Terrible performance of direct cable connection

Posted on 1999-12-11
Medium Priority
Last Modified: 2013-12-16
I have just setup a direct cable connection between my laptop and desktop machines, both running the same version of Win-95. Everything seems to work ok but it is terribly slow. Although I am using a serial cable I would expect it to run as fast as the DOS based INTERSVR mechanism for transfering files. Initially COM2 was set to 9600 baud but changing it to 115200 baud under the control panel didn't seem to make that much difference.

Any ideas?

Many thanks in advance.

Question by:aecooper

Accepted Solution

Zerquish earned 2000 total points
ID: 2273687
Direct cable connections are just extremely slow. The maximum speed is indeed 9600 baud, and that Windows would change it to 115200 baud is just stupid (viva Microsoft !), because it cannot be higher than 9600. If you don't believe me, check the maximum speed available for a serial mouse, since it is also connected to a COM-port. If you want higher speeds, then I recommand you buy to ethernet cards, and if you want it really fast, buy two fast ethernet cards. Those onces can get 100 Mbps instead of 10 Mbps.

Author Comment

ID: 2273925
Is there a service pack or something that will get around this limitation?
LVL 17

Expert Comment

ID: 2274557
Parallel cables transmit data simultaneously over multiple lines, making it the faster of the two connection methods. Serial cables transmit data sequentially over one pair of wires, and are slower than parallel cables.
Use a serial cable only if a parallel port is unavailable.
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Author Comment

ID: 2276831
I can get perfectly acceptable transfer rates over the serial cable by using either DOS's INTERSVR or a dedicated PPP-TCP/IP connection under Linux. Both mechanisms run at 115200. Therefore the problem lies with MS-Windows 95 - hence my previous comment about a service patch etc.

Expert Comment

ID: 2309346
You might try to set the parallel port to EPP on both machines in bios.
LVL 22

Expert Comment

by:Adam Leinss
ID: 2337322
Zerquish absolutely hit the nail right on the head with this one.  DCC is slow.  Serial transmits at 1 bit at a time, parallel 8 bits at a time.  If you need ultra fast access between two machines, use 2 networks cards and a cross over cable.  Nothing you say will convince me that serial is fast.  Nothing.

Author Comment

ID: 2356956
No one is saying its fast, its just that under a decent operating system, like Linux, I can get a PPP connection that is 6-8 times faster. In fact you can increase the baud rate. MSWIN95 sets up a couple of null modems for the direct cable connection and these modems were set to 19600 (this seemed to be the bottle neck). However increasing the baud rate just made the connection more unreliable. I'll just use INTERSVR from now on - at least that will go at 115200.

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