🚀 go-pugleaf

On 2018-03-29, Andreas Kohlbach <a...@spamfence.net> wrote:

> The YouTube channel of the University of Nottingham, better known as
> Computerphile, has published a short video about the IMSAI 8080 (next to
> the Altair in an earlier video)
> <https://www.youtube.com/watch?v=trf2Nb1mXIc> where they also mention
> that Matthew Broderick showed up with it in the 1983 movie War
> Games. Nothing new, but I enjoyed watching it. As all videos they come up
> with. :-)

I wanted one of those 9600-bps acoustic couplers.  :-)

I tried getting my IMSAI going last summer; the processor seemed to
act OK, but I suspect the boot ROM has decayed.  It appears to be
almost impossible to find either a 2708 or a programmer for it, 
but I've come across a hack that lets you use half of a 2716 instead.
I think I can find a listing of the ROM contents, so there's a chance
I could get it going - along with my H19 terminal and the model 35RO
Teletype I used as a printer - in my copious free time (hah!).

-- 
/~\  cgibbs@kltpzyxm.invalid (Charlie Gibbs)
\ /  I'm really at ac.dekanfrus if you read it the right way.
 X   Top-posted messages will probably be ignored.  See RFC1855.
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On 29 Mar 2018 23:10:26 GMT, Charlie Gibbs wrote:
>
> On 2018-03-29, Andreas Kohlbach <a...@spamfence.net> wrote:
>
>> The YouTube channel of the University of Nottingham, better known as
>> Computerphile, has published a short video about the IMSAI 8080 (next to
>> the Altair in an earlier video)
>> <https://www.youtube.com/watch?v=trf2Nb1mXIc> where they also mention
>> that Matthew Broderick showed up with it in the 1983 movie War
>> Games. Nothing new, but I enjoyed watching it. As all videos they come up
>> with. :-)
>
> I wanted one of those 9600-bps acoustic couplers.  :-)
>
> I tried getting my IMSAI going last summer; the processor seemed to
> act OK, but I suspect the boot ROM has decayed.

Boot rom? Pah! You key in your boot loader on the front panel switches. ;-)

> It appears to be almost impossible to find either a 2708 or a
> programmer for it, but I've come across a hack that lets you use half
> of a 2716 instead.  I think I can find a listing of the ROM contents,
> so there's a chance I could get it going - along with my H19 terminal
> and the model 35RO Teletype I used as a printer - in my copious free
> time (hah!).

Of course you could download a boot rom image, burn it to an eprom and go
from there.

But I never had an Altair or IMSAI. Only learned about their existence a
few years ago when diving into the history on vintage (home)
computers. Must have been an exciting time I totally missed. For once I
was way too you and also lived in the "wrong country". Suppose you had to
live in the US to even become aware of them back in the day.
-- 
Andreas

My random toughts and comments
https://news-commentaries.blogspot.com/

On 2018-03-30, Andreas Kohlbach <a...@spamfence.net> wrote:

> On 29 Mar 2018 23:10:26 GMT, Charlie Gibbs wrote:
>
>> On 2018-03-29, Andreas Kohlbach <a...@spamfence.net> wrote:
>>
>>> The YouTube channel of the University of Nottingham, better known
>>> as Computerphile, has published a short video about the IMSAI 8080
>>> (next to the Altair in an earlier video)
>>> <https://www.youtube.com/watch?v=trf2Nb1mXIc> where they also
>>> mention that Matthew Broderick showed up with it in the 1983 movie
>>> War Games. Nothing new, but I enjoyed watching it. As all videos
>>> they come up with. :-)
>>
>> I wanted one of those 9600-bps acoustic couplers.  :-)
>>
>> I tried getting my IMSAI going last summer; the processor seemed to
>> act OK, but I suspect the boot ROM has decayed.
>
> Boot rom? Pah! You key in your boot loader on the front panel switches. ;-)

I wish I could.  Unfortunately, depositing bytes into memory from the
front panel switches required a hardware hack that was only present
on the original RAM-4A boards.  I replaced them with a single board
that held 64K and ran _much_ cooler.

>> It appears to be almost impossible to find either a 2708 or a
>> programmer for it, but I've come across a hack that lets you use half
>> of a 2716 instead.  I think I can find a listing of the ROM contents,
>> so there's a chance I could get it going - along with my H19 terminal
>> and the model 35RO Teletype I used as a printer - in my copious free
>> time (hah!).
>
> Of course you could download a boot rom image, burn it to an eprom
> and go from there.

