64 bit Linux поддерживает 64 bit network counters?

Да.

# uname -isrm
Linux 2.6.16-archck1 x86_64 AuthenticAMD


# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:14:85:39:F3:99
          inet addr:10.0.0.1  Bcast:10.0.0.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:151048 errors:0 dropped:0 overruns:0 frame:0
          TX packets:82284 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:215079231 (205.1 Mb)  TX bytes:6870113 (6.5 Mb)
          Interrupt:20 Base address:0x2000

eth1      Link encap:Ethernet  HWaddr 00:04:79:67:1B:0E
          inet addr:192.168.0.1  Bcast:192.168.0.255  Mask:255.255.255.0
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
          Interrupt:16 Base address:0xc000

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:27422790 errors:0 dropped:0 overruns:0 frame:0
          TX packets:27422790 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:446033915882 (425371.0 Mb)  TX bytes:446033915882 (425371.0 Mb)

>http://www.ussg.iu.edu/hypermail/linux/kernel/0402.2/0960.html

По поводу 32 бит.
 cli
> addl %eax, (%ebx) # Sum low word
> adcl %edx, 0x04(%ebx) # Sum CY and high
 sti

Вот так должно работать :)

Отлично, меня это радует.