More questions!

History and Preservation Issues

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Floopy
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More questions!

Postby Floopy » Wed Jan 24, 2018 7:08 pm

Hello everyone

I don't' know if this is the right place to put this.

More questions!

I'm going to be teaching a short class on 1980's computers. I'm mostly showing a demonstration, but I've been asked to talk a little bit about the internals.
Here's what I know so far.
If I have anything wrong is wrong CORRECT ME!
Baord.jpg

board.jpg

A few questions:
#1: is the VIC-20s clock a 555 timer, I wouldn't think so?
#2: the C64 and the VIC-20 both run at 1.023Mhz?
#3: how many VICs where sold?
#4: What is the speed of the tape drive? (Ex: 200 Bits per second)
#5: What is the difference between memory oriented architecture and register oriented architecture in CPUs.
#6: What are the main uses computers had in the 80s

Thank you.
-Floopy

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Floopy
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Re: More questions!

Postby Floopy » Wed Jan 24, 2018 7:09 pm

These are not my motherboards I took the pictures from online. They are the same type though.
-Floopy

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orion70
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Re: More questions!

Postby orion70 » Thu Jan 25, 2018 6:35 am

I'm not a techie but...
Floopy wrote:#6: What are the main uses computers had in the 80s

The answer is...
viewforum.php?f=10
:)

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srowe
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Re: More questions!

Postby srowe » Thu Jan 25, 2018 7:27 am

Floopy wrote:#2: the C64 and the VIC-20 both run at 1.023Mhz?


No, it varies between system, see http://www.lemon64.com/forum/viewtopic.php?t=36751

norm8332
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Re: More questions!

Postby norm8332 » Thu Jan 25, 2018 8:20 am

Floopy wrote:#1: is the VIC-20s clock a 555 timer, I wouldn't think so?


The 555 holds the reset line low for a period of time upon power up for voltages to stabilize.

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FriedOrange79
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Re: More questions!

Postby FriedOrange79 » Thu Jan 25, 2018 10:35 am

Floopy wrote:#3: how many VICs where sold?


I don't know, but I do know that it was the first computer ever to sell 1 million units.

Floopy wrote:#4: What is the speed of the tape drive? (Ex: 200 Bits per second)


I think it's roughly 300 baud (bits per second). This slowness contributed to the high reliability of Commodore's Datasette relative to other computers' tape systems which were often 2, 4 or 8 times as fast (non-standard fastloaders being even faster but more error-prone, of course).

Floopy wrote: #6: What are the main uses computers had in the 80s


Orion's answer is spot on with regards to home computers like our Friendly Computer, but it's worth noting that in those days there was a sharp division between personal computers designed for home, business or industrial/scientific applications.

Examples of the more 'professional' breeds include the many CP/M machines and IBM compatibles. The HP 85 and similar machines were more like a kind of instrument, often used in laboratories and factories. Some computers of course straddled these lines, such as the early ones from the late 70s and Commodore's own C128 (which, inexplicably, had CP/M capabilities in the mid-80s). Nowadays, personal computers have virtually no differences in their packaging or internal architecture (even the old Mac vs. 'PC' distinction is now limited to their operating systems).

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Floopy
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Re: More questions!

Postby Floopy » Thu Jan 25, 2018 10:40 am

norm8332 wrote:The 555 holds the reset line low for a period of time upon power up for voltages to stabilize.


I figured that it wasn't the clock, it was just a wild guess.
Then where is the 1Mhz clock?

Thanks for the responses, it helps me a lot. I don't know how well high school students will appreciate it, but I will.
It's always fun talking to other people about my passions for obsolescence.
-Floopy

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FriedOrange79
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Re: More questions!

Postby FriedOrange79 » Thu Jan 25, 2018 10:55 am

Floopy wrote:Then where is the 1Mhz clock?.


srowe's link gives the answer: NTSC machines have a 14.31818 MHz crystal oscillator, which gets divided by 14 to produce the 1.022727 MHz clock while on PAL machines it's a 17.734475 MHz crystal divided by 16 to give a 1.108404 MHz clock. These odd frequencies are required for the colour burst signals of the respective analogue colour systems.

The crystal is the silver package visible near the purple VIC chip in your photo.

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Floopy
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Re: More questions!

Postby Floopy » Thu Jan 25, 2018 2:04 pm

FriedOrange79 wrote:
srowe's link gives the answer: NTSC machines have a 14.31818 MHz crystal oscillator, which gets divided by 14 to produce the 1.022727 MHz clock while on PAL machines it's a 17.734475 MHz crystal divided by 16 to give a 1.108404 MHz clock. These odd frequencies are required for the colour burst signals of the respective analogue colour systems.

The crystal is the silver package visible near the purple VIC chip in your photo.

:oops: :oops: :oops:
Thanks I didn't realize it. I was wondering why it was set at 1.023Mhz and not just 1Mhz short, makes sense.
Forgot to mention that everything is NTSC where I'm at, but you probably figured that out.

