<Several S-100 manufacturers who were still at it in the mid-80's had
<regulated +5V on the S-100 backplane. Those who wanted to use their
<older S-100 cards in such a machine just jumpered across the 7805's and
<viola!
More commonplace was the use of constant Voltage transformers or simple
preregulation so the +8 really was +8 and not +12 when lightly loaded.
Allison
Eric wrote:
>Tim wrote:
>> According to what I read from the web page, there's a PC-clone switching
>> power supply followed by a "boost" switching circuit to get back to
>> +8 and +/- 16. That's not completely unreasonable, but it sounds a
>> little bit fishy to me in the sketchiness of the details.
>It sounds a *lot* fishy.
Well, I wasn't going to say so, but indeed it does sound something
like vaporware.
> For the required current, it would be more
>expensive to try to use a standard PC supply with custom step-up converters
>on the outputs than to simply:
>
>1) Hack a stanard switcher
>
>2) Build a custom switcher
>
>3) Have one of the switcher manufacturers build a slightly customized model
But a standard PC-clone switching supply is so common that they're
almost free, so it may be the place to start. Again, I think we may
be talking about vaporware, so perhaps a technical discussion about the
way something should/shouldn't be done is silly when it'll never be done
anyway.
>I've been thinking about replacing the power supply in my IMSAI because
>the transformer has shorted turns and is delaminating. I've been looking
>at stuff from Vicor. Not cheap, but high quality and reliable.
Certainly, there are many expensive high quality and reliable solutions
to getting 8V at tens of amps and +/- 16V at a few amps. But I can't
think of any really cheap solutions that are high quality and
reliable.
--
Tim Shoppa Email: shoppa(a)trailing-edge.com
Trailing Edge Technology WWW: http://www.trailing-edge.com/
7328 Bradley Blvd Voice: 301-767-5917
Bethesda, MD, USA 20817 Fax: 301-767-5927
>I'm not sure that "jumpering across" the 7805 will be healthy for the 7805.
>Of course, if the input doesn't drop below the output during shutdown this
>may not be a concern.
Maybe I was unclear on what I meant by "jumpering across": you put a
wire between pin 1 and pin 3 of the regulator. With such a jumper,
it's impossible for the input to drop below output at the regulator.
Of course, you've got to remember to remove the jumper before putting
the resulting card back into a system with unregulated power busses!
Like I said, regulated S-100 power busses were done by several manufacturers
in the early and mid-80's with great success. It's a non-issue.
--
Tim Shoppa Email: shoppa(a)trailing-edge.com
Trailing Edge Technology WWW: http://www.trailing-edge.com/
7328 Bradley Blvd Voice: 301-767-5917
Bethesda, MD, USA 20817 Fax: 301-767-5927
It must be you, Pete -- no duplicates in my mailbox . . .
Glen
0/0
In a message dated 8/17/99 3:23:21 PM EST, peter(a)joules.enterprise-plc.com
writes:
<< Are others on th list receiving duplicte posts or is it just me. If it is
general then is ot a problem with the list server or has everyone's mail
client gone up the spout at the same time ;-)
Regards
Pete >>
What you say is true, but the cases you bring up are not the same.
The teensy regulator providing power for a processor is designed with pretty
solid knowledge of the behavior of the load. The + 8 Volt supply in an
S-100 box is a completely different thing, with loads which vary widely from
one application to another, and, for that matter from one day to another.
If you reversed the bias on the little regulator on a processor, the current
stored in the processor would be negligible. If you have a memory circuit
on an S-100 card, you probably have forty small capacitors and half a dozen
larger ones (e.g. 33 uF) which would be sourcing current to the 7805
regulator(s) while the input now sources current to the disk drives or
whatever other low-impedance loads run from that supply.
I'm with you about the use of switchers which save on energy and reduce
waste from dissipation. However, the proposed "booster" hasn't been thought
through yet. They're not very cost-effective, nor do they offer much power
per buck.
