There's good reason to cast about for a general purpose bus on the order of
the middle-period S-100. The PC's of tomorrow will have no expansion slots
at all and will rely on USB, SCSI, and the various parallel port protocols
to do "practical" I/O. That will be very limiting. I don't know what folks
will do in cases where they have measurements, telememtry, process control
tasks, or whatever to do. The PC has never been particularly well suited
for such tasks, since there were such meager offerings in the way of general
purpose I/O.
The common microcontroller setups are pretty costly, often much more so than
a Pentium based PC with thousands of times the computing power.
By the time it was standardized, the S-100 was pretty well settled.
Unfortunately, the amateur computer enthusiasts presented a bigger market
than the measurement and control people, of whom I was one, and so it was
pretty important to be able to build one's own interface circuits. For
that, the S-100 was not as friendly as it could have been. Because of the
legacy of 8080 signals and signal timing, even though the system usually had
a sensible processor which could have worked very well, there tended to be
glitches as caused by the fact that it took maybe three signals and a
decoder to sense a local I/O cycle, yet the bus provided six or seven, and
various board makers didn't use the same ones, nor did they use them in the
same way. That's a mistake that should be avoided in the future. By
contrast, the Multibus-I had signals somewhat similar to those on the ISA,
and they were simple, easy to understand, and so on. Of course Intel led
the charge on MB-I.
See comments below, plz
Dick
-----Original Message-----
From: Allison J Parent <allisonp(a)world.std.com>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Saturday, July 03, 1999 10:14 PM
Subject: Re: OT: A call to arms (sort of)
><Why do you assume that ISA -> Intel processor? It may be something
><totally different, something that doesn't have efficient block transfer
><instructions.
>
>Like a z280?
>
You must really love that chip, Allison, but yes, even that, if you wish.
It's YOUR computer, after all, so it should be the way YOU like it.
>
><I see a _lot_ wrong with the ISA signal definitions. For one thing the
><IRQs are edge triggered, active high, when any sane designer would make
><them level triggered active low (had IBM done this it would have cost
><them an extra couple of TTL chips on the PC motherboard. It would also
><have allowed the sharing of interrupts). For another thing there's no
><proper bus request/grant (multiple masters are almost essential IMHO).
>
>So the interrupts are upsidedown and stoopid, it's useful as is none the
>less. The yabut is for small systems it's fine.
>
><As I understand it, the aim is to make a PC (meaning something that runs
><a useful open OS like linux or *BSD) and which has 'modern' features like
><a good video card. Not to make the equivalent on an S100 system
>
>Consider possibility number 3, something that is hybrid, having the
features
>of S-100 like system but modern I/O and a different bus.
>
I personally would favor the 96-pin connector (per DIN 41612) as used in
VME, but only one, for a basic card and make it on the nominally 4.5 x 6"
form factor of the single slot EUROCARDS (e.g. VME). That connector is more
reliable than card-edge connectors and it's used enough that it's relatively
cheap. It's compatible with a 0.100" matrix so a card and a backplane could
( if you were REALLY desperate and impoverished ) be made by hand on a good
wire-wrap card. Those are a few pretty compelling reasons. Of course
unless you actually adopted the VME standard, you'd still be on your own and
unable to buy a serial card or such.
>
><> known, and one doesn't need a video board right off the top. The
WD1003-
><> board is well uderstood and the EIDE interface emulates that pretty well
><
><Sure. Now where do you propose getting schematics for this I/O card, and
><where are you going to get a data sheet on the ASIC that almost certainly
><appears on it. This is supposed to be _open_ hardware. This implies full
><schematics, not undocumented PCBs.
>
This is where I'd recommend caution if you use q-bus. The schematics must
not only be available and complete, but they must be correct as well. PALs
must be fully characterized, something I've never seen in a DEC product,
and, in fact, I'd say you have MUCH less "open" information about q-bus than
about ISA. The problem with ISA is that the information was usually "out
there" well in advance and then, when the product was shipped, wasn't
available any more, because there were too many competitors and the doc cost
an extra few pennies.
>
In reality, building an I/O mux onto a current generation PC parallel port
makes as much sense as anything. With EPP you can get up to 2MB of transfer
bandwidth, in bursts, of course. That's not bad . . . AND you have a "real"
computer with "real" tools that's very fast and "real" cheap.
>
>Treat the card as a functional black box. Herc, CGA and VGA video is well
>enough known and the addresses are not secret. It's not a requirement to
>knwo the tiny design details of the 8042 keyboard controller to get it to
>give keycodes. Most of the floppies are the base 765 circuits pushed into
>a chip, same for serial and IDE is not a secret. Based on what I've seen
>of some of those cards the less I know the better!
