15 Jun
2002
15 Jun
'02
4:09 p.m.
Bob Shannon -
Could you expand on your comments about non-s-100? According to the
website, it has a 10 slot S-100 MB, and "The IMSAI SERIES TWO utilizes
the powerhouse Zilog Z8S180 microprocessor and provides a complete
system on an IEEE-696 compatible S-100 board"
I am somewhat interested in the machine, but not if there is NO chance
of using some of my other S-100 boards in it.
Bob Stek
Saver of Lost Sols
15 Jun
15 Jun
5:02 p.m.
My initial reading (more or less my last) of the spec for the new Imsai is
that the power supply is a regulated switcher that provides the "standard"
voltages (though they're no longer standard) of +/- 5 and +/- 12 volts.
Normal S-100 hardware had on-board regulation, hence expected to see +8 and
+/- 16 on the bus.
That alone would do it, I think. The fact that it's IEEE696-standard will
ensure that some of your boards won't work, simply because the standard allows
some bus pins to be used for either signal, ground, or a supply. If it uses
it as -7 and you think you've got a clock there ... well ...
Dick
----- Original Message -----
From: "Bob Stek" <r.stek(a)snet.net>
To: <cctalk(a)classiccmp.org>
Sent: Saturday, June 15, 2002 3:09 PM
Subject: Re: IMSAI News?
Bob Shannon -
Could you expand on your comments about non-s-100? According to the
website, it has a 10 slot S-100 MB, and "The IMSAI SERIES TWO utilizes
the powerhouse Zilog Z8S180 microprocessor and provides a complete
system on an IEEE-696 compatible S-100 board"
I am somewhat interested in the machine, but not if there is NO chance
of using some of my other S-100 boards in it.
Bob Stek
Saver of Lost Sols
9:56 p.m.
My initial reading (more or less my last) of the spec
for the new Imsai is
that the power supply is a regulated switcher that provides the "standard"
voltages (though they're no longer standard) of +/- 5 and +/- 12 volts.
Normal S-100 hardware had on-board regulation, hence expected to see +8 and
+/- 16 on the bus.
This isn't awfully new in the S-100/IEEE696 world; in the 80's Compupro
sold a number of IEEE696 systems that distributed regulated +5V instead of
unregulated ~8V, courtesy of a switching power supply.
To put a "regular" S-100 board in all you had to do was jumper around
its on-board voltage regulators, no big deal.
Tim.
10:47 p.m.
That's true, but CompuPro hardware of different families, though they all
claimed compatibility with S-100, didn't even work in different CompuPro
environments, and that wasn't just after the adoption of the standard. In
fact, CompuPro/Bill Godbout was instrumental in watering down the standard to
such extent that it essentially guaranteed the demise of the S-100, since it
allowed for so much incompatibility that not even they could manage it.
The power supply and its management was the least of your worries with their
hardware. However, if your board required +/- 15, which was pretty easily
regulated from the +/- 16, which was seldom limited to 16, you'd be in real
trouble with the 12 volt bipolar supply.
Further, I'd say, though it's not "new" nowadays, it was practiced only
a
short time in the life of the S-100. I think the deviation from the standard
practices, not necessarily the "standard," was what led to its death,
actually.
Dick
----- Original Message -----
From: "Tim Shoppa" <classiccmp(a)trailing-edge.com>
To: <cctalk(a)classiccmp.org>
Sent: Saturday, June 15, 2002 8:56 PM
Subject: Re: IMSAI News?
> My initial reading (more or less my last) of the
spec for the new Imsai is
> that the power supply is a regulated switcher that provides the
"standard"
> voltages (though they're no longer standard) of +/- 5 and +/- 12 volts.
> Normal S-100 hardware had on-board regulation, hence expected to see +8
and
+/- 16 on the
bus.
This isn't awfully new in the S-100/IEEE696 world; in the 80's Compupro
sold a number of IEEE696 systems that distributed regulated +5V instead of
unregulated ~8V, courtesy of a switching power supply.
To put a "regular" S-100 board in all you had to do was jumper around
its on-board voltage regulators, no big deal.
Tim.
16 Jun
16 Jun
6:09 a.m.
The power supply and its management was the least of
your worries with their
hardware. However, if your board required +/- 15, which was pretty easily
regulated from the +/- 16, which was seldom limited to 16, you'd be in real
trouble with the 12 volt bipolar supply.
Further, I'd say, though it's not "new" nowadays, it was practiced only
a
short time in the life of the S-100. I think the deviation from the standard
practices, not necessarily the "standard," was what led to its death,
actually.
If I was going to do it today, I'd stick with the ~8V unregulated bus and
use a small buck switching regulator on each card. You get all the efficiency
of a switcher, and compatibility with older stuff.
With "Simple Switchers" from NatSemi (or equivalent from Motorola/Onsemi/
TI etc.) it's very easy to do. What's really good is that many of the
electronics distributors which let their inductor selection whither away
over the years now have excellent selections of inductors - some of which
they keep in stock! :-)
Tim.
9:18 a.m.
