MacBook Pro internal vs.. external disk issues. Please help? MacBookPro5,4 bought used on CraigsList two years ago., was working fine, but wanting to update from SL 10.6.8 to Yosemite 10.10.2... Bought a new 1TB SATA hard drive… Here are the symptoms: 1. When I tried to install Mac OS X 10.10.2 on a brand-new, formatted, partitioned INTERNAL (SATA) drive, after several hours, the install failed. Tried again, same result… Third time, the same… 2. Same drive, in EXTERNAL USB case. OS X install worked a-ok, first try — after a few hours the Mac OS X 10.10 install completed, no problems. Question #1: Should there be any difference with installing OS X on an internal vs. an external disk drive? UDMA / CRC error count creeping up... 3. Mounted the new drive internally. Booted aok. The DriveDX app reports the UDMA CRC Error Count is increasing about 5-10 errors per day. (The app suggests this could indicate a drive going bad or a bad cable.) 4. Mounted the same drive EXTERNALLY using SATA to USB external enclosure, boots AOK, and error count does not increase after more than a week in use. 5. Put same drive back inside the MBP, error count escalates again, same as #3. 6. Again, mounted as EXTERNAL, see #4, same, no new UDMA/CRC errors after another week. 7. One more thing… I have several other external drives, for TimeMachine, and alternate boot drives for 10.6.8 Snow Leopard… ::: Hard drives via USB HUB? Or, USB Direct to MBP? ::: Strange Issues ::: Each one of these hard drives in it's own external enclosure… Various brands… Same results... •• Each drive will mount AOK when plugged directly into the MPB USB ports, but •• When plugged into any USB HUB; no drive will even be seen by DiskUtility app; and will not mount. •• VIA USB HUB —— USB Flash drive works AOK; but the external USB hard drives DO NOT wok via a hub. •• Tried three different USB enclosure brands, and three different USB hubs, same result. •• NO JOY with any external USB hard drives via USB HUB; but same drives and cables work aok when connected directly to the MBP USB ports. What is going on here? I know there are other apps besides DRIVEDX … they are more expensive… I guess you get what you pay for. DriveDX provides lots of info but other apps may be better. The drive: HGST Travelstar 7K1000 HGST HTS721010A9E630 The MacBook Pro: Model Name: MacBook Pro Model Identifier: MacBookPro5,4 Processor Name: Intel Core 2 Duo Processor Speed: 2.53 GHz Number Of Processors: 1 Total Number Of Cores: 2 L2 Cache: 3 MB Memory: 8 GB Bus Speed: 1.07 GHz Boot ROM Version: MBP53.00AC.B03 SMC Version (system): 1.49f2 Question #2: I SUSPECT that the MBP motherboard may be failing, just from the above list of symptoms... The internal USB bridge is acting very strangely. Any suggestions? Further troubleshooting ideas? Take it to the shop?