Nope, the clock you see was divided by 2.
the board had two clocks one provided the 2mhz 2phase
12V clock for the 8080 the other was for other clocked parts.
Allison
-----Original Message-----
From: Richard Erlacher <edick(a)idcomm.com>
To: classiccmp(a)classiccmp.org <classiccmp(a)classiccmp.org>
Date: Sunday, September 30, 2001 6:15 PM
Subject: Re: 8080 vs. 8080A
>The half-dozen or so I8020/4 boards I have all have i8080A CPU's in
them, and
>each is clocked at 4.(something very small) MHz, IIRC. Are you saying
that
>Intel ran these >1 MHz above spec? I've also seen numerous applications
in
>which they were driven at the color burst frequency from some harmonic
of that.
>
>Dick
>
>----- Original Message -----
>From: "ajp166" <ajp166(a)bellatlantic.net>
>To: <classiccmp(a)classiccmp.org>
>Sent: Sunday, September 30, 2001 2:31 PM
>Subject: Re: 8080 vs. 8080A
>
>
>> Wrong!
>>
>> The I8080A is AS fast as the i8080. the i8080A-1 is faster but not
twice
>> as the fastest 8080[A] was only 3mhz and hte standard part was 2mhz.
>>
>> Allison
>>
>> -----Original Message-----
>> From: John Galt <gmphillips(a)earthlink.net>
>> To: classiccmp(a)classiccmp.org <classiccmp(a)classiccmp.org>
>> Date: Sunday, September 30, 2001 3:57 PM
>> Subject: Re: 8080 vs. 8080A
>>
>>
>> >"The i8080A is essentially twice as fast as the
>> > standard i8080 and COULD be used more easily with low-power logic
since
>> its
>> >demands aren't as stringent".
>> >
>> >Ok, that's a good start.
>> >
>> >But, I don't think "low power" TTL (transistor transistor logic) had
>> >anything to do with the complexity of the code being executed on the
>> chip.
>> >True? I had assumed
>> >that the references to the 8080 only being compatible
>> >with "low-power TTL" and the 8080A being compatible
>> >with "standard TTL" had something to do with the support chips (Ram,
>> clock,
>> >etc) that could be used with the 8080 vs. the 8080A.
>> >
>> >Since I'm new to this mail list, let me explain why I would
>> >show up here and ask such a question to begin with.
>> >
>> >I'm a chip collector. I am trying to document the differences
between
>> the
>> >different early Intel microprocessors. Not worried about massive
>> detail,
>> >just the major differences (PMOS, vs. NMOS, vs.
>> >HMOS, clock speed, transistor count, etc).
>> >
>> >The only microprocessor that I don't have a good handle
>> >on is the 8080 and the difference between the 8080 and 8080A.
>> >
>> >I also know that the 8080 was introduced sometime
>> >around April 1974. I have not been able to find an
>> >introduction date for the 8080A. Was it introduced at
>> >the same time? Does anyone know?
>> >
>> >I also need an Intel C8080 or C8080-8 for my
>> >collection. If you have one, I want it. I have been looking
>> >for one for months and have not been able to find one.
>> >If you have either of these chips in good condition
>> >(no desoldered parts wanted), I'm offering 400.00
>> >for the C8080-8 and 500.00 for a C8080.
>> >
>> >If you need a replacement for the C8080 or C8080-8 you sell me, I'll
>> GIVE
>> >you a D8080A free as part of the
>> >deal.
>> >
>> >----- Original Message -----
>> >From: "Richard Erlacher" <edick(a)idcomm.com>
>> >To: <classiccmp(a)classiccmp.org>
>> >Sent: Sunday, September 30, 2001 1:21 PM
>> >Subject: Re: 8080 vs. 8080A
>> >
>> >
>> >> This makes no sense at all, though it may be because I'm
>> misinterpreting
>> >the way
>> >> in which you've put it.
>> >>
>> >> I have Intel boards that come in versions with the i8080 and also,
>> >> optionally,with the i8080A, and, aside from the clock frequency and
>> memory
>> >> access times, they're identical. The i8080A is essentially twice
as
>> fast
>> >as the
>> >> standard i8080 and COULD be used more easily with low-power logic
>> since
>> >its
>> >> demands aren't as stringent.
