Viewing Logs on Startup volume that freezes I have a MacBook Pro (Computer A) which freezes / restarts during startup.
To investigate the problem, I purchased a brand new internal disk and did a basic installation (10.13 - the latest this model supports) on a working MacBook Pro (Computer B). This clean install boots on at least 4 Macs I have at my disposal.
But, on Computer A, it will startup, the progress bar will advance to about 60% and then it will restart and do the same thing. Or it will freeze the second time.
When I booted in Verbose mode, the last lines I got were:
DSMOS has arrived
Unsupported CPU
Unsupported CPU
Unsupported PCH
AppleHDAEngineOutput::performFormatChange (&lt;ptr&gt;, &lt;ptr&gt;, 0)
en2: promiscuous mode enable succeeded
IOConsoleUsers: time(0) 0-&gt;0, lll 0, llk1,
IOConsoleUsers: gIOScreenLockState 3, hs 0, bs 0, now 0, sm 0x0

at which point it hung.
I booted Computer B in verbose mode and was able to look at the logs and follow those error messages, but there are many additional lines there that aren't displayed on the screen during verbose mode startup.
If I boot Computer A in Target Disk mode, I can mount its disk on Computer B, so I don't believe the SATA cable is the problem.
Ultimately, I'd like to determine what the root of the problem is, but an interim step is to compare the log files from the disks in Computers A and B.
Is it possible to look at the log file from Computer A while accessing its disk as an external disk on Computer B?
(If you have an idea why it might be restarting/hanging, I'd welcome help on that, too.)
I'm having the exact same problem with a client's 12,1 iMac.  I think it's hopeless for the iMac, but you might be able to put your MBP into relatively working condition if it has two graphics cards (you didn't mention what model you have).  If it does, then only one of them is busted (the AMD Radeon HD 6750M has come unsoldered), so you have to prevent the machine from trying to use it.  If you have an Intel HD Graphics 3000 card in there as well, you might be able to work off it.  Here's the GitHub guide:
https://gist.github.com/cdleon/d1eff7246a25193304284ecec40445b0
Here's the annoying (but insightful) YouTube video that led me to this discovery:
https://youtu.be/iLft4N54zvU
Check out both, give it a try, and please let me know how it goes.