>
>Allison
>
<I know that several people on this list have used minix. Can anyone tell
<me if the book is worth buying with respect to understanding the OS?
YES! I have the book and it's quite informative anput OS design in general
and why Minix is what it is. It's a pretty neat small kernel unix like OS.
There is also Minix-VMD on the net that's to Kees as well as a version that
will run on a dos box.
Allison
<In this bridge circuit with a 12 volt supply:
<
<+12 -------
< A B
< .LOAD..
< C D
<return-----
The last design I did in the analog realm was a 500w per channel
that could be bridged for 1000W. (for studios and theatures) I am
acutely aware of the topology of bridge amps and power measurement.
<(A, B, C, D) are switches, either A, D or B, C on,
<The 4 Ohm load sees a maximum current of 3 Amps in either direction.
or 24V PP with 6a. Keep in mind it takes 6A to move the coil through the
full range it will travel with this 24VPP signal. It will move forward
3A(12v) worth from the resting position and it will move rearward the
same distance with the reverse polarity but it will take 24v6a to make
it transverse the same path in a continious cyclic way.
<That is 1.5 Amps for each of two 8 Ohm speakers in parallel.
<The maximum (peak) power is 36 watts, 4x that of a non-bridged amplifier.
<"peak to peak power" is just a marketroid term. Actually I don't even use
<the term "RMS power", as IMHO, "RMS" applies to voltage or current, not pow
Oh boy... RMS WATTS are measured using real RMS Amps and real RMS Volts
across a real (non inductive load). A real 500w amplifier heats a 4ohm
resistive load the same as pluging it into a ~45V RMS AC source. As long
as you know what is meant all the terms are valid. One of the problems
with small amplifers is the power supply is tepid to weak and often they
can actually supply full load power for one or two cycles until the PS
voltages fade due to lack of iron and copper in the core. I have a 35W
(continous RMS) stereo amplifer I built and due to the transformer (not
enough core) but plenty of Capacitor it can in short bursts deliver 55W
(10 cycle pulses of 400Hz @<.1%). There are far more dynamics than discussed
though some of the numbers are really meaningless.
Most of those wall cubes are very limited and 30-40W is about the limit,
often less. There are a few switchmode designs for wall cubes at will pack
70-80w output into something 4x1x2 but those don't go cheap.
Allison
<You may be a victim of the infamous "RD53 spindown problem". Does the
<drive spin up and then stop and/or recycle, or fail to reach full speed?
The other cause is the positioner gets stuck in the shutdown position and
the drive not finding the servo will also shutdown and cycle.
The fix has been detailed elsewhere but opening the HDA and fixing it is
a viable option.
Allison
Please see comments embedded below.
Dick
-----Original Message-----
From: Tony Duell <ard(a)p850ug1.demon.co.uk>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Saturday, July 03, 1999 6:55 PM
Subject: Re: OT: A call to arms (sort of)
>>
>> With the ISA, it depends on the TYPE of DMA you use. If you use one of
the
>> channels on the motherboard, there sould be no problem. It's only a bit
>> shaky if you try to run it from the bus itself. That's because of
>
>Sure. But the Unibus/VME/etc way where the _peripheral card_ generates
>the addresses for DMA (rather than there being a central DMA controller)
>is a lot cleaner IMHO
>
Yes, it is, and with the PC motherboard gone, there's nothing to prevent one
>from using that method.
>
>> motherboard features. Since there's to be no motherboard, i.e. only a
>> passive ISA backplane, that shouldn't be a limitation. It's not
necessary,
>
>Eh? If you're going to have an ISA bus (meaning a bus where you can stick
>standard PC expansion cards) you _have_ to have the DMA controller. Even
>an FDC card really needs it. You can't start suddenly redefining odd
>signals and call the result ISA.
>
Leaving off the motherboard doesn't change the BUS to something else. There
have been systems with multiple processors on passive backplanes for the ISA
for years. You don't have to change one signal. Of course, if you leave
off the motherboard, i.e. the circuitry that makes it a PC, then you don't
have to use the otherwise useless 4x-color-burst crystal oscillator either,
and you don't have to generated that inane 18... Hz interrupt and can use
something sensible instead, and you don't have to generate refresh addresses
with one DMA channel, and you don't have to use DMA for the floppy which
will work fine without it, and . . .