>> >>
>> >> The i8080A will, AFAIK, replace the i8080 in all applications
without
>> ill
>> >> effects.
>> >>
>> >> BTW, please turn off "rich-text" mode in your email editor when you
>> >compose
>> >> messages for this group, as some folks' mail readers can't
interpret
>> the
>> >> rich-text/HTML format.
>> >>
>> >> Dick
>> >> ++++++++++++++++++++++++++++++++++++++
>> >> ----- Original Message -----
>> >> From: John Galt
>> >> To: classiccmp(a)classiccmp.org
>> >> Sent: Sunday, September 30, 2001 10:17 AM
>> >> Subject: 8080 vs. 8080A
>> >>
>> >>
>> >> Can anyone here describe the technical differences between
>> >> an Intel 8080 and Intel 8080A CPU?
>> >>
>> >> The ONLY ref. I have been able to find seems to indicate that there
>> was a
>> >bug in
>> >> the 8080 and as a result it would only work with low power TTL?
>> >>
>> >> The problem was fixed in the 8080A and it would work with standard
>> TTL?
>> >>
>> >> Does this make sense to anyone?
>> >>
>> >> Could anyone put this into laymans terms for me?
>> >>
>> >> Thanks,
>> >>
>> >> George Phillips - gmphillips(a)earthlink.net
>> >>
>> >
>>
>>
>
On Sep 29, 23:32, Jeffrey S. Sharp wrote:
> Yes, I'm actually going to ask a question about two's complement
> arithmetic! I feel quite stupid for mailing this, but I just can't
figure
> it out. And believe it or not, it really does have something to do with
> classic computing. All right, here goes...
>
> While I was in class Thursday [...] I created the following table:
[ snip ]
> Note that the C and V flags behave differently in each half. This is
very
> disturbing, since I'm fairly certain that subtraction is implemented in
> many processors as adding a negated subtrahend (ergo, I should see no
> difference in the flags). What have I done wrong in my table?
Firstly, you're assuming (on the left) that "carry" is the same as
"borrow". Wrong! If you are subtracting, working the columns
right-to-left, a borrow from one column to the previous (on the right) is
balanced by adding the borrowed digit back to the subtrahend, so it gets
subtracted from the result, not added. This is the opposite of a carry.
That's why most of the "carry" flags you show in the left side of the
table are incorrect; they're actually "borrow" flags. If you think this is
confusing, try comparing the carry flags implemented in a Z80 and a 6502
(they do different things for subtractions!).
The other problem you have is with the overflow. It's not a problem with
signed vs unsigned numbers as some people have implied, it's with the order
you do things in. I assume you're setting the V (oVerflow) as the XOR of
the carry into the MSB and the carry out of the MSB. Well, this is true,
but for it to work with pathological cases you don't do the full two's
complement process before the addition, but do it at the same time. One of
your cases is
Subtraction Equivalent Addition
AA-BB=CC CZSV AA+BB=CC CZSV
01 10 11 x.xx 01 10 11 ..x.
The difficulty is that binary 10 is its own complement. However, you'll
get the right answer if you say that "A - B" is the same as "A + inv(B) +
1" where "inv(B)" is the ones-complement of B. "inv(10)" is "01". Now add
"01" + "01" + "1" in a single step. You'll find the carry out of the MSB
is a "0", of course, but the carry into the MSB is a "1". Therefore V = 1
xor 0 = 1. Which is what we hope!
However, if you say that "A - B" is the same as "A + cpl(B)" where "cpl(B)"
is the twos-complement of "B", ie you do "inv(B) + 1" ahead of the rest of
the addition -- as you did -- you'll add "01 + 10" in a separate step.
Then you'll find the carry into the MSB is now a "0", and 0 xor 0 = 0,
implying no overflow. Wrong answer!
That's one of the reasons that ALU designers don't usually implemetn a
2-stage complement-and-add for subtraction, but instead do it with a
single-stage invert-add-xor operation (the xor being the addition of the
extra "1" which makes the invert arithmetically equivalent to
2s-complement).