The problem with linear supplies is not their intolerance of high voltage
inputs, but rather, my intolerance of their high temperature when operating
at a high input/output ratio, as the regulator dissipates it all as heat.
That's not likely to happen here, however.
Dick
-----Original Message-----
From: jpero(a)cgocable.net <jpero(a)cgocable.net>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Tuesday, August 17, 1999 4:50 PM
Subject: Re: imsai 2
>> Date: Tue, 17 Aug 1999 16:35:15 -0600
>> Reply-to: classiccmp(a)u.washington.edu
>> From: "Richard Erlacher" <edick(a)idcomm.com>
>> To: "Discussion re-collecting of classic computers"
<classiccmp(a)u.washington.edu>
>> Subject: Re: imsai 2
>> X-To: <classiccmp(a)u.washington.edu>
>
>> I'm not sure that "jumpering across" the 7805 will be healthy for the
7805.
>> Of course, if the input doesn't drop below the output during shutdown
this
>> may not be a concern. However, if there's a significant off-board load
on
>> the input switching supply, and significant capacitance (bypass, for
>> example) on the board, it's likely to cause problems.
>>
>> Dick
>
>Hi,
>
>Actually that is not harmful thing. In fact, nearly all peecees of
>any brands and generic of any quality short out the 3.45V regulator
>via input and output to get 5V by either a jumper or a low
>resistance/high current capable FET in (automatic detection type like
>GX4, SP3 and such by Asus for 486). I'm sure that is same story for
>the split or single voltage supply modes for Pentium class boards.
>
>One thing about double PSUing from one to another voltages is bit too
>much to me from reliablity and cost viewpoints. Feeding 5V and
>12V direct to bus is assumed that designer upsize the conductors
>enough to keep voltage drops low.
>
>THERE is decent PSUs that can be had in any voltages in multi outputs
>from one box and still be switcher. I'm all for switchers for
>efficieny and less heat output of quality built.
>
>Most linear regulators are happy on input voltages up to 30V BTW.
>
>Wizard
I suspect that there's quite a little work to be done on the IMSAI product
before the first fully functional one will be shipped. I've got standard
switchers which would do the job, i.e. their outputs can be adjusted to
provide the needed current, e.g. 8V at 25 Amps, +/-12 16 @ 5 & 3 amps, or
maybe less. These weigh less than the transformer supplies on the half
dozen or so S-100 frames I've got, and, when size and weight are viewed from
the standpoint of handling, storage, and shipping costs, they may even cost
less. However, unless one anticipates volumes in excess of 1% of annual PC
sales, the cost will not be comparable with PC supplies.
Dick
-----Original Message-----
From: Eric Smith <eric(a)brouhaha.com>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Tuesday, August 17, 1999 4:45 PM
Subject: Re: imsai 2
>Tim wrote:
>> According to what I read from the web page, there's a PC-clone switching
>> power supply followed by a "boost" switching circuit to get back to
>> +8 and +/- 16. That's not completely unreasonable, but it sounds a
>> little bit fishy to me in the sketchiness of the details.
>
>It sounds a *lot* fishy. For the required current, it would be more
>expensive to try to use a standard PC supply with custom step-up converters
>on the outputs than to simply:
>
>1) Hack a stanard switcher
>
>2) Build a custom switcher
>
>3) Have one of the switcher manufacturers build a slightly customized
model
>
>I've been thinking about replacing the power supply in my IMSAI because
>the transformer has shorted turns and is delaminating. I've been looking
>at stuff from Vicor. Not cheap, but high quality and reliable.
>
Well . . . freight cost alone might be justification for using switchers.
Nevertheless, I don't see a use for the regulated supplies in connection
with a bus which by definition uses on-board regulation. If the supply
actually provides the specified voltages, that's a different situation. The
typical S-100 box, IIRC, used lots of amperes, even for just one memory
board, and generated lots of heat. The average, even BIG, PC supply is not
beefy enough to support a typical S-100 box as I remember them. 8 of the 8K
SRAM boards with 2102's . . . well, you figure it out! There were other
ways to go, of course, but back in the day of the 22-slot backplane, that's
what justified the backplane's size. Power for the entire remainder of the
system was not that much.
