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"Candy" prototype

8-Bit 400 800 cartridge prototype 2600

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#26 ACML OFFLINE  

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Posted Sat Sep 30, 2017 2:02 PM

attachicon.gifIMG_3615.JPG

 

ClausB here is a HDR picture of the motherboard. Sorry but I'm not the best photographer.  I can try to take better pictures at a point where I have some more time. 

Wow!  Looks like it has hand soldered.  Very nice piece of Atari history.   



#27 ClausB OFFLINE  

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Posted Sun Oct 1, 2017 7:24 AM

Also interesting is there are only 2 ROM sockets, so this was designed before the need for the Math ROM. Shame the 2 OS ROMs aren't there.

The LSTTL chips at left are not the same as in production 400s. There is no LS42 for decoding the address space into 8K blocks. Rather the single LS138 decodes it into 4K blocks, but only 8 of them. My early 800 has 2 LS138s for 16 4K blocks. This incomplete decoding in the early 400 is diagrammed on page 73 of DeCuir's 1978 notebook. It limits this 400 to at most 12K of RAM.

#28 slx OFFLINE  

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Posted Sun Oct 1, 2017 7:55 AM

 This incomplete decoding in the early 400 is diagrammed on page 73 of DeCuir's 1978 notebook. It limits this 400 to at most 12K of RAM.

 

The level of detail of some people's knowledge never ceases to amaze! 

 

Good decision by Atari to upgrade this to allow at least 48K of RAM.



#29 JamesD OFFLINE  

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Posted Sun Oct 1, 2017 11:03 AM

12K is little more than a game console would need.



#30 ClausB OFFLINE  

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Posted Sun Oct 1, 2017 7:37 PM

Page 73 of Decuir's 1978 notebook (https://archive.org/...ingNotebook1978) shows the memory map resulting from the incomplete decoding. Each 4K block is mirrored twice within the 6502's 64K address space:

jd73.png

 

Page 88 shows the actual decoding circuit. Notice A15 is missing. This technique saves a chip:

jd88.png


Edited by ClausB, Sun Oct 1, 2017 7:40 PM.


#31 JamesD OFFLINE  

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Posted Sun Oct 1, 2017 8:10 PM

It makes you wonder if they were designing it as more of a game console, or introductory computer.
 



#32 ClausB OFFLINE  

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Posted Mon Oct 2, 2017 5:08 PM

Flip through that notebook. Lots of notes, not only technical, but also meeting results, questions and decisions. Even focus group results, showing little interest in pure gaming.

#33 jacobus OFFLINE  

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Posted Wed Oct 4, 2017 4:39 AM

Thanks very much for sharing, that is an amazing bit of history!

 

 

I had to laugh at Curt's initial reaction of "Mine!  Gimme!"   Priceless!



#34 Tempest OFFLINE  

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Posted Wed Oct 4, 2017 7:21 AM

I had to laugh at Curt's initial reaction of "Mine!  Gimme!"   Priceless!

Well there was a good reason for that.  Interesting that there are two 'one of a kind' prototypes now though.



#35 mytekcontrols OFFLINE  

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Posted Wed Oct 4, 2017 8:48 AM

I had to laugh at Curt's initial reaction of "Mine!  Gimme!"   Priceless!


I also got a kick out of that as well. So now we know that Curt still watches these forum's, even though he rarely makes his presence known. And that all we have to do to get him to reveal himself is dangle a piece of something he once had possession of.

- Michael

#36 atarikid1968 OFFLINE  

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Posted Wed Oct 4, 2017 5:05 PM

Tempest, there isn't "two" one of a kind prototypes for the 400.  What Curt was talking about is that Doug also had the first "Stella" (2600 of course) in his possession.  He had the 2600 and 400 but unfortunately Doug believed in a video store owner and let him borrow it as a display and never received it back.  I'm currently trying to track down the store owner to see if I can retrieve it.  I'm so blown away with the knowledge and passion of everyone on here and I'm just disappointed that I didn't know about this before Doug passed away; he would have loved this site.  I'd still like to upload some of Doug's audio recordings talking about how and why they designed things the way they did.  Plus his description of how things were done at Atari is just the best.  