Like your picture FO.
-Floopy

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FriedOrange79
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Re: More questions!

Postby FriedOrange79 » Thu Jan 25, 2018 10:31 pm

No problem at all.
I'm currently studying to be a high school teacher myself, I look forward to getting started in a couple of years!
And thanks :D

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Re: More questions!

Postby eslapion » Fri Jan 26, 2018 6:22 am

Floopy wrote:A few questions:
#1: is the VIC-20s clock a 555 timer, I wouldn't think so?
#2: the C64 and the VIC-20 both run at 1.023Mhz?
#3: how many VICs where sold?
#4: What is the speed of the tape drive? (Ex: 200 Bits per second)
#5: What is the difference between memory oriented architecture and register oriented architecture in CPUs.
#6: What are the main uses computers had in the 80s

Thank you.

There are a few people who already provided answers to most of these but none who tried to answer them all. My answers may be redundant.

#1: The VIC-20's main clock is the crystal attached to the 6560/6561 VIC-I IC. The NTSC crystal is 14.31818MHz while the PAL crystal is 17.7344MHz. This clock is divided by 14 on the 6560 while it is divided by 16 by the 6561 before being fed to the 6502. The 555 is used to generate the reset pulse at the powering up of the computer, the C64 uses the 556 (a double 555) to also make sure the restore key is pleasant to use.

#2: For NTSC computers, yes. For PAL computers, no. The PAL C64 uses a 17.7344MHz crystal but the 6569 divides this clock by 18 before sending it to the 6510 making the PAL VIC-20 the fastest and the PAL C64 the slowest. Also, on the C64, CPU cycles are stolen by the video chip during screen refresh, more exactly 1000 cycles per refresh or 60'000 cycles per second on the NTSC C64 and 50'000 cycles per second on the PAL C64. This is why the screen goes blank on a C64 when loading/saving to/from the datasette.

#3: According to Wikipedia 2.5 million units.

#4: The datasette's normal loading speed loads up 16kBytes of data in 5 minutes or 300 seconds on a VIC-20/C64 with NTSC architecture but the datasette's normal protocol requires loading/saving the same information twice to detect errors. This is much slower and less efficient than using checksums. This effectively means a VIC-20/C64 with NTSC architecture really loads and saves 32kBytes of data in 300 seconds or 262144 bits. Approximately 900 bits per second. Since the user really only gets half that much data because of the inefficient checking method, it 'feels' like 450 bits per second.

#5: Never heard of that before even in my university courses about CPUs and uCUs.

#6: That's a trick question. The VIC-20 and C64 were considered to be MICROcomputers and were mostly used for games but they were also used to do small business stuff like accounting and word processing. Rich people began using Macintosh and Amiga computers to do more sophisticated stuff like desktop publishing and video editing in the mid/late 1980s. I began using an Amiga in 1989 to publish a small newspaper. Real 'computers' that were the size of refrigerators (or more) and cost the price of a new house (or more) were only used by large businesses, universities and governments mostly for large scale accounting and statistics. The first real processing power users were the military and meteorological experts.

The 1980s saw the advent of 3 different 'classes' of computers. While Commodore computers mostly sold 'home' computers, businesses and the government began offering access to 'personal computers' to more and more employees. Initially equipped only with floppy disk drives, PCs were gradually equipped with access to networks and hard disk drives of ever larger capacities. Very large organisations remained the sole users of business computers or just 'computers' that were very large expensive machines. The Digital VAX-11 was a 'computer' mostly used by businesses in the early 80s.

https://en.wikipedia.org/wiki/VAX-11
No one can do everything. Everyone can do something.

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Floopy
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Re: More questions!

Postby Floopy » Mon Jan 29, 2018 6:39 pm

eslapion wrote:
#5: What is the difference between memory oriented architecture and register oriented architecture in CPUs.

OoPs... :?

I never saw that you replied. Here is my late response.

This page comes from the 6502 software design book.
Untitled.png
-Floopy

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Floopy
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Re: More questions!

Postby Floopy » Mon Jan 29, 2018 6:40 pm

Read the second paragraph.
-Floopy

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FriedOrange79
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Re: More questions!

Postby FriedOrange79 » Tue Jan 30, 2018 1:43 am

It sounds like the textbook author could have invented those terms. I'd suggest that it's basically a shorthand way of saying the 8080 has more registers and the instruction set is geared more towards doing operations on the registers; while the 6800 has only two accumulators and one index register, so the programmer must rely upon the memory more. The 'register-oriented' versus 'memory-oriented' distinction isn't really a dichotomy (such as von Neumann versus Harvard architecture), just a way of boiling down the differences between those two CPUs.

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Re: More questions!

Postby mrr19121970 » Tue Jan 30, 2018 1:58 am

Floopy wrote:This page comes from the 6502 software design book.


I have this book. Great before bedtime reading, no matter how awake you are it will make you pass out after 2 lines.


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