Conference 7.286::fddi

Suprised noone has taken a crack at this one... I can speak for PDQ based 
adapters only (Not sure about DEFZA is being upgraded, but its kind of a dog
anyway, so there are software limitations that prevent full bandwidth).

PDQ based adapters can do a total of 160mbits, in the right conditions.  The
xmt or rcv side can do up to 100 mbits, and the other side can suck up the
remaining 60 mbits.  Of course that's just hardware.  The bus is the next
potential bottleck.  EISA/PCI/FUTUREBUS have no problem, plenty of bandwidth
to spare.  I doubt that ISA (if we do one) or QBUS busses can support full
FDDI so, in these cases the bottleneck is the bus.

The last remaining bottleneck is CPU.  Depending on the OS and hardware
platform, some people are seeing over 100 bits (using ALPHA machines).  As
a plug for our adapter, I think that our adapter generally uses less CPU
cycles than competitors, so we should do well in cases in which the CPU
is the bottleneck.

doug

    I heard that the DEFTA can do, "100 Mbits/second for transmit and 
    about 98 Mbits for receive and about 100 Mbps total for full duplex". 
    This is consistent with results I've seen with the bricks demo.
    
    You listed EISA/PCI/FUTUREBUS as busses that have plenty of bandwith,
    but not turbo channel.  Is the turbo channel too slow?  Or is it just
    the DEFTA?
    
    From experiments with the bricks demo with a GIGAswitch, a dual
    processor Cobra with a DEFAA running VMS and UCX, and a few Flamingos
    with DEFTAs running OSF/1, I think you could really see full duplex
    there but I never had all the right components together at the right
    time to actually prove it.  
    
    You would need a working GIGAswitch, a dual processor cobra, a DEFAA,
    and either two Flamginos with DEFTAs or another dual processor Cobra
    with another DEFAA. 

I mistakenly omitted DEFTA as an adapter that can do the 160 mbits full duplex.
Turbo is a great bus, fast and easy to interface to.

I thought there had been an experiment similiar to what you described, and 
bricks did about 117mbits, but I'm not sure.  Ask Venkat Kalkunte.

doug

re .1, �PDQ based adapters�, 
 can you explain PDQ, please? Do we have others?

greg.

PDQ (actually, is does not stand for Pretty Damn Quick in this instance) is a 
ASIC (a *large* ASIC) which does most of the work (DMA, buffering, ...) 
involved in being a FDDI station.  The DEFTA, DEFEA, DEFAA, DEFIA, ... all use
it (basicly and FDDI adapter after the DEMFA uses the PDQ chip).

    re: .3
    
    Yes, actually, I've seen the DEFTA do full duplex, but not very much
    over 100Mbps total - over, but not much.  
    
    So, the DEFTA and the turbo channel can do 160, so the limit I heard
    (in .2) must be the flamingo or the operating system??

doug

    Hi All......
    
    Does anyone know when DEC will be releasing Microcode for the DEMFA
    which will support FULL DUPLEX on the GIGGA switch..   At present I
    believe the latest version is V1.4...
    
    Can anyone supply me with a DTN for the Engineering focus for the DEMFA
    
    Thanks in advance
    
    Tony Rees
    DTN :-  7833 3047
    MCSC Basingstoke
    HANTS
    

Version 2.0 is available which allows the DEMFA to work in FULL DUPLEX. You can
find the spd in VTX SPD

DEC FDDIcontroller 400 Software Microcode V2.0     SPD 32.31.04

    Thanks for your help.....  will retrieve document ASAP
    
    Tony