| T.R | Title | User | Personal
Name | Date | Lines |
|---|
| 856.1 | | NETRIX::thomas | The Code Warrior | Fri Feb 12 1993 02:14 | 1 |
| The DEFZA does not do DMA on transmit. (ie. DMA is only done for receives)
|
| 856.2 | try the new FDDI Turbochannel adapter | QUIVER::WASHABAUGH | Born to be Mild | Fri Feb 12 1993 15:37 | 5 |
| Can you try the new FDDI Turbochannel adapter? It has both transmit and receive
DMA, and generally has a more efficient architecture. It has performed quite
well in the lab.
doug
|
| 856.3 | | POBOX::DCARROLL | | Fri Feb 12 1993 20:29 | 15 |
|
Doug,
First..thanks for you response....but I/we still don't understand why
there would be no DMA on the XMIT side of a hi-speed FDDI controller.
My customer is a highly technical, widely respected national lab and I
can't go back to them with merely "buy the new adapter to solve the
problem". They are threatening to broadcast this wide and loud on
Internet unless they get a straightforward answer.
Second..I have to beg ingnorance of any new FDDI T-channel controller.
Is this announced? If not can you indicate where I can get preliminary
details.
I greatly appreciate any details you can provide. Thanks !!
Denis
|
| 856.4 | reasons why there are not transmit dma | QUIVER::WASHABAUGH | Born to be Mild | Fri Feb 12 1993 22:18 | 16 |
| There are two reasons why the first FDDI adapter (the turbochannel 700) did not
have transmit DMA. The first reason is that it was quicker time to market to not
do transmit DMA (TTM was of primary concern, not performance). The second reason
is that the west coast folks argued that transmit DMA would not buy the customer
anything. [I don't think they counted CPU cycles as being important to a
customer.
The receive DMA engine has several limitations as well. First, the firmware gets
involved in each and every packet, and second, a minimum of 512 bytes is DMA'd,
even for 1 byte of data. This can increase latency for small packets
unnecessarily.
I'm not exactly sure of the status of the DEFTA (the new turbochannel option).
Contact Sharon ONeill for details.
doug
|
| 856.5 | Are there any DEFZA -> DEFTA upgrade plans ? | ANTIK::WESTERBERG | Stefan Westerberg DS Stockholm | Sun Feb 14 1993 16:05 | 3 |
| Are there any DEFZA -> DEFTA upgrade plans ?
Stefan
|
| 856.6 | Contact PM regarding adapter upgrade programs | QUIVER::STEFANI | I've got a pocket full of Kryptonite | Sun Feb 14 1993 19:32 | 8 |
| Stefan,
You should probably send mail to Sharon (DELNI::ONEILL) Oneill regarding
any DEFZA to DEFTA upgrades. She is the product manager for all of the
FDDI Adapters (DEMFA, DEFEA, DEFZA, DEFTA, et al).
- Larry Stefani
DEFEA Project Engineering
|
| 856.7 | Why is this called a "problem"? | KONING::KONING | Paul Koning, A-13683 | Tue Feb 16 1993 14:05 | 5 |
| Something about this "highly respected lab" bothers me. The adapter works
exactly as described. Why are they upset? Did someone tell them it has
DMA both ways? It doesn't, never did, never will, never was designed to.
paul
|
| 856.8 | | STAR::PARRIS | VMS is VMS is OpenVMS now | Wed Feb 17 1993 12:23 | 6 |
| The DEFZA was out a long time (a year?) before the VS4000-90 came out, and used
on DECstations under Ultrix, so its design tradeoffs undoubtedly had the fast
MIPS CPU speed factored in. The early TURBOchannel SCSI disk controllers don't
do DMA in either direction, by the way.
I think a good trade-in offer is probably the best way to go.
|
| 856.9 | don't insult the speed of VS4000/90 | MUDDY::WATERS | | Wed Feb 17 1993 15:14 | 21 |
| >The DEFZA was out a long time (a year?) before the VS4000-90 came out, and used
>on DECstations under Ultrix, so its design tradeoffs undoubtedly had the fast
>MIPS CPU speed factored in.
Correct me if I'm wrong, but some NVAX models are *faster* than
DS 5000/200 and perhaps DS 5000/240. Certainly the difference in CPU
speed is minor.
My theory: Unix and VMS users tend to have different ways of using
machines, and different monitoring tools. Perhaps the high CPU expense
of driving DEFZA is less visible on Ultrix than on VMS. And for
historical hardware reasons, VMS users are more likely to closely
watch the disappointing progress of their jobs, and to diagnose
performance killers in the system. 8^)
I've heard a Digital vice president champion programmed I/O even on
slow, low-cost VAXes. "The CPU chip makes a great DMA engine. Our
performance study shows that dedicated DMA hardware doesn't help much."
This argument fails to recognize that some users have multiple tasks
running at once.
--gw
|
| 856.10 | .7 "bothers me" | POBOX::DCARROLL | | Wed Feb 17 1993 15:39 | 13 |
| Not that the author of .7 deserves a reply re: the design of the DEFZA
but I do wonder if he was on the GM gas tank design team?? I find the
"never designed to " quote most amusing...I'm sure the engineers at the
"highly respected" lab would also....maybe you'd like to relay that
message?
Because of the fact that early SCSI disks didn't do DMA as pointed out
in .8, we made a point to find out if this device did DMA...guess we
just "forgot" to ask if it was bi-directional.
Also , in reply to .8 what Decstation was faster than the 33 spec
VS4000 when the DEFZA was first introduced?
|
| 856.11 | | KONING::KONING | Paul Koning, A-13683 | Wed Feb 17 1993 20:51 | 7 |
| Well, you originally talked about this as if it were a bug, which of course
it isn't. It may have been a bad design decision (though the opinions of
several highly respected senior people are, at best, mixed on that).
But your only recourse is to tell the customer "yes, you're right, it doesn't
do DMA".
paul
|
| 856.12 | Fix is easy - go with DEFTA | LEVERS::WEAVER | | Thu Feb 18 1993 17:38 | 15 |
| When the DEFZA was introduced it was one of the first FDDI adapters on
the market. It was less than half the form factor of the closest
competitor and less than half the price. I don't think we should get
into a pissing contest about a decision made over 3 years ago to only
do DMA in one direction in order to complete the product design in
under 6 months. Thats not going to solve the customers problem. The
FEFTA hardware has been completed almost a year ago and it has been
working with a driver for at least 6 months. It will be released with
an OSF driver in March and a VMS driver in something like May.
It is the highest performance FDDI adapter available for sale by anyone
today. NOTE - it may not be the lowest latency but it is the best for
moving the most Mbits/sec. Hopefully you can work something out where
they can trade the antique DEFZA's for DEFTA's.
I will try and post the product announcement for the DEFTA as the next
reply - if I can't I will mail it to this notes originator.
|