From:	CRDGW2::CRDGW2::MRGATE::"SMTP::CRVAX.SRI.COM::RELAY-INFO-VAX" 27-OCT-1989 02:51
To:	MRGATE::"ARISIA::EVERHART"
Subj:	Re: RE: DEPCA Alternatives

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Date: 27 Oct 89 03:29:40 GMT
From: unmvax!pprg.unm.edu!topgun.dspo.gov!whitfill@ucbvax.Berkeley.EDU  (Jim Whitfill)
Organization: Los Alamos National Laboratory
Subject: Re: RE: DEPCA Alternatives
Message-Id: <2055@topgun.dspo.gov>
References: <8910261834.AA09459@ucbvax.Berkeley.EDU>
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in article <8910261834.AA09459@ucbvax.Berkeley.EDU>, COMBSTM@ALF.APPSTATE.EDU ("Terry M. Combs") says:
> 
>>       Would someone be kind enough to point me in the direction of a cheaper
>>alternative to DEC's DEPC Card. Last I looked they go for 600-1200 dollars
> 
>>Is there a way we can use PCSA on IBM PC / XT clones attached to a VAX via
>>a cheaper card than DEPCA???
>>
> There are alternatives under PCSA 2.2.  The following cards were pointed to at
> a seminar given by Digital about 6 months ago in our area:
> 3Com501
> 3Com503
> 3Com523
> Micom5010
> LANCE
> DEPCA
> 
> As pointed out someone bought 50 at a nice price, but not everyone can spring
> for 50, even though they may need 50 over a couple of years.  There are 3C501
> cards which run around $220-275, qty 1.  However, not all cards are equal.  I
> understand the 3C501 card is single buffered, old, and sloooow, but if you
> aren't concerned so much about speed as about cost, that's the card for you.
> Also if you are looking for an alternative, be sure there is a driver under
> PCSA which supports the card (You probably are aware of this).
> 
> 
> We have tested the 3C501 card and the Western Digital Ethercard + using the
> NCSA freeware.  They work.
> 
> - Terry
>   Bitnet: COMBSTM@APPSTATE

Terry is correct, the 3com501 (and the Micom5010) are very slow. We have
done some tests with both cards and compared them to Depca cards. We have
found that the Depca can transfer many small files (~200 files between
2k and 11k bytes) between 5 and 10 times faster than the other 2 cards. We put
an Ethernet monitor on the LAN to see what was happening and found that the
server (a VAX 6320) was having to resend between 40% and 50% of the data
buffers because the PC couldn't turn the single buffered cards around fast
enough to catch the first occurance of the data buffer. The single buffered
cards cannot have a receive ready to go when they transmit, so the PC must
reset the card for a receive once it has transmitted. If the server is a
fast one, this causes a lot of misses. DEC told me that we would get better
overall performance if our server were a MicroVAX II if we use the slow
cards because they won't miss so much data. Each time a data buffer is missed,
there is a 5-10 second timeout on the server before it retransmits.

The 3Com503 card is a multibuffered card like the Depca and we plan on 
testing it also.

BTW, I don't think the DEPCA's are as expensive as stated in the original
of this chain. I seem to recall that they are running about $399, including
a right to copy the Client software......


-----------------------------------------------------------------------------
Jim A. Whitfill			        Los Alamos National Laboratory (LANL)
whitfill@meediv.dspo.gov      	              Group MEE-5, MS J572
whitfill@meediv.lanl.gov	      	      Los Alamos, NM 87545
                                	         (505) 667-9282