is813cs@pyr.gatech.EDU (Cris Simpson) (08/11/89)
This may be a religous question and has probably been asked before:
I have heard that "smart" Ethernet cards actually reduce throughput
on fast PCs. This seems to be because the 80188 on the card working
full time is slower than a 80386/20 or 25 working part time. Is this
true? If so, at what processor speed does this make a difference?
In particular, does anyone have experience with the 3com 3c503
(Etherlink II) vs. the 3c505 (Elink Plus) ?
Eternal gratitude, etc. , etc.
cris
l
in
--
|| Gee, do you think it'd help if I plugged in both ends of this cable? ||
Cris Simpson Computer Engineer VA Rehab R&D Center
GATech Atlanta,GA
is813cs@pyr.gatech.edu ...!{Almost Anywhere}!gatech!gitpyr!is813cshrich@emdeng.Dayton.NCR.COM (George.H.Harry.Rich) (08/13/89)
In article <8960@pyr.gatech.EDU> is813cs@pyr.gatech.edu (Cris Simpson) writes: > > This may be a religous question and has probably been asked before: > >I have heard that "smart" Ethernet cards actually reduce throughput >on fast PCs. This seems to be because the 80188 on the card working >full time is slower than a 80386/20 or 25 working part time. Is this >true? If so, at what processor speed does this make a difference? > There are two potential gains from using an intelligent adapter: (1) Processing time -- by overlapping i/o processing with processing in the main CPU. (2) Memory -- by locating i/o programming in the card rather than in main memory. Assuming that you are using a DOS PC, there is relatively little opportunity for overlap of main processor and i/o processing. In addition, a major chunk of the i/o processing is managing the transfer between the card and main memory. This, of course, must be accomplished regardless of the IQ of the adapter. There is little, if any, gain to be had from the processing, response points of view from an intelligent LAN adapter. (The speed of the LAN actually forces a "dumb" LAN adapter to be considerably more intelligent than a "dumb" common carrier adapter). I have experience with processing being moved off a slow intelligent LAN adapter to improve overall system performance. However, memory under DOS can be extremely critical. If this is the case in your system(s) an intelligent LAN adapter may give you some relief. However, some LAN software is capable of taking advantage of extended and/or expanded memory, in which case the cost trade off is between an intelligent adapter, and a dumb adapter plus memory increment. If you are using OS/2 or Unix on you PC there is more opportunity for overlap. You may have to do some direct testing to find out whether the LAN processor or main processor availability is more critical in your application. My suggestion, is that if your are using 3Com software as well as hardware that you get their performance representations for each configuration. Luck, Harry Rich Disclaimer: The views expressed here are not necessarily those of my employer.
epsilon@wet.UUCP (Eric P. Scott) (08/14/89)
In article <8960@pyr.gatech.EDU> is813cs@pyr.gatech.edu (Cris Simpson) writes: >In particular, does anyone have experience with the 3com 3c503 >(Etherlink II) vs. the 3c505 (Elink Plus) ? I can't claim \extensive/ experience with these two cards, but can offer some practical advice: If you want performance, go with the 503. If you want software support, go with the 503. If you want to save money, go with the 503. If you want to run a braindead real-mode environment (e.g. MSDOS) and need to scrounge every byte you can out of the lowest 640K, go with the 505. -=EPS=-
bither@apollo.HP.COM (David Bither) (08/26/89)
>I have heard that "smart" Ethernet cards actually reduce throughput >on fast PCs. This seems to be because the 80188 on the card working >full time is slower than a 80386/20 or 25 working part time. Is this >true? If so, at what processor speed does this make a difference? Like all religious questions, it's a complex issue with no simple answers. IF the smart card processor is significantly slower than the CPU, and IF the task is single-threaded (i.e. the CPU has nothing better to do than wait for the transaction to complete) THEN a dumb card can provide better performance. In general, smart cards have a higher throughput that is only realizable in parallel or pipelined environments where some concurrency is advantageous. In general, dumb cards have a lower latency which will translate into better performance in a single-threaded environment. My experience with 3Com's Etherlink Plus card has taught me that unless you can use the intelligence to do some useful protocol processing, the board will be slower than a dumb board. Dave Bither