Xmodem thruput?

[gar]

080220-1009 EST USA

I have posted this question on cnczone and so far no one has provided feedback. So I will try here.

I am current looking at Xmodem communication to and from HAAS using Hyperterminal.

Settings at HAAS 115.2 kbaud, 8 data bits, parity none, 1 stop bit, and obviously Xmodem which means no hardware, or Xon-Xoff, or DC codes.

Same settings at IBM PC in HyperTerminal and FIFOs disabled.

Sending from HAAS to PC the rate is about 2700 characters per second with no retries. The theoretical maximum thruput should be 115200/(1+8+1) = 11,520 characters per second. This has to be reduced by the overhead of header, checksum, and ACK --- 128 / (3+128+1+1) = 0.962 . So theoretical max is 11,520 * 0.962 = 11,082. Thus, thruput efficiency is 2700 / 11,082 = 24.4 %.

I do not remember the value but the other night I ran a test from HyperTerminal to HAAS. The efficiency was much better, but I believe below 50%.

My test file for transmission was about 170,000 bytes.

Is all the problem at HAAS, or partial, or not at all? How much of the problem is HyperTerminal?

Can anyone else confirm my results, and/or with a different communication program?

In non-Xmodem mode thruput is quite close to theoretical maximum using Cimco Edit.


Then I added additional information.

Continued experiments:

The transfer rate from HyperTerminal to HAAS is about 4000 bytes/second or 4000/11082 = 36% efficiency. Much better than in the other direction, but not good.

With a different sending program my thruput was 6870 or an efficiency of 62%.

I believe the next step is to monitor with a scope and see how much delay exists from the end of a packet until HAAS sends an ACK byte to the sender. This should provide us with information on the maximum possible thruput with our 2000 HAAS receiving.


Maybe one of our HAAS factory people will respond.

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[Haas_Apps]

Originally Posted by gar 080220-1009 EST USA I have posted this question on cnczone and so far no one has provided feedback. So I will try here. I am current looking at Xmodem communication to and from HAAS using Hyperterminal. Settings at HAAS 115.2 kbaud, 8 data bits, parity none, 1 stop bit, and obviously Xmodem which means no hardware, or Xon-Xoff, or DC codes. Same settings at IBM PC in HyperTerminal and FIFOs disabled. Sending from HAAS to PC the rate is about 2700 characters per second with no retries. The theoretical maximum thruput should be 115200/(1+8+1) = 11,520 characters per second. This has to be reduced by the overhead of header, checksum, and ACK --- 128 / (3+128+1+1) = 0.962 . So theoretical max is 11,520 * 0.962 = 11,082. Thus, thruput efficiency is 2700 / 11,082 = 24.4 %. I do not remember the value but the other night I ran a test from HyperTerminal to HAAS. The efficiency was much better, but I believe below 50%. My test file for transmission was about 170,000 bytes. Is all the problem at HAAS, or partial, or not at all? How much of the problem is HyperTerminal? Can anyone else confirm my results, and/or with a different communication program? In non-Xmodem mode thruput is quite close to theoretical maximum using Cimco Edit. Then I added additional information. Continued experiments: The transfer rate from HyperTerminal to HAAS is about 4000 bytes/second or 4000/11082 = 36% efficiency. Much better than in the other direction, but not good. With a different sending program my thruput was 6870 or an efficiency of 62%. I believe the next step is to monitor with a scope and see how much delay exists from the end of a packet until HAAS sends an ACK byte to the sender. This should provide us with information on the maximum possible thruput with our 2000 HAAS receiving. Maybe one of our HAAS factory people will respond. .

Gar,
There seems to be a lot of information missing about your tests. How long is your cable, are you using a switch box somewhere in the connection, are there any potential sources of electrical interference? I don't think you will ever reach 100% efficiency.

Many years back I had set up some serial communications (Xon/Xoff 2400bps) to BTR's on some older machines with tape readers. Everything worked great. One day I had heard on the local news that we might experience some interference with satellite communications from some solar activity. I really did not think much of it until I had to attempt to send programs to machines multiple times. Your communications could be getting interference from sources beyond your control.

[gar]

080220-1129 EST USA

Haas_Apps:

Cable length has nothing to do with the observered results.

I indicated that in non-xmodem mode that thruput is near theoretical maximum.

What I failed to mention in the post was that there were no indicated retries. Thus, no packet errors.

The un-named program used to send to HAAS at 6800 bytes/second is a DOS program run on a DOS machine.

There is latency somewhere. Is any of it at the HAAS end?

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[gar]

080220-1708 EST USA

An experiment from this afternoon:

Monitoring data flow with a scope. Sending program was HyperTerminal.

All of the thruput latency problem is at the sending end (computer) when sending to HAAS.

The theoretical time to send one packet is:
(1/11.52)(3+128+1) = 0.0868 * 132 = 11.45 MS. On the scope I measured about 5.8 x 2 = 11.6 MS which correlates very well.

The delay from the end of the packet to the ACK from HAAS varied from 0.4 to 1.0 MS. Thus, for the longest delay to ACK the total time is 12.45 MS, and for 128 bytes that is a maximum possible effective thruput of (1000/12.45)*128 = 80.23 * 128 = 10,281 bytes per second. Something is grossly wrong at the sending end for there to be about 32 - 12.45 = 19.55 MS of wasted time.

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[gar]

080221-2253 EST USA

I downloaded a version of TeraTerm, 3.1.3.0, and I did not get it to communicate with HAAS in Xmodem. I only attempted to send to HAAS. It does not look like a good program for me to try to explain to someone via phone on how to use the program.

I did some more controlled experiments with our DOS program sending to HAAS. Packet to packet time was 12.2 to 13.5 MS by scope measurement. If we assume an average of 13 MS, then the thruput is 1000/13 = 76.9 packets per second, or 128*76.9 = 9846 bytes per second. This is 11.45/13 = 88% of theoretical maximum thruput at 115.2 kbaud and 8N1 for setup.

Next I will run a timed test on a large file.

Our DOS program links with HAAS very quickly. A couple seconds. And you can start communication from either end. HAAS puts out a NAK every second until link occurs. HyperTerminal takes a very long time to link. Seems like minutes. TeraTerm never linked.

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