--
Pete Peter Turnbull
Network Manager
University of York
Wrong!
The I8080A is AS fast as the i8080. the i8080A-1 is faster but not twice
as the fastest 8080[A] was only 3mhz and hte standard part was 2mhz.
Allison
-----Original Message-----
From: John Galt <gmphillips(a)earthlink.net>
To: classiccmp(a)classiccmp.org <classiccmp(a)classiccmp.org>
Date: Sunday, September 30, 2001 3:57 PM
Subject: Re: 8080 vs. 8080A
>"The i8080A is essentially twice as fast as the
> standard i8080 and COULD be used more easily with low-power logic since
its
>demands aren't as stringent".
>
>Ok, that's a good start.
>
>But, I don't think "low power" TTL (transistor transistor logic) had
>anything to do with the complexity of the code being executed on the
chip.
>True? I had assumed
>that the references to the 8080 only being compatible
>with "low-power TTL" and the 8080A being compatible
>with "standard TTL" had something to do with the support chips (Ram,
clock,
>etc) that could be used with the 8080 vs. the 8080A.
>
>Since I'm new to this mail list, let me explain why I would
>show up here and ask such a question to begin with.
>
>I'm a chip collector. I am trying to document the differences between
the
>different early Intel microprocessors. Not worried about massive
detail,
>just the major differences (PMOS, vs. NMOS, vs.
>HMOS, clock speed, transistor count, etc).
>
>The only microprocessor that I don't have a good handle
>on is the 8080 and the difference between the 8080 and 8080A.
>
>I also know that the 8080 was introduced sometime
>around April 1974. I have not been able to find an
>introduction date for the 8080A. Was it introduced at
>the same time? Does anyone know?
>
>I also need an Intel C8080 or C8080-8 for my
>collection. If you have one, I want it. I have been looking
>for one for months and have not been able to find one.
>If you have either of these chips in good condition
>(no desoldered parts wanted), I'm offering 400.00
>for the C8080-8 and 500.00 for a C8080.
>
>If you need a replacement for the C8080 or C8080-8 you sell me, I'll
GIVE
>you a D8080A free as part of the
>deal.
>
>----- Original Message -----
>From: "Richard Erlacher" <edick(a)idcomm.com>
>To: <classiccmp(a)classiccmp.org>
>Sent: Sunday, September 30, 2001 1:21 PM
>Subject: Re: 8080 vs. 8080A
>
>
>> This makes no sense at all, though it may be because I'm
misinterpreting
>the way
>> in which you've put it.
>>
>> I have Intel boards that come in versions with the i8080 and also,
>> optionally,with the i8080A, and, aside from the clock frequency and
memory
>> access times, they're identical. The i8080A is essentially twice as
fast
>as the
>> standard i8080 and COULD be used more easily with low-power logic
since
>its
>> demands aren't as stringent.
>>
>> The i8080A will, AFAIK, replace the i8080 in all applications without
ill
>> effects.
>>
>> BTW, please turn off "rich-text" mode in your email editor when you
>compose
>> messages for this group, as some folks' mail readers can't interpret
the
>> rich-text/HTML format.
>>
>> Dick
>> ++++++++++++++++++++++++++++++++++++++
>> ----- Original Message -----
>> From: John Galt
>> To: classiccmp(a)classiccmp.org
>> Sent: Sunday, September 30, 2001 10:17 AM
>> Subject: 8080 vs. 8080A
>>
>>
>> Can anyone here describe the technical differences between
>> an Intel 8080 and Intel 8080A CPU?
>>
>> The ONLY ref. I have been able to find seems to indicate that there
was a
>bug in
>> the 8080 and as a result it would only work with low power TTL?
>>
>> The problem was fixed in the 8080A and it would work with standard
TTL?
>>
>> Does this make sense to anyone?
>>
>> Could anyone put this into laymans terms for me?
>>
>> Thanks,
>>
>> George Phillips - gmphillips(a)earthlink.net
>>
>
On Sep 30, 12:06, Jeffrey S. Sharp wrote:
> On Sun, 30 Sep 2001, Pete Turnbull wrote:
>
> > you're assuming (on the left) that "carry" is the same as "borrow".