>
>Of course you can have a similar bus with mostly the same signals, but
>with bus request/grant signals and an arbitration scheme like
>Unibus/VME/etc. But most ISA cards would _not_ work on thse bus.
>
>
>> in general, to have DMA, first because the processors used on PC
>> motherboards have block transfer operations which operate at the bus
>> bandwidth.
>
>Why do you assume that ISA -> Intel processor? It may be something
>totally different, something that doesn't have efficient block transfer
>instructions.
>
Now you're confusing me . . . you just got through saying that the PC has to
be there, Intel and all, or it's not an ISA bus. Perhaps you spoke (sic)
too soon? I made no such assertion! There are lots of processors which
have block transfer instructions which operate at the bus bandwidth. Even
the Z80 did that.
>>
>> The only things which would be inherited from the adoption of ISA as an
open
>> bus would be the connector and the signal definitions. I see nothing
wrong
>> with those. One could even punt the 14.318 MHz (4x color-burst)
oscillator
>
>I see a _lot_ wrong with the ISA signal definitions. For one thing the
>IRQs are edge triggered, active high, when any sane designer would make
>them level triggered active low (had IBM done this it would have cost
>them an extra couple of TTL chips on the PC motherboard. It would also
>have allowed the sharing of interrupts). For another thing there's no
>proper bus request/grant (multiple masters are almost essential IMHO).
>
You're certainly right about that! All that would have been needed is that
they swallow their pride and use a sensible interrupt handler instead of
their silly 8259. In fact, they should have left all their LSI's off the
MB. The way their counters work, or don't, and the fact they're slow, and
they're ripple counters so you have to read half of them twice . . . don't
get me started . . .
Of course if you're going to "fix" the mistakes, then maybe a few changes
are warranted, including a provision for multiple masters. I find multiple
masters on a single backplane of limited value. It's easy enough just to
have a drawer for each processor and let them talk to one another on a
high-speed LAN. Now that multi-Gb LANs are becoming more visible, no pun
intended, those'll be the next great leap. Changing the way the signals
work is not such a sin, since you still use the same bus definitions. A
little improvement on the ISA could go a long way.
>
>> in favor of a more useful one, or perhaps none at all.
>
>That clock (which, BTW is not synchronised to anything else necessarily)
>is the least of the problems.
>
well, if you use a color board, or a frame grabber which assumes NTSC
timing, it may want that to be there.
>
>>
>> The types of boards useful in development don't need a lot of
documentation
>> to be used outside the MSDOS/PC world. The base locations of the 8250's
on
>
>As I understand it, the aim is to make a PC (meaning something that runs
>a useful open OS like linux or *BSD) and which has 'modern' features like
>a good video card. Not to make the equivalent on an S100 system
>
>> I/O boards is know, the base of the printer port (twisted though it is)
is
>
>The base address of the printer port is no more twisted than that of the
>serial ports. I've read the ROM source code, and the routines that set up
>the address table are _very_ similar.
>
That was an error, i.e. i had an indefinite antecedent for the pronout "it"
in that I meant that the way the parallel port works, with some of its
signals inverted, etc, was twisted. An address is just an address.
>
>Basically, the ROM looks for printer ports at 0x3bc, 0x378, 0x278 in
>order. It assigns each one it finds to the next available 'LPT number'.
>What this means is :
>
>If you have a single parallel port at _any_ of those addresses, it will
>be LPT1.
>
>If you have 3 ports they will be LPT1 (0x3bc), LPT2 (0x378), LPT3 (0x278).
>
>If you have 2 ports, the one at the 'first' address in the table will be
>LPT1, the one at the later address will be LPT2.
>
>Serial ports are similar. It looks for 8250s at 0x3F8 amd 0x2F8. It
>assigns the first one it finds to COM1, the second one to COM2. In other
>words, if you have a single RS232 port at 0x2F8, it will be COM1.
>
>> known, and one doesn't need a video board right off the top. The
WD1003-WAH
>> board is well uderstood and the EIDE interface emulates that pretty well.
>
>Sure. Now where do you propose getting schematics for this I/O card, and
>where are you going to get a data sheet on the ASIC that almost certainly
>appears on it. This is supposed to be _open_ hardware. This implies full
>schematics, not undocumented PCBs.
