[syslinux] no boot, no message

[Jorge Almeida]

I have syslinux 5.10 on a 32bit gentoo system. It boots fine. Now I
installed another linux system in other partitions of the same drive
(a 64 bit system), updated syslinux.cfg, setup the new system as
default, and the new entry appears in the menu. Problem is: it doesn't
boot. On timeout, it starts counting down again, and that's it. No
error message whatsoever. Selecting the old system by hand boots it as
usual.

Is it normal for extlinux to not produce an error message?

The extlinux partition is sda1, with ext2 fs. The motherboard is ASUS
H97-PRO. It is configured to work in CSM mode. Some maybe relevant data:

    description: Desktop Computer
    product: All Series (All)
    vendor: ASUS
    version: System Version
    serial: System Serial Number
    width: 32 bits
    capabilities: smbios-2.8 dmi-2.7 smp-1.4 smp
    configuration: administrator_password=disabled boot=normal
chassis=desktop cpus=2 family=ASUS MB frontpanel_password=disabled
keyboard_password=disabled power-on_password=disabled sku=All
uuid=E0B2C736-DAD7-DD11-AB81-40167EAD5491
  *-core
       description: Motherboard
       product: H97-PRO
       vendor: ASUSTeK COMPUTER INC.
       physical id: 0
       version: Rev X.0x
       serial: 140526027201371
       slot: To be filled by O.E.M.
     *-firmware
          description: BIOS
          vendor: American Megatrends Inc.
          physical id: 0
          version: 0333
          date: 05/08/2014
          size: 64KiB
          capacity: 15MiB
          capabilities: pci apm upgrade shadowing cdboot bootselect
socketedrom edd int13floppy1200 int13floppy720 int13floppy2880
int5printscreen int9keyboard int14serial int17printer acpi usb
biosbootspecification uefi
     *-cpu:0
          description: CPU
          product: Intel(R) Core(TM) i3-4150 CPU @ 3.50GHz
          vendor: Intel Corp.
          physical id: 46
          bus info: cpu at 0
          version: 6.12.3
          serial: 0003-06C3-0000-0000-0000-0000
          slot: SOCKET 1150
          size: 3500MHz
          capacity: 3900MHz
          width: 64 bits
          clock: 100MHz
          capabilities: x86-64 boot fpu fpu_exception wp vme de pse
tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts
acpi mmx fxsr sse sse2 ss ht tm pbe nx pdpe1gb rdtscp constant_tsc
arch_perfmon pebs bts xtopology nonstop_tsc aperfmperf eagerfpu pni
pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 fma cx16 xtpr pdcm
pcid sse4_1 sse4_2 movbe popcnt tsc_deadline_timer aes xsave avx f16c
rdrand lahf_lm abm arat epb xsaveopt pln pts dtherm tpr_shadow vnmi
flexpriority ept vpid fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms
invpcid cpufreq
          configuration: cores=2 enabledcores=2 id=0 threads=4


Thanks,

Jorge Almeida