>
> This works itself out exactly like that below.
>
> > However, you'll get the right answer if you say that "A - B" is the
> > same as "A + inv(B) + 1" where "inv(B)" is the ones-complement of B.
>
> Bingo! That fixed it:
>
> * I get correct overflow flag values.
>
> * The correct borrow flag value is the opposite of the carry out of the
> addition.
Did you notice that in a few cases, your carry wasn't the opposite of the
borrow, in the original table? But it sorted itself out so that it was
consistent once you used "A + inv(B) + 1" on the right hand side.
> Now what's disturbing is that the same wrong ideas that I was taught were
> taught to an entire roomful of college students a few years ago, by a
> professor in the School of Electrical and Computer Engineering.
Maybe part of the confusion arises because many processors (including the
8080) complement the carry flag at the end of a subtraction, so that it can
be used directly as a "borrow" flag in multibyte subtractions. Others
(like the 6502) don't do that.
The confusion over the overflow usually arises because people are told that
adding the two's complement of a number is equivalent to subtraction.
That's not so much "wrong" as "incomplete". As you've seen, it's
arithmetically but not logically equivalent. If you combine the
carry-into-MSB from the compliment op with the carry-into-MSB from the
subsequent addition, they would be logically equivalent as well, but you'd
also need to do this for the carry flag otherwise subtracting 0 tends to
give the wrong result :-)
Since you're thinking about 2's complements, and I've mentioned you could
combine the carry-in from the complement operation with the carry-in in the
addition, you might like to think about different ways of performing the
2's complement. The way usually explained is "invert the bits and add a
1". There's another common way: find the *rightmost* '1' in the number.
Invert every bit to its left. Done. Now where's the carry in that? Oh,
and you need to use a particular search order to find the "rightmost 1".
> Thanks for the help.
You're welcome. It took me a few minutes to realise what was wrong, so it
was an interesting exercise :-)
--
Pete Peter Turnbull
Network Manager
University of York
I hope this information helps.
>So what (please be sepecific, and include details, e.g. how COMPLETE the stuff
>is, i.e. manuals, drivers, etc.) APPLE][ stuff do you have?
I have working II+, IIe and a IIgs computer with 1.5 meg upgrade board. I have
alot of original diskettes and manuals for most of the common Apple stuff.
I have
one or two of the original red books, joysticks, floppy drives, etc. I
also have
a John Bell Engineering voice synth card with diskettes and a BAL-500 eprom
programmer.
I'm not an
>APPLE-freak, but in order to do a couple of 1-time tasks, I need a couple of
>things. I'm also interested in S-100 cards, particularly if they're
>documented
>and complete with software, but I don't need backplanes or boxes, nor do I
>need
I do have a few S100 cards. Mostly they're undocumented static and dynamic
memory boards (which are easy to figure out). However, I do have a MM103
modem and documentation but no software and the S100 hayes micromodem with
the direct connect coupler interface. I also have a SMB multifunction card
in bad
shape and one or two Diskjockey IIds if I recall, with documentation but no
software.
I have a bunch of 8" diskettes with Xerox 820-II stuff on them including
boot disks.
>8" FD drives, as I have plenty.
>
>If you have the apple interface for that Xebec HDD, I'd be interested in that,
>as well, maybe, depending on how complete it is.
>
The Xebec does include the interface and driver diskettes but no documentation.
However, I was able to easily figure it out. Mostly if you just plug it
into slot#5
and do a pr#5 after booting, it'll boot.
>let me know, plz
>
>regards,
>
>Dick
>
>----- Original Message -----
>From: "Anthony Clifton - Retrocomputing.com" <vaxcat(a)retrocomputing.com>
>To: <classiccmp(a)classiccmp.org>
>Sent: Sunday, September 30, 2001 10:47 AM
>Subject: Possibility of Classic Computing Garage Sale/Auction
>
>
>>
>> So, here's the deal. From time to time, I get the itch to collect classic
>> computing
>> stuff. I collect a bunch of stuff, pile it up in my house and then the
>> itch is scratched
>> and I forget about it for a while.