#37 Stephen OFFLINE  

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Posted Wed Oct 4, 2017 5:21 PM

Tempest, there isn't "two" one of a kind prototypes for the 400.  What Curt was talking about is that Doug also had the first "Stella" (2600 of course) in his possession.  He had the 2600 and 400 but unfortunately Doug believed in a video store owner and let him borrow it as a display and never received it back.  I'm currently trying to track down the store owner to see if I can retrieve it.  I'm so blown away with the knowledge and passion of everyone on here and I'm just disappointed that I didn't know about this before Doug passed away; he would have loved this site.  I'd still like to upload some of Doug's audio recordings talking about how and why they designed things the way they did.  Plus his description of how things were done at Atari is just the best.  

Please do so - this information is absolutely priceless.



#38 Bryan OFFLINE  

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Posted Wed Oct 4, 2017 6:50 PM

I'm so blown away with the knowledge and passion of everyone on here and I'm just disappointed that I didn't know about this before Doug passed away; he would have loved this site.

We would have loved it if he had been on here. Today there's a million similar technology products in development at any one time, but back in the '70s there were so many instances where things were being done for the first time by a very small team who had no real road map of how to get there. I'd love to hear Doug's stories.



#39 ClausB OFFLINE  

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Posted Wed Oct 4, 2017 6:59 PM

This preproduction cart would fit in this 400:
http://atariage.com/...s/#entry2606542

#40 Tempest OFFLINE  

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Posted Wed Oct 4, 2017 8:16 PM

Tempest, there isn't "two" one of a kind prototypes for the 400.  What Curt was talking about is that Doug also had the first "Stella" (2600 of course) in his possession.  He had the 2600 and 400 but unfortunately Doug believed in a video store owner and let him borrow it as a display and never received it back.  I'm currently trying to track down the store owner to see if I can retrieve it.  I'm so blown away with the knowledge and passion of everyone on here and I'm just disappointed that I didn't know about this before Doug passed away; he would have loved this site.  I'd still like to upload some of Doug's audio recordings talking about how and why they designed things the way they did.  Plus his description of how things were done at Atari is just the best.  

Gotcha. I misread that.

#41 MrFish OFFLINE  

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Posted Thu Oct 5, 2017 7:17 AM

This preproduction cart would fit in this 400:
http://atariage.com/...s/#entry2606542

 

Interesting... I missed that thread at the time.



#42 Heaven/TQA OFFLINE  

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Posted Thu Oct 5, 2017 7:47 AM

cool pics... interesting how far we got into designs of motherboards... look how "big" and much space between the parts are... that's why I love my 800 model.



#43 JamesD OFFLINE  

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Posted Thu Oct 5, 2017 9:34 AM

Do you think the 2nd cart on the 800 was partially because the first cart didn't have enough address lines to do a lot?
No I haven't read the contents of the notebook yet, I'm low on data until next week.



#44 Bryan OFFLINE  

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Posted Thu Oct 5, 2017 9:42 AM

Do you think the 2nd cart on the 800 was partially because the first cart didn't have enough address lines to do a lot?
No I haven't read the contents of the notebook yet, I'm low on data until next week.

That may have been part of the thinking, but the stated reason was that they wanted a system of program cartridges that would be combined with various data cartridges to make an expandable system.



#45 Rybags ONLINE  

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Posted Thu Oct 5, 2017 9:49 AM

Without having read the notebook, I would suspect:

. they were probably just concerned in the early days with having a working system to test OS, languages, applications and games and the minimalist configuration compared to what we have probably was never intended to be the production config.

 

. 800, the modular strategy probably foresaw teamed up language and utility/Dos carts in left/right slots which never really eventuated and was independent and irrespective of the early low capability slot.

