Hi Jason - maybe this is the reason I seem to have trouble running dCore X86_64 debian_stretch on my UEFI-ONLY boxes ...
I ran the iso through Rufus and took a look at the logs. Aside from no gpt in the iso, maybe Syslinux 4.02 is a tad too old? Check the iso analysis section..
Rufus x86 v3.5.1497
Windows version: Windows 10 64-bit (Build 17763)
Syslinux versions: 4.07/2013-07-25, 6.03/2014-10-06
Grub versions: 0.4.6a, 2.02
System locale ID: 0x0409 (en-US)
Will use default UI locale 0x0409
SetLGP: Successfully set NoDriveTypeAutorun policy to 0x0000009E
Localization set to 'en-US'
Notice: The ISO download feature has been deactivated because the remote download script can not be accessed.
Found USB 2.0 device 'SanDisk Cruzer Blade USB Device' (0781:5567)
Using autorun.inf label for drive D: 'Porteus'
Found card reader device 'Toshiba 032G34'
1 device found
Disk type: Removable, Disk size: 16 GB, Sector size: 512 bytes
Cylinders: 1946, Tracks per cylinder: 255, Sectors per track: 63
Partition type: GPT, NB Partitions: 1
Disk GUID: {B79BE815-D66C-483C-8F3B-78F4E22C23B8}
Max parts: 128, Start Offset: 17408, Usable = 16008575488 bytes
Partition 1:
Type: {EBD0A0A2-B9E5-4433-87C0-68B6B72699C7}
Name: 'Microsoft Basic Data'
ID: {0C60D641-C329-43DD-8D4F-23F88EF23C5A}
Size: 14.9 GB (16007544320 bytes)
Start Sector: 2048, Attributes: 0x0000000000000000
Scanning image...
ISO analysis:
Image is an ISO9660 image
Will use '/boot/isolinux/isolinux.cfg' for Syslinux
Detected Syslinux version: 4.02/debian-20101014 (from '/boot/isolinux/isolinux.bin')
Disk image analysis:
Image has an unknown Master Boot Record
Image is a bootable disk image
ISO label: 'dCore-stretch64'
Size: 189.4 MB (Projected)
Note: File on disk is larger than reported ISO size by 244 KB...
Uses: Syslinux/Isolinux v4.02
Using image: dCorePlus-stretch64.iso (190 MB)
Format operation started
Requesting disk access...
Will use 'D:' as volume mountpoint
Deleting partitions...
Deleting ALL partitions from disk '\\?\PhysicalDrive1':
● Partition 1 (offset: 1048576, size: 14.9 GB)
Opened \\.\PhysicalDrive1 for exclusive write access
Analyzing existing boot records...
Drive has a Zeroed Master Boot Record
Clearing MBR/PBR/GPT structures...
Erasing 128 sectors
Deleting partitions...
Partitioning (MBR)...
Closing existing volume...
Waiting for logical drive to reappear...
Formatting (FAT32)...
Using cluster size: 8192 bytes
Quick format was selected
Creating file system...
Format completed.
Writing master boot record...
Drive has a Zeroed Master Boot Record
Partition is already FAT32 LBA...
Set bootable USB partition as 0x80
Using Syslinux MBR
Found volume GUID \\?\Volume{e1f98de3-a1f2-11e9-8594-d8c4971025d1}\
Installing Syslinux 4.02...
Opened \\?\Volume{e1f98de3-a1f2-11e9-8594-d8c4971025d1} for shared write access
Successfully wrote 'ldlinux.sys'
Successfully wrote Syslinux boot record
Successfully remounted \\?\Volume{e1f98de3-a1f2-11e9-8594-d8c4971025d1}\ on D:
Copying ISO files...
Extracting files...
Image is an ISO9660 image
This image will be extracted using Joliet extensions (if present)
Extracting: D:\boot\dCorePlusstretch64.gz (185.5 MB)
Extracting: D:\boot\isolinux\boot.cat (2 KB)
Extracting: D:\boot\isolinux\boot.msg (219 bytes)
Extracting: D:\boot\isolinux\f2 (870 bytes)
Extracting: D:\boot\isolinux\f3 (1003 bytes)
Extracting: D:\boot\isolinux\f4 (865 bytes)
Extracting: D:\boot\isolinux\isolinux.bin (24 KB)
Extracting: D:\boot\isolinux\isolinux.cfg (472 bytes)
Extracting: D:\boot\vmlinuzstretch64 (3.9 MB)
Created: D:\syslinux.cfg
Finalizing, please wait...
Created: D:autorun.inf
Created: D:autorun.ico
Found USB 2.0 device 'SanDisk Cruzer Blade USB Device' (0781:5567)
Using autorun.inf label for drive D: 'dCore-stretch64'
Found card reader device 'Toshiba 032G34'
1 device found
Disk type: Removable, Disk size: 16 GB, Sector size: 512 bytes
Cylinders: 1946, Tracks per cylinder: 255, Sectors per track: 63
Partition type: MBR, NB Partitions: 1
Disk ID: 0x017102FA
Drive has a Syslinux Master Boot Record
Partition 1:
Type: FAT32 LBA (0x0c)
Size: 14.9 GB (16007561216 bytes)
Start Sector: 2048, Boot: Yes
I'm far from a boot expert - and appreciate what you (and the tc guys do as well!) Just wondering if this is part of the problem I'm facing that may not be showing up on older gear that guys are running...