>>
>> What compels me to do this I don't pretend to understand. But the simple
>> fact is that
>> most of you are doing such a good job collecting, restoring and preserving
>> this stuff
>> that there's just no need for me to do it. In other words, because I'm
>> pursuing my
>> own interests which take alot of space, the time has come to choose either
>> to be a
>> classic computer collector or not to be. (IE it's time to sh*t or get off
>> the pot.)
>>
>> Therefore, I'm considering sending ALL my classic computing stuff to live
>> with the
>> rest of you where it will be preserved and loved. This will free up ALOT
>> of space
>> in my house to pursue interests such as art and photography.
>>
>> And I'll get to see alot of smiling faces taking home treasures.
>>
>> Mind you, I'd like to get some money back out of this stuff but not
>> necessarily as
>> much as I'd get on Ebay.
>>
>> So I'm considering holding a garage sale/auction at my home the last weekend
>of
>> October in Des Moines, Iowa. More valuable items would be auctioned
>>over the
>> course of an hour or so while less valuable (more common) items would simply
>> be priced, haggled and sold.
>>
>> Stuff that would be sold or auctioned includes: Apple II stuff, Kaypro II,
>> Epson QX10, Green
>> screen monitors, Microvax II, Vaxstation 3100, Sun 3/60, 3/110s, Sun mono
>> monitors, mice, keyboards, books. I have a Cisco IGS router (now 10 years
>> old),
>> a livingston 10 port terminal server, a TIE S100 chassis, a Vector S100
>> business
>> computer with 8" hard disk in separate enclosure, around a dozen s100 cards,
>> macintosh plus and other macintosh equipment, an 8" drive in it's own
>> enclosure,
>> a Shugart SA800 bare drive, software, books and all kinds of miscellaneous
>> bits of
>> hardware and software. I also have a 9 track streaming tape drive that
>> goes with
>> the Microvax II.
>>
>> I also have an old tektronix scope with aluminum rolling cart, a 19" dual
>width
>> bud rack (4' tall appox), a crusty Northstar chassis and some other
>> miscellaneous
>> ham radio and electronics equipment.
>>
>> Also, of note, I have a 19" color terminal (the Intelligent Systems Corp
>> unit I mentioned
>> a few months ago), a vt102 and 2 or 3 vt220s with keyboards. I also have a
>> Xebec 10 meg
>> hard disk for Apple II machines and other weird and bizarre stuff.
>>
>> As I say, although I want to get a few bucks out of the stuff, I also want
>> everything
>> to go. So I'm willing to haggle. This would send it all away in one big
>> shot for me,
>> which would be absolutely wonderful. It'd also make me feel alot better
>> than putting
>> stuff in a dumpster or sending it to Goodwill.
>>
>> So, essentially, what I'm looking for is this: If I were to hold this the
>> last Saturday
>> of October, how many people would be able to come or send another collector
>> on their
>> behalf? It would be in Des Moines, Iowa.
>>
>> Please send me an email if you would be able to attend and, if enough
>> people express
>> interest, I'll make specific plans and post them this week.
>>
>> Thanks and I hope everyone will see this as a positive thing and not be too
>> hard on me
>> for wanting to pursue my other interests.
>>
>> Anthony Clifton
>> Des Moines, Iowa
>>
>>
>>
> On September 29, Doug Salot wrote:
> > This weekend only in Orange County, CA:
> > AIM65
> > Dynabyte S-100
> > Rockwell Design Center
> > http://www.blinkenlights.com/classiccmp/aim65/design3.jpg
> > maybe some other stuff
> >
> > Preference goes to somebody who offers to haul it all away by noon Sunday.
> > Contact me by email for more info.
>
> Oh, how I'd love to get my grubby paws on that Dynabyte. :-|
I'd love to get the AIM65, but I'm not in Orange Counter. :-(
--
Eric Dittman
dittman(a)dittman.net
Check out the DEC Ethusiasts Club at http://www.dittman.net/
OK, I managed to dig out a VT100 out of storage. Of course the first path
I burrowed all the way back led to a VT103, so I had to dig an even more
difficult path.