On Sun, 16 Jun 2002, Tim Shoppa wrote:
If I was going to do it today, I'd stick with the
~8V unregulated bus and
use a small buck switching regulator on each card. You get all the efficiency
of a switcher, and compatibility with older stuff.
Why not stick a SPDT switch on each slot on the bus to switch between the
regulated vs. unregulated supply for each slot? Of course you'd then have
to somehow supply the unregulated voltages.
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
* Old computing resources for business and academia at www.VintageTech.com *
10:53 a.m.
Sellam Ismail wrote:
Why not stick a SPDT switch on each slot on the bus to
switch between the
regulated vs. unregulated supply for each slot? Of course you'd then have
to somehow supply the unregulated voltages.
Go one better. Make the switch a small pushbutton and have some
mechanical protusion on the modern cards push the switch to select the
regulated supply. Old card would not have the protrusion and would
receive unregulated volts.
-- hbp
17 Jun
17 Jun
12:23 a.m.
If you poke around in the DigiKey catalog a little bit I'll be you can find
the TO-220 switchers that somebody or other sells. There are also some that
sit on TO-3 footprints, though neither type is as small as the genuine
package. Another problem is that the small switchers still only put out about
a half to maybe one ampere, and I've got a few S-100 boards that have two or
three three three-amp regulators on them. Several others have a TO-220 for
each of four banks of SRAMs.
Dick
----- Original Message -----
From: "Tim Shoppa" <classiccmp(a)trailing-edge.com>
To: <cctalk(a)classiccmp.org>
Sent: Sunday, June 16, 2002 5:09 AM
Subject: Re: IMSAI News?
efficiency
> The power supply and its management was the least
of your worries with
their
> hardware. However, if your board required +/-
15, which was pretty easily
> regulated from the +/- 16, which was seldom limited to 16, you'd be in
real
> trouble with the 12 volt bipolar supply.
>
> Further, I'd say, though it's not "new" nowadays, it was practiced
only a
> short time in the life of the S-100. I think the deviation from the
standard
practices, not
necessarily the "standard," was what led to its death,
actually.
If I was going to do it today, I'd stick with the ~8V unregulated bus and
use a small buck switching regulator on each card. You get all the of a switcher, and compatibility with older stuff.
With "Simple Switchers" from NatSemi (or equivalent from Motorola/Onsemi/
TI etc.) it's very easy to do. What's really good is that many of the
electronics distributors which let their inductor selection whither away
over the years now have excellent selections of inductors - some of which
they keep in stock! :-)
Tim.
8:14 p.m.
If you poke around in the DigiKey catalog a little bit
I'll be you can find
the TO-220 switchers that somebody or other sells.
Yeah, Powertrends (now owned by TI) makes them. I prefer the NatSemi
simple switchers over the all-in-one one Powertrend units, which are
are largish chunks of epoxy and metal on the end of three TO-220 legs.
Another problem is that the small switchers still only
put out about
a half to maybe one ampere, and I've got a few S-100 boards that have two or
three three three-amp regulators on them.
The 150kHz and 250kHz NatSemi units are 5-legged TO-220's and do 3A and
5A quite comfortably. You need room for the inductor, of course, but
small ones are very readily available.
Tim.
18 Jun
18 Jun
8:38 a.m.
There are some "ready-to-use" products in this line from NS. That gives you a
PCB about 1.5" x 0.5" x 0.6" high with unregulated power in and regulated
power out, with a common connection at ground. I think they call this an
evaluation unit, but they sell 'em.
There's still no ideal solution. The smallish NS products are still too
large, as are the PowerTrends products. I guess it depends on how much of a
kludge you're willing to put on your boards. I personally believe the S-100
is S-100 and it should be run from an unregulated supply using the on-board
regulators for which the original design made provision. If you want
something else, you can use something more modern, but don't try to fool
yourself in to believing it's S-100 when you're done.
I rather believe that Todd Fischer's goal in using a switcher was based on the
low cost of the "PC" switcher, which is grossly overrated, power-wise, and its
relatively low shipping weight. My belief is that if you want to run classic
hardware, you should run it as shipped. If you don't need to run the classic
hardware, then run a simulator. It's less costly and runs lots faster.
Dick
----- Original Message -----
From: "Tim Shoppa" <classiccmp(a)trailing-edge.com>
To: <cctalk(a)classiccmp.org>
Sent: Monday, June 17, 2002 7:14 PM
Subject: Re: IMSAI News?
or
> If you poke around in the DigiKey catalog a
little bit I'll be you can
find
the TO-220
switchers that somebody or other sells.
Yeah, Powertrends (now owned by TI) makes them. I prefer the NatSemi
simple switchers over the all-in-one one Powertrend units, which are
are largish chunks of epoxy and metal on the end of three TO-220 legs.
> Another problem is that the small switchers still only put out about
> a half to maybe one ampere, and I've got a few S-100 boards that have two
three three
three-amp regulators on them.
The 150kHz and 250kHz NatSemi units are 5-legged TO-220's and do 3A and
5A quite comfortably. You need room for the inductor, of course, but
small ones are very readily available.
Tim.
8236
days inactive
8239
days old
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