That's what I said - I have to even do a hack to burn an EPROM.
As for the boot ROM image, it's probably printed out on a
moldering piece of teletype paper somewhere in my files.

> But I never had an Altair or IMSAI. Only learned about their
> existence a few years ago when diving into the history on
> vintage (home) computers. Must have been an exciting time
> I totally missed. For once I was way too you and also lived
> in the "wrong country". Suppose you had to live in the US to
> even become aware of them back in the day.

It was a fun time.  Not sure whether I'd do it over again, but
it would be kind of neat to get the IMSAI running again and
driving that Teletype.  If I was really daring (and had tons
of time), I'd try to get those UNISERVO VI-C tape drives
working again.  A friend once hacked together an S-100
interface and managed to read a block of data from them
into his IMSAI.

-- 
/~\  cgibbs@kltpzyxm.invalid (Charlie Gibbs)
\ /  I'm really at ac.dekanfrus if you read it the right way.
 X   Top-posted messages will probably be ignored.  See RFC1855.
/ \  HTML will DEFINITELY be ignored.  Join the ASCII ribbon campaign!

On 2018-03-31, Andreas Kohlbach <a...@spamfence.net> wrote:

> On 31 Mar 2018 17:20:57 GMT, Charlie Gibbs wrote:
>
>> On 2018-03-30, Andreas Kohlbach <a...@spamfence.net> wrote:
>>
>>> On 29 Mar 2018 23:10:26 GMT, Charlie Gibbs wrote:
>>>
>>>> I tried getting my IMSAI going last summer; the processor seemed to
>>>> act OK, but I suspect the boot ROM has decayed.
>>>
>>> Boot rom? Pah! You key in your boot loader on the front panel switches. ;-)
>>
>> I wish I could.  Unfortunately, depositing bytes into memory from the
>> front panel switches required a hardware hack that was only present
>> on the original RAM-4A boards.  I replaced them with a single board
>> that held 64K and ran _much_ cooler.
>
> I watched some videos on Youtube concerning the IMSAI. The author showed
> how to key in some code to jump start the system so he could load
> programs from punched tape or modern devices like an 8" floppy. *g*
> Cannot remember if this needed a spacial board.

The IMSAI took some shortcuts when displaying and alterming memory
through the front panel.  IIRC it tricked the 8080 chip into fetching
a byte as if it were an instruction, then somehow froze things and
displayed the byte on the lights.  Writing to memory required an
even weirder hack which needed special circuitry on the memory board
itself.  This circuitry was present on the original IMSAI RAM-4A
boards, but nobody else duplicated it.  Thus if you upgraded to
other memory boards, you could still read from memory via the
front panel, but you couldn't deposit data into memory.

-- 
/~\  cgibbs@kltpzyxm.invalid (Charlie Gibbs)
\ /  I'm really at ac.dekanfrus if you read it the right way.
 X   Top-posted messages will probably be ignored.  See RFC1855.
/ \  HTML will DEFINITELY be ignored.  Join the ASCII ribbon campaign!

On 3/30/2018 3:48 PM, Andreas Kohlbach wrote:
>
 >        [snip...]           [snip...]            [snip...]
 >
> But I never had an Altair or IMSAI. Only learned about their existence a
> few years ago when diving into the history on vintage (home)
> computers. Must have been an exciting time I totally missed. For once I
> was way too you and also lived in the "wrong country". Suppose you had to
> live in the US to even become aware of them back in the day.
> 

"Back in the day" is I do *not* know when.   If "back in the day" is the 
early 1980's, check out these links:


https://en.wikipedia.org/wiki/Category:German_computer_magazines

https://www.pinterest.com/pin/121597258659009359/

-- 
numerist at aquaporin4 dot com

On 31/03/2018 22:36, Charlie Gibbs wrote:
> 
> The IMSAI took some shortcuts when displaying and alterming memory
> through the front panel.  IIRC it tricked the 8080 chip into fetching
> a byte as if it were an instruction, then somehow froze things and
> displayed the byte on the lights.

A similar technique was used by John Miller-Kirkpatrick (RIP) in
his SCAMPI design based on the SC/MP microprocessor.

The "somehow freezing" is using the delaying input on memory accessing
to allow memories which are slower than the micros bus timing to be used
and holding the signal indefinitely until the next byte. This is only
good on static logic designs such as the Intel chips and not possible
on dynamic logic chips such as the Motorola chips.