>
No ASIC, just the WD 1010 which is thoroughly characterized in the old
databooks and datasheets. maybe a few other garden variety LSI's of the
early '80's. I probably have it somewhere, but there was a time when I had
the 1010 and 2010 pretty well memorized. The BMAC is an 8042 with some code
and a peek at the application notes for the 1010 will tell you what's in the
1100. Since MFM is pretty much history, or, more correctly, the drives
which used it, I'd say that's a non-issue. You don't need the schematic,
though,since the board you'll be using will be an IDE interface with onboard
FDC. Those (FDC's) are well characterized and all you need to know about
the 1003-WAH is the command set, since IDE still uses it.
The little IDE interface boards with 5 TTL's on them are easy enough to buzz
out and understand. Data on the LSI's is easy enough to get, though you
shouldn't need it if you read the data on the WD 1003 controller board.
>
>-tony
>
That's the price you pay, so to speak, for participating in a free-market
economy. The market determines what price the market will bear. If there
are more rich dummies (If that's how you prefer to think of them) than there
are Altairs or 4004's then you'll probably never own one.
Meanwhile, maybe I can get someone to slide me a few bucks for this old
stuff of mine . . .
Dick
-----Original Message-----
From: Marvin <marvin(a)rain.org>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Saturday, July 03, 1999 5:11 PM
Subject: Re: E-bay stupidity! was Re: height of folly
>
>
>Joe wrote:
>>
>> $610!!! I'll bet Intel wishes they still had some! Who was it that said
>> "A fool and his money are soon parted." ?
>
>If prior patterns follow, we will be seeing more of the 4004 microprocessor
>chips showing up now. With any luck, the first one listed pulls in a higher
>than expected price, and the following ones will slowly reach reasonable
>again.
>
>Of course it could be like the Altair where the first ones sold for about
>$600 or so, and the price went up from there, and then settled in to the
>current $2000 - $3000 or so.
Hi,
I know that several people on this list have used minix. Can anyone tell
me if the book is worth buying with respect to understanding the OS?
--Max Eskin (max82(a)surfree.com)
http://scivault.hypermart.net: Ignorance is Impotence - Knowledge is Power
Muchas Gracias to all who have offered advice and suggestions
about the teletype. The Problem, alas, is that the print carriage
has thrown one of the little nylon sliders that ride on the code
rails as it travels... I have taken the unit down to major
subassemblies but there is no sign of the slider. Damn. It is of
course the slider on codebar 5.
I narrowed this down by observing the punch, which is getting the
correct codes. Why 'return' doesn't work is a further mystery, but
it will have to wait until I can scrounge up a parts machine, or a
working one in which case this one will become the parts donor. It
is the parity machine with the forms feed unit and tractor feed
sprockets, which is nice for computer use.
Thanks again all... now to get to this 11/44 sysgen...
Cheers
John
With the ISA, it depends on the TYPE of DMA you use. If you use one of the
channels on the motherboard, there sould be no problem. It's only a bit
shaky if you try to run it from the bus itself. That's because of
motherboard features. Since there's to be no motherboard, i.e. only a
passive ISA backplane, that shouldn't be a limitation. It's not necessary,
in general, to have DMA, first because the processors used on PC
motherboards have block transfer operations which operate at the bus
bandwidth.
The only things which would be inherited from the adoption of ISA as an open
bus would be the connector and the signal definitions. I see nothing wrong
with those. One could even punt the 14.318 MHz (4x color-burst) oscillator
in favor of a more useful one, or perhaps none at all.
The types of boards useful in development don't need a lot of documentation
to be used outside the MSDOS/PC world. The base locations of the 8250's on
I/O boards is know, the base of the printer port (twisted though it is) is
known, and one doesn't need a video board right off the top. The WD1003-WAH
board is well uderstood and the EIDE interface emulates that pretty well.
That solves the mass storage problems. Serial I/O is straigtforward enough.
Where's the problem?
Dick
-----Original Message-----
From: Tony Duell <ard(a)p850ug1.demon.co.uk>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Saturday, July 03, 1999 3:24 PM
Subject: Re: OT: A call to arms (sort of)
>>
>> Well . . . what could possibly be more "open" than the ISA. It's capable
of
>> pretty much anything that the PDP-11 could dish out, AND you can get paid
>
>Well, apart from interupt sharing, multiple bus masters (the 16 bit ISA
>allows for _one_ bus master card, but it doesn't really handle it
>properly), certain DMA transfers, etc, etc, etc...
>
>> for taking the boards away from a lot of places. Almost any function you
>
>But most of these cards are _NOT_ 'open'. Try getting complete
>programmings specs for certain video cards, let alone schematics, PAL
>equations, etc.
>
>The whole idea of this is to make an open PC, _because_ existing cards
>are not fully documented.
>
>-tony
>
