screen by upscaling that to its native 3840x2160, 60Hz.) Some of the replies to his post make it seem like he can't get over 30Hz unless he uses a HDMI 2.0 adapter - this is not true if he is OK with just running a lower resolution setting in OS X like 1920x1080. The TV will automatically upscale it. 1080P upscaled on a 4K/UHD TV (60Hz) looks fine to my eyes, but I don't need to work in 4K in OS X. HDMI 1.4 can do UHD at 24/30P but that's a very low refresh for monitor use. (24P typically used for Movies/blu-rays. Some HDMI 1.4 blu-ray players have an upscaling option for UHD 24P.) (Although it doesn't apply to his Mac Pro/TV, some Macs & Displays can do 60Hz 4K/UHD via Multi-Stream Transport (MST). See Use 4K displays & Ultra HD TVs with your Mac.)
For sharpest image/text, you want to make sure no overscan is used so set the TV (Samsung in his case) to "Screen Fit". (LG calls that mode "Just Scan".) In my older Samsung that option is in the Picture>Screen Adjustment>Screen Size menu. And here's a doc on OS X settings. (My Mini->AVR->TV setup looks fine as-is (w/o tweaks to RGB), but an old tip for direct connected Macs (where you can't easily change output mode to RGB vs YCbCr) was to set the HDMI input port used on the TV to "PC" mode/rename the input "DVI PC". On the 2012 Samsung TV I have, you use the Source button, "Tools" option to rename an input. Tools option only worked for inputs that were active.) If you output RGB from the Mac and see washed out image (check gamma setting first) or incorrect black levels on the TV, you may have to adjust the TV's HDMI black level setting if it doesn't detect it correctly. (TVs usually have options for RGB limited (video) 16-235 or full (PC) 0-255 range modes. RGB range setting names can vary by TV brand - i.e. low/high, limited/full, and some may have an auto setting.) It may be different in his UHD Samsung TV, but my 2012 Samsung calls 16-235 range 'low' and 0-255 'normal', and "HDMI Black Level" option is in the "Picture Options" menu. (If sent YCbCr, my Samsung does not allow changing HDMI black level (grayed out), although the LG OLED does. I saw it used to correct severe black crush with X-Files season 8 on blu-ray which was apparently encoded using 0-255 in the initial release.)
(I had previously mentioned temporarily using my 2012 Mac Mini HDMI port (running 1920x1080 in OS X) with a UHD LG TV and unlike some owners, I had no video dropouts every 7 seconds when connected via an A/V Receiver to the TV. At the bottom are notes/info on EDID mods.)