What happens is this, the micro resets and starts to fetch instructions
from byte zero onwards. However, the response to the fetch is to assert
the delay pin to extend the memory access. Then, using the front panel
switches the byte to be written to address zero is set up, the read line
changed to a write, and then a NOP is electronically placed on the bus,
the delay released and the micro then tries to fetch from address one, 
and so on and so forth.

Not sure that's a sufficiency, but it's only off-the-cuff!

On Sat, 31 Mar 2018 17:25:25 -0500, Charles Richmond
<nume...@aquaporin4.com> wrote:

>On 3/30/2018 3:48 PM, Andreas Kohlbach wrote:
>>
> >        [snip...]           [snip...]            [snip...]
> >
>> But I never had an Altair or IMSAI. Only learned about their existence a
>> few years ago when diving into the history on vintage (home)
>> computers. Must have been an exciting time I totally missed. For once I
>> was way too you and also lived in the "wrong country". Suppose you had to
>> live in the US to even become aware of them back in the day.
>> 
>
>"Back in the day" is I do *not* know when.   If "back in the day" is the 
>early 1980's, check out these links:
>
>
>https://en.wikipedia.org/wiki/Category:German_computer_magazines
>
>https://www.pinterest.com/pin/121597258659009359/

Altair was mid '70s.  It was the first attempt at a personal computer
that (a) was actually affordable, (b) was actually potentially useful,
and (c) got any press attention.  Just about everybody with an
interest in computers knew about it.

On Saturday, March 31, 2018 at 8:49:09 PM UTC-4, J. Clarke wrote:

> Altair was mid '70s.  It was the first attempt at a personal computer
> that (a) was actually affordable, (b) was actually potentially useful,
> and (c) got any press attention.  Just about everybody with an
> interest in computers knew about it.

Would you know what kind of applications people ran on it?  The 
following article is very interesting, but does not talk about 
applications:
https://en.wikipedia.org/wiki/Altair_8800

It appears that to do anything beyond hobbyist work, a person needed
to purchase additional memory, interface boards, and a Teletype to
provide I/O (entering programs by switches was very tedious).  It
would seem the price of a 'complete' system would be about $3,000-4,000
in today's dollars, about two year's worth of time-sharing service.

hanc...@bbs.cpcn.com writes:
>On Saturday, March 31, 2018 at 8:49:09 PM UTC-4, J. Clarke wrote:
>
>> Altair was mid '70s.  It was the first attempt at a personal computer
>> that (a) was actually affordable, (b) was actually potentially useful,
>> and (c) got any press attention.  Just about everybody with an
>> interest in computers knew about it.
>
>Would you know what kind of applications people ran on it?  The 
>following article is very interesting, but does not talk about 
>applications:
>https://en.wikipedia.org/wiki/Altair_8800
>
>It appears that to do anything beyond hobbyist work, a person needed
>to purchase additional memory, interface boards, and a Teletype to
>provide I/O (entering programs by switches was very tedious).  It
>would seem the price of a 'complete' system would be about $3,000-4,000
>in today's dollars, about two year's worth of time-sharing service.

$3,000-$4,000 in 1977 dollars, you mean.

http://www.lurndal.org/images/altair_pricelist_pg1.jpg
http://www.lurndal.org/images/altair_pricelist_pg2.jpg

On Mon, 2 Apr 2018 13:49:04 -0700 (PDT), hanc...@bbs.cpcn.com wrote:

>On Saturday, March 31, 2018 at 8:49:09 PM UTC-4, J. Clarke wrote:
>
>> Altair was mid '70s.  It was the first attempt at a personal computer
>> that (a) was actually affordable, (b) was actually potentially useful,
>> and (c) got any press attention.  Just about everybody with an
>> interest in computers knew about it.
>
>Would you know what kind of applications people ran on it?  The 
>following article is very interesting, but does not talk about 
>applications:
>https://en.wikipedia.org/wiki/Altair_8800
>
>It appears that to do anything beyond hobbyist work, a person needed
>to purchase additional memory, interface boards, and a Teletype to
>provide I/O (entering programs by switches was very tedious).  It
>would seem the price of a 'complete' system would be about $3,000-4,000
>in today's dollars, about two year's worth of time-sharing service.

The Altair was an S-100 machine.  It could be made to do just about
anything that was within the capabilities of the 8080.  How much it
cost to trick it out depended on how much sweat equity you were
willing to put in and how good a scrounger you were.  Getting it fully
configured to where it was a reasonable alternative to a PDP-11 could
cost a bit if you were buying all the parts preassembled, but it would
still be a lot less than DEC would ask for a similar configuration in
the PDP-11.

As for applications, CP/M was available very early and from there a
wide range of applications became available.