Date: Sun, 1 Aug 2004 23:32:18 -0400
From: "Chandra Bajpai" <cbajpai(a)comcast.net>
Subject: Xerox Alto Restoration + Emulation
>Has anyone every heard of these guys.they seem to up in Canada and are
>painstakingly restoring an Xerox Alto I since April 2003.
<snip>
That would be the Bordynuiks, Heather & John IIRC. They had a bunch of stuff
on ebay a while back, bought some pdp-11/20 memory from them. Other than
that my contact with them has been minimal.
They own pdp8.com - they had some nice stuff, including a nice pdp-15 with
drum IIRC. Think Robert Garner has that one now...
The Alto restoration is one *very* impressive bit of work, they're serious
hardware engineers - seem to recall they also (according to rumour) had
something to do with Paul Allen and his KL...
Mike
http://www.corestore.org
>From: "Marvin Johnston" <marvin(a)rain.org>
>
>
>I fired up an Altair and found it didn't behave as it should (tested
>with MITs and Polymorphic CPU cards.) Doing an "Examine" does not load
>the switch settings into the program counter. Doing an "Examine Next"
>seems to increment the program counter by 3. The preceeding was done
>with and without a memory card. I tried the "Deposit" but had no way to
>see what I was doing since the switch settings apparently weren't being
>loaded. Finally, the "Deposit Next" increments the LEDs. One other
>strangeness, when I connect the Data Display cable to the MITS card, the
>"Stop" switch ceases to function although the "Start" seems to work
>fine.
>
>I do have the schematics and will start to dig into it later this
>morning. BUT, I was hoping to short circuit some of the troubleshooting
>time if someone on the list has experienced something like this :).
>Thanks!
>
Hi Marvin
It sounds like the front panel isn't jamming the correct
instructions onto the data bus ( or something on the data
lines of the CPU is loading one of the data lines ).
The front panel works by either jamming a JMP ( 0C3h ) instruction
onto the CPU's bus or a NOP ( 00h ). This allows for both changing
address and incrementing the address. The front panel can then
override the read and write operations to the physical memory
during the increment.
The most common problem I've seen that causes similar effects
is that there are several 7406 ( or similar OC buffers ) connected
>from the front panel to the data lines of the CPU. One or more
of these devices has failed ( I suspect this is mostly do to
some overlap timing and stressing of the parts but that is
the way they are designed ). One other thing that I've seen
is that the data lines going to the CPU from the front panel
were wired upside down. This is that cable between the two.
( soemone put the cable together backwards )
Dwight
Hi Steven
I suspect that the MM78 is at least one of the
parts that I'm looking for. I regret that the
actual chips have no information on them other than
the date code and the in-house part number. There
are no generic part numbers on their labels.
Dwight
>From: steven <tosteve(a)yahoo.com>
>
>
>I have a 1984 Rockwell Data Book with lots of ICs in
>it - I will need a part number.
>
>Steve.
>
>
>--- John Honniball <coredump(a)gifford.co.uk> wrote:
>
>> Dwight K. Elvey wrote:
>> > Does anyone have any data books with the specs
>> > and signals for Rockwell's 4 bit processors that
>> > they made during the late 70's? These were in a
>> > funny flat pack called spider chips.
>>
>> I have a book by Steve Money called "Microprocessor
>> Data Book", and
>> it lists three Rockwell 4-bit chips, the MM75, MM76
>> and MM78. They
>> make up the PPS4/1 Series. Are they the ones you
>> are interested in?
>>
>> --
>> John Honniball
>> coredump(a)gifford.co.uk
>>
>>
>
>
>
>
>__________________________________
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>
>From: "John Honniball" <coredump(a)gifford.co.uk>
>
>Dwight K. Elvey wrote:
>>>From: "John Honniball" <coredump(a)gifford.co.uk>
>>>I have a book by Steve Money called "Microprocessor Data Book", and
>>>it lists three Rockwell 4-bit chips, the MM75, MM76 and MM78. They
>>>make up the PPS4/1 Series. Are they the ones you are interested in?
>...
>> Hard to say. The chips I have all have inhouse numbers on them.
>> It sure does sound like the right stuff though. The chips are
>> all 42 pin spider chips.
>
>There's no detail about the packaging, but only one chip has 42 pins.
>The MM78 (and MM78LA) is listed as "42-pin quad in line". That chip
>has 2k of 8-bit ROM, 128x4 bit RAM and 31 I/O lines. Instructions
>are 8 bits wide, but the ALU and memory are 4-bit. Maximum clock
>frequency is 100kHz.
