Since this is about 8080/8080A the answer is fairly complex and simple
at the same time.
The 8080A had improved drive (not that much better) and improved interupt
timing. There were a few other minor differences of no real consequence.
was a bear with regard to DMA (hold/) and the 8080A was slightly better.
were that much fun to work with. For non-DMA designs the difference is
Both worked fine wtih Standard TTL _IF_ you followed fanout rules and
buffered things correctly.
From: Russ Blakeman <rhblakeman(a)kih.net>
To: classiccmp(a)classiccmp.org <classiccmp(a)classiccmp.org>
Date: Sunday, September 30, 2001 2:04 PM
Subject: RE: 8080 vs. 8080A
>Hadn't heard anything of an 8088/86 series bug but I know there's a 32
>applications lockup problem in some 386DX-16's and the well known
>point math problem in the original Pentium series.
> -----Original Message-----
> From: owner-classiccmp(a)classiccmp.org
>[mailto:email@example.com]On Behalf Of John Galt
> Sent: Sunday, September 30, 2001 11:18 AM
> To: classiccmp(a)classiccmp.org
> 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
>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?
> George Phillips - gmphillips(a)earthlink.net
After a few years of searching, I finally have a Wang 2200 computer (2200-T
style CPU, to be exact). Parts of it have been arriving from Dallas for
the past four months. The last piece arrived yesterday, the 2226
Unfortunately, the monitor just doesn't sync at all. Not having worked a
whole lot with video, I was hoping someone could steer me in the right
direction. I'll explain what I know so far.
First, this monitor, cable, and CPU were all part of a set -- I'm not
mixing and matching. Supposedly the video was fine when it left Dallas a
week or two ago.
The video goes from the CPU to the monitor over a single coax and has
composite sync. Video is baseband monochrome.
There are a couple hidden pots that can be twiddled, and I have, but the
best I can do is get it to a slow roll/tear. It is an impossible task as
just thermal drift causes the screen to wander. Neither vsync nor hsync
appears to work at all. At first I thought I just would have to tweak the
H & V pots into the lock range of the PLL that controls the sync but there
appears to be no locking zone.
I got a standard monitor that I use with my Sol and hooked it up. The
screen rolled wildly. By adjusting the H & V controls on that monitor, I
could get it to sync both axes, but the video was not readable -- it was
locking to some multiple/submultiple so the image was stable but not
coherent. Thus it seems to rule out the unlikely case that the original
monitor is OK and the video card is putting out signal but no sync.
So then I broke out my crappy scope that I picked up a hamfest, but which
is good enough for this job. I measured some timings. Interestingly, the
scope has TV V sync and TV H sync trigger modes; both worked properly to
lock the signal. Thus the timing is close enough to normal video for the
scope to think it was OK.
Timings below are as good as I can measure with this scope; 5% error
wouldn't be unlikely. I've put in square brackets the figure for normal US
television timing (from a web page that I just looked up)
vertical period: ~16.8 ms/frame [ 1/60 = 16.67 ]
v blanking: 4 scan lines
v front porch: 17 scan lines
v back porch: couldn't trigger it in a way to count them
v active: there are 24 rows of text, each on 11 scan lines, or 264 scans, =
horizontal period: 58 us [63.5]
h sync: 2 us [4.7]
h front porch: 7 us [4.7]
h video: 47 us [52.6]
h back porch: 3.5 us [1.5]
dc level: 0.7v
video white; 1.4 v
[ignore the voltages somewhat -- I was measuring them using a
high-impedance scope probe and a properly terminated coax would probably
lower those figures]
So here are my specific questions; if you have any thoughts and have read
this far, don't limit your responses to these questions, though.
1) Doesn't is seem odd that neither H nor V sync lock? What would cause
both to go out at the same time during shipment?
2) Doesn't it seem odd that the timing is pretty close to nominal but
my 2nd monitor can lock but not get a proper picture?
3) Any thoughts about what I should try next?
I have no schematics or technical docs for any of this.
Thanks for any ideas, even crackpot ones.
Jim Battle == frustum(a)pacbell.net
On September 30, Absurdly Obtuse wrote:
> it wouldn't surprise me if there were some people who just copied IBM
> BIOS, but slipped through the cracks of the IBM copyright enforcement
Indeed, I did exactly this with my first XT clone, built from a kit
with a bare PCB...
On September 30, Jeffrey S. Sharp wrote:
> 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.
Those who can, do...
I happened upon an older message/discussion about the PolyMorphic systems.
I have a lot of that stuff - including many of the user's groups
newsletters/original software/manuals, etc. I built mine in 1975 or 1976.
It still works but I never used the original toaster case. You indicated
that you could use some of the source code. Seems to me that I have some of
that in machine/assy language.
If you'd like to chat - e-mail me.
I have a Dawn VME 3 to 2 Adapter version 5 (Model: SUN9U400/6U-4) that I
no longer want. As a bonus you get the Imaging Technology Inc. card in it
too. There are no model numbers on this card but I am guessing it is some
sort of frame grabber.
Collector of old computers: http://www.heydon.org/kevan/collection/
I found an IBM 5150 at a thrift store the other day. I don't usually pay
much attention to PeeCee's, but the price of this one was about right--
$3.50 complete with dual floppies and monochrome monitor.
I don't have any boot disks for PC's this old. When I initially turned it
on, it would start up BASIC, which apparently is in ROM on these machines.
Lately, it hangs on a rapidly flashing left cursor, sometimes moving to a
rapidly flashing cursor at the top middle of the monitor.
Anybody know what causes this? Power supply? Video card? Loose chip?
What's the deal with the BASIC in ROM on these machines? Any other early
PeeCee's have this feature?
Bel Air, MD
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 got bored and decided to pass the time by
verifying that A-B=A+(-B) in two's complement binary arithmetic, using an
imaginary machine with a word size of 2 bits. I created the following
Subtraction Equivalent Addition
AA-BB=CC CZSV AA+BB=CC CZSV
01 01 00 .x.. 01 11 00 xx..
01 00 01 .... 01 00 01 ....
01 11 10 x.xx 01 01 10 ..xx
01 10 11 x.xx 01 10 11 ..x.
00 01 11 x.x. 00 11 11 ..x.
00 00 00 .x.. 00 00 00 .x..
00 11 01 x... 00 01 01 ....
00 10 10 x.xx 00 10 10 ..x.
11 01 10 ..x. 11 11 10 x.x.
11 00 11 ..x. 11 00 11 ..x.
11 11 00 .x.. 11 01 00 xx..
11 10 01 .... 11 10 01 x..x
10 01 01 ...x 10 11 01 x..x
10 00 10 ..x. 10 00 10 ..x.
10 11 11 x.x. 10 01 11 ..x.
10 10 00 .x.. 10 10 00 xx.x
The left half iterates through all possible subtractions, which were each
performed by hand by binary subtraction. The results and the states of
the machine's flags (Carry/borrow, Zero, Sign, oVerflow), are shown.
The right half contains the same subtractions, this time done by adding by
hand the minuend and the two's complement of the subtrahend.
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?
Jeffrey S. Sharp
"Iggy Drougge" wrote:
> I'm sory, but the URL goes to a "restricted area".
You just need to copy and paste the rest of the link:
> Nintendo produced a disk drive for the Famicom/NES
These are the only disk drives I have that are battery
powered - 6 "C" cells each.
@ home in Poulsbo, WA
Analog Computer Online Museum and History Center