 

Maybe a little strange that nobody ever bothered doing a Dos on Right Cartridge though it would have meant an 8K Ram hole.  Though doing it as switchable with a bit of low-Ram resident code could have utilized the $8000-$9FFF Ram as buffers.

Probably questionable value though, having a Dos that left you with around 29K low Ram and 8K high Ram if the left cart wasn't present.



#46 JamesD OFFLINE  

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Posted Thu Oct 5, 2017 11:01 AM

Without having read the notebook, I would suspect:
. they were probably just concerned in the early days with having a working system to test OS, languages, applications and games and the minimalist configuration compared to what we have probably was never intended to be the production config.

That I would believe.  The size may have been as simple as "how much space to you think we'll need for BASIC?"
 

. 800, the modular strategy probably foresaw teamed up language and utility/Dos carts in left/right slots which never really eventuated and was independent and irrespective of the early low capability slot.

I was kinda thinking a standard BASIC and an Extended BASIC upgrade.  That's sort of the route Microsoft was taking.  
But that would leave questions around the 400.
 

Maybe a little strange that nobody ever bothered doing a Dos on Right Cartridge though it would have meant an 8K Ram hole.  Though doing it as switchable with a bit of low-Ram resident code could have utilized the $8000-$9FFF Ram as buffers.
Probably questionable value though, having a Dos that left you with around 29K low Ram and 8K high Ram if the left cart wasn't present.

The one major oversight in the design of these machines, was not foreseeing banking out ROM for RAM.
Anything that would bring the Atari closer to that would help, but without support beyond the 800, I question the usefulness.
The Apple language card didn't come out until 1979, so I don't see how Atari could have foreseen that.
 



#47 Bryan OFFLINE  

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Posted Thu Oct 5, 2017 11:16 AM

The one major oversight in the design of these machines, was not foreseeing banking out ROM for RAM.

There was a time when 64K was considered vast. So vast, in fact, that saving a few cents on logic ICs was preferable to decoding the address space efficiently. They probably also thought that these computers would be replaced with something new in a few years anyway.

 

In the end, Atari did improve the 400 and 800 specs over the development cycle, and the 800's 48K limit is pretty reasonable considering that it would have been a lavish system for the home in 1979.



#48 JamesD OFFLINE  

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Posted Thu Oct 5, 2017 5:08 PM

There was a time when 64K was considered vast. So vast, in fact, that saving a few cents on logic ICs was preferable to decoding the address space efficiently. They probably also thought that these computers would be replaced with something new in a few years anyway.

 

In the end, Atari did improve the 400 and 800 specs over the development cycle, and the 800's 48K limit is pretty reasonable considering that it would have been a lavish system for the home in 1979.

Yeah, 64K was vast at the time since assembly language or BASIC were the norm at the time, and it wasn't even an Extended BASIC.
Star Trek was a large BASIC program, and most machines used printable graphics (semi-graphics).
I think hi-res graphics were a major contributor to the drive for more RAM.
 



#49 ClausB OFFLINE  

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Posted Thu Oct 5, 2017 5:24 PM

Look at DeCuir's memory map (and my 800 #26 thread) and see they had planned only 36K RAM for the 800, with no overlap with cart ROM. I think DOS in the right cart would have made sense with a language in the left cart. Free RAM would have been a little more even than in a production 800 with BASIC cart and DOS loaded from disk.
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#50 DrVenkman OFFLINE  

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Posted Thu Oct 5, 2017 6:04 PM

64K RAM wasn't just vast for the era, it was EXPENSIVE! People today don't realize quite how expensive. Memory prices were so exorbitant, and the market so cut-throat even into the 80's, that Jack's Atari Corp. was investigated by the FBI for illegal DRAM chip imports. 

 

atariage.com/forums/topic/207245-secret-atari-dram-resale-operation-revealed-by-fbi/

 

The link in the first post is dead, but Kevin Savetz has reposted the FOIA response from the FBI at Archive.org:

 

www.atariarchives.org/atarileaks/

 

I have no doubt that the relative cost of DRAM was a major impact in those initial designs.







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