Dick
-----Original Message-----
From: Jeffrey l Kaneko <jeff.kaneko(a)juno.com>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Tuesday, August 17, 1999 4:33 PM
Subject: Re: imsai 2
>
>
>On Tue, 17 Aug 1999 16:11:10 -0600 "Richard Erlacher" <edick(a)idcomm.com>
>writes:
>
><Stuff SNIPped>
>
>> What puzzles me is why the IMSAI folks decided to use a switching
>> power supply when the box and everything else already supported the
>needs
>> of the S-100 with the previously available and now quite inexpensive
>> unregulated supplies of yesteryear.
>
>Well, for a given wattage, switchers are smaller, lighter, and more
>economical to produce. I imagine if they resorted to the old iron-core
>transformers of yore, they would have had a difficult time finding
>a supplier for them.
>
>When they did, the part would probly cost as much as the rest of the
>materials put together. Makes perfect sense to me.
>
>
>Jeff
>
>
>___________________________________________________________________
>Get the Internet just the way you want it.
>Free software, free e-mail, and free Internet access for a month!
>Try Juno Web: http://dl.www.juno.com/dynoget/tagj.
Though it's not consistent with my own bent, the "new" IMSAI offers a "safe"
place in which to play with those extremely costly boards some folks have
picked up from the eBay auctions.
What puzzles me is why the IMSAI folks decided to use a switching power
supply when the box and everything else already supported the needs of the
S-100 with the previously available and now quite inexpensive unregulated
supplies of yesteryear. One of the main benefits of the S-100 was that it
had on-board regulation, so that if you didn't need a given supply, you
didn't have to bring it on board and regulate it, dissipating power as you
went. If the new box is capable of running the original boards, it must
provide the raw 8 and +/- 16-volt supplies. Where's the benefit in having a
switching regulator sitting in the back of the box? I suppose it creates a
market for a power distribution module to put +5 and +/- 12 on each board
which needs it rather than using the on-board regulators, but that opens
another can of worms. What's the "right" way to distribute it without
tampering with a historically correct board?
Dick
-----Original Message-----
From: allisonp(a)world.std.com <allisonp(a)world.std.com>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Tuesday, August 17, 1999 1:44 PM
Subject: Re: imsai 2
>> >
>> >It wasn't F11 though it could be done. It was a LSI-1 and later the
T11.
>> >Also Alpha micro used the same chipset as LSI-11 do do the AM100.
>>
>> Neat...I sure wouldn't mind getting ahold of one of those. They're
pretty
>> rare, I'd guess, no?
>
>Likely rare as the company was not a big one and PDP-11 on s100 would be
>rather unDEC in the software support. At best rt11 might have been doable
>if all the device drivers were rewritten. I'd bet those that were sold
>(the bulk of them) are in embedded systems.
>
>The alpha micros were pretty popular though not cheap and they may be more
>common.
>
>Allison
>
>
Are others on th list receiving duplicte posts or is it just me. If it is general then is ot a problem with the list server or has everyone's mail client gone up the spout at the same time ;-)
Regards
Pete
On Aug 17, 0:37, Derek Peschel wrote:
> To keep this on topic... The RT-11 (or RSX-11?) installation program
> determines whether your machine is using 50Hz or 60Hz power. If 50Hz, it
> tells you to make a cup of tea (because the installation takes a long
time).
> If 60Hz, it tells you to make a cup of coffee.
It's RSX-11.
OB nitpick: On Aug 17, 0:35, Mike Ford wrote:
> Tetly
> Taylors of Harrowgate (non cheap UK import)
Actually, Tetley, and Taylors of Harrogate.
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