Anyway, I've got it hooked up to the Intel 810e board I'm using for my
Desktop PDP-10 project. I've got Linux set so I can log in and do stuff.
The terminal seems happiest working at 9600. Under TOPS-10 V7.03 I can do
a DIR in a small directory and everything is fine, but if I run it in a big
directory such as SYS:, then I get slightly garbled data. Same thing if I
run a SYSTAT, it's garbled, especially the last part.
I'm not up on Serial stuff and I've seen simular results hooking up one of
my VT420's to Sun Sparc. Is the problem my cabling, or what? At the
moment I'm using what looks to be a LapLink cable (or the equivalent). For
the finished project I plan to build a custom cable.
Zane
--
| Zane H. Healy | UNIX Systems Administrator |
| healyzh(a)aracnet.com (primary) | OpenVMS Enthusiast |
| | Classic Computer Collector |
+----------------------------------+----------------------------+
| Empire of the Petal Throne and Traveller Role Playing, |
| PDP-10 Emulation and Zane's Computer Museum. |
| http://www.aracnet.com/~healyzh/ |
Simple, DEC terminals like to use Xon/Xoff flow control protocal
and will run ok without it if the baud rate is low enough.
You have two choices either hardware flowcontrol, or enable
and use xon/xoff. I'd suggest the latter as it's the common way
for DEC systems.
Allison
-----Original Message-----
From: Zane H. Healy <healyzh(a)aracnet.com>
To: classiccmp(a)classiccmp.org <classiccmp(a)classiccmp.org>
Date: Sunday, September 30, 2001 2:22 PM
Subject: Attaching a VT100 to a PC....
>OK, I managed to dig out a VT100 out of storage. Of course the first
path
>I burrowed all the way back led to a VT103, so I had to dig an even more
>difficult path.
>
>Anyway, I've got it hooked up to the Intel 810e board I'm using for my
>Desktop PDP-10 project. I've got Linux set so I can log in and do
stuff.
>The terminal seems happiest working at 9600. Under TOPS-10 V7.03 I can
do
>a DIR in a small directory and everything is fine, but if I run it in a
big
>directory such as SYS:, then I get slightly garbled data. Same thing if
I
>run a SYSTAT, it's garbled, especially the last part.
>
>I'm not up on Serial stuff and I've seen simular results hooking up one
of
>my VT420's to Sun Sparc. Is the problem my cabling, or what? At the
>moment I'm using what looks to be a LapLink cable (or the equivalent).
For
>the finished project I plan to build a custom cable.
>
> Zane
>--
>| Zane H. Healy | UNIX Systems Administrator |
>| healyzh(a)aracnet.com (primary) | OpenVMS Enthusiast |
>| | Classic Computer Collector |
>+----------------------------------+----------------------------+
>| Empire of the Petal Throne and Traveller Role Playing, |
>| PDP-10 Emulation and Zane's Computer Museum. |
>| http://www.aracnet.com/~healyzh/ |
On Sep 30, 10:46, Zane H. Healy wrote:
> Anyway, I've got it hooked up to the Intel 810e board I'm using for my
> Desktop PDP-10 project. I've got Linux set so I can log in and do stuff.
> The terminal seems happiest working at 9600. Under TOPS-10 V7.03 I can
do
> a DIR in a small directory and everything is fine, but if I run it in a
big
> directory such as SYS:, then I get slightly garbled data. Same thing if
I
> run a SYSTAT, it's garbled, especially the last part.
Sounds like handshaking, or rather, lack of it. I'd guess the terminal can
keep up for a while, but there comes a point where it has to scroll or
something, it sets the handshake to tell the other end to wait a moment,
but the other end doesn't, and a character or a few get dropped or garbled
while the terminal does its housekeeping. Have you got the same kind of
handshaking set up at both ends (ie both software XON/XOFF, or both CTS/RTS
or both DTR/DSR)? Usually VTs want to use XON/XOFF.
--
Pete Peter Turnbull
Network Manager
University of York
