[Simh] 10ms delay on ethernet communications

[Boucher, François]

Hi again!

 

Further testing shows that the problem appears between version 3.6-1 (polling of XQ is functionnal)

And version 3.7-0 (polling specification of XQ is not taken into account, and is fixed at 100 polls per second.)

 

Thanks,

 

Francois

 

________________________________

De : Boucher, François 
Envoyé : 9 janvier 2008 13:57
À : 'simh at trailing-edge.com'
Objet : 10ms delay on ethernet communications

 

Hi to all!

 

I am looking for help about the Ethernet driving of the vax simulator.  I see that there is some sort of a fixed delay of about

10ms between the time a packet is received from the network and the time it is treated in the simulator.

 

My host machine has an intel quad core 2.4GHz, 1033 MHz of FSB, 4MB cache per core, desktop, running Knoppix linux, version 5.1.

It has Ethernet cards plugged into a Cisco 2924 switch, with all port speed fixed at 100Mbps.

 

I saw in the documentation that there is a parameter for the polling frequency of the reception of packets, related to the XQ devices of the simulator.  By default, the parameter is 100 polls per second, which is consistent with the 10ms delay observed.

I did change the value of the polling parameter to 1000polls per second, but the delay stayed there on the simulator,  version 3.7-3

(The command I did was SET XQ POLL=1000)

 

So, I tried to use a previous version of simh, in this case, version 3.4, and when I adjusted the polling rate, I got a diminution of the latency time for the reception of packets.  This means that between simh 3.4 and simh 3.7-3 there is maybe some broken code about the control of the XQ polling rate.  

 

Perhaps there is something else I could do to adjust the polling rate on simh 3.7 but I don't know what.  Any suggestions would be welcomed!

 

Thanks,

 

Francois Boucher

 

 

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