>
>--
>John Honniball
>coredump(a)gifford.co.uk
>
Hi John
That would most likely be part of what I'm looking for.
"42-pin quad in line" sounded like how they might describe
the spider chips. I suspect that this is what most of the
IC's are on this unit.
Dwight
>From: "William Donzelli" <aw288(a)osfn.org>
>
>> My favorite on the opposite end, is a random bit stream produced by
>> using the pulses from a geiger counter (and associated radioactive
>> material) to clock a long shift register. It's well-discussed, but I'm
>> not sure anyone ever produced one.
>
>I *think* some military crypto gear did things link this, but I am not
>sure.
>
>I know that AT&T once marketted a true random bitstream chip using a bunch
>of unstable oscillators.
>
>William Donzelli
>aw288(a)osfn.org
>
>
Hi
It has been shown that if you loosely couple three oscillators
they will produce chaotic periods. I've also seen that when
a zener diode is around 7.2V it is especially noisy. This
has been used to produce many types of random noise, including
white and pink noise for special purposes. Most silicon transistors
will zener in this region if back biased, base to emitter. I
ones made a wave sound simulator using both the zener and
the oscillator principles.
Dwight
I fired up an Altair and found it didn't behave as it should (tested
with MITs and Polymorphic CPU cards.) Doing an "Examine" does not load
the switch settings into the program counter. Doing an "Examine Next"
seems to increment the program counter by 3. The preceeding was done
with and without a memory card. I tried the "Deposit" but had no way to
see what I was doing since the switch settings apparently weren't being
loaded. Finally, the "Deposit Next" increments the LEDs. One other
strangeness, when I connect the Data Display cable to the MITS card, the
"Stop" switch ceases to function although the "Start" seems to work
fine.
I do have the schematics and will start to dig into it later this
morning. BUT, I was hoping to short circuit some of the troubleshooting
time if someone on the list has experienced something like this :).
Thanks!
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it is described as
Cabletron MMAC-M8FNB chassis populated with 1 MODMIM-4, 1 CRM-2E
router, 1 TPRMIM-36 10MB ethernet and an EMM-E6 module.
Is this something that might be of interest? All Google seems to find is
people selling them.
- --
Collector of vintage computers http://www.ncf.ca/~ba600
Open Source Weekend http://www.osw.ca
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Hi Everyone,
Does anybody have an extra side stand for the IBM AT that they would
part with? I have never seen one, but it's my understanding that IBM
made one for the AT, but most people didn't use them.
I'm willing to pay shipping plus a reasonable amount for one in good shape.
Chad Fernandez
Michigan, USA
Hi Chandra,
I believe there is a project called "altogether" by Eric Smith which is an
attempt to emulate the Alto under Unix and X-Windows.
http://altogether.brouhaha.com/
- John
jlewczyk(a)speakeasy.net
Sellam Ismail (vcf(a)siconic.com) wrote:
> Does anyone know what was the first computer to have a built-in real-time
> clock?
I take it you mean non-volatile clock like the M48T02 RTC chips on the early
SUN-4 machines.
The reason why there is a difference, is that most operating systems
(esp. those that have preemptive schedulers) need a regular timer
interrupt. So they use that interrupt for their time-of-day clock. This
method is generally accurate and convenient since mainframes were not
likely to be switched off overnight.
Another advantage held by the early mainframes is that they were kept
in a stable environment, which meant that their clock keeping was pretty
good anyway.
The other reason why you don't actually want to read a time of day
clock while the OS is running is speed. Why waste time on I/O since the
OS can just keep the elapsed time variable updated with a single
instruction.
UNIX is a good example: when you boot, the OS goes to the RTC, reads
the current time and date and converts it to the UNIX time (seconds
since 00:00 Jan 1 1970 UTC). From that moment onwards, the OS is making
sure that this value is updated so that it is current. When you
actually ask for the time, the system (actually the C library) converts
the contents of its time-of-day memory location into the calendar date
that humans like to see. When you actually want to set the correct
time, the system will update its internal time-of-day memory location
*and* the RTC so that then next time the system boots, it will have the
correct time.
BTW, the original PCs did not have a non-volatile clock, which is why MSDOS
by default asks for the date and time every time you boot (assuming you
do not override it by creating a AUTOEXEC.BAT file).
Since many people mentioned various HP calculators and computers with
non-volatile clocks, I only want to mention the HP 59309A HP-IB Digital
Clock. This is an HP-IB device that returns the current time/date as
an ASCII string. SO if your computer did not have a non-volatile clock
you could easily add one.
**vp
