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1088XEL Alternative Mother-Board Project

Alernative Motherboard Redesign New Advanced Atari 8-bit

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#826 mytekcontrols OFFLINE  

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Posted Sat Aug 12, 2017 10:25 AM

Status and Other Stuff

  • PAL tests on Stephens board still looking good, so apparently there might have been an issue with his PSU that was affecting overall stability since that is the only thing that changed. The remnant of PMG issues also went away when I switched the 74LS08 to a 74F08, which is associated with both PH0 and PH2 buffering.
  • For the main crystal (PAL or NTSC) to be interchangeable, there is a socket formed from a fragment of a Machine Pin IC socket. This has not been reliable, and tightness varies between different manufacturers. The problem relates to the smaller lead diameter and different lead shape of the crystal vs an actual IC. So I have been investigating an alternative made by TE Connectivity, but I don't really like the cost at $0.73 for each pin (it'll take two of them). So if someone could suggest a viable alternative or a cheaper source that would be great. Also looked at crystal sockets suitable for a HC49U series crystal, but the choice appears to be limited and also expensive.

2-5332095-4.JPG
ART-MINI%20SPRING%20SOCK-CLOSED.jpg
Digi-Key P/N: A32369-ND (Manufacture P/N 2-5332095-4) Note: more specific specifications are available in this datasheet.

 

- Michael


Edited by mytekcontrols, Sat Aug 12, 2017 10:29 AM.


#827 Bryan OFFLINE  

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Posted Sat Aug 12, 2017 10:33 AM

  • For the main crystal (PAL or NTSC) to be interchangeable, there is a socket formed from a fragment of a Machine Pin IC socket. This has not been reliable, and tightness varies between different manufacturers. The problem relates to the smaller lead diameter and different lead shape of the crystal vs an actual IC. So I have been investigating an alternative made by TE Connectivity, but I don't really like the cost at $0.73 for each pin (it'll take two of them). So if someone could suggest a viable alternative or a cheaper source that would be great. Also looked at crystal sockets suitable for a HC49U series crystal, but the choice appears to be limited and also expensive.

 

1. Dual-wipe sockets hold undersized stuff better unless the spring tension has been ruined by shoving fat pins in there, but you could also solder the crystals to a DIP component header. These can frequently be found through surplus houses for cheap.

 

http://www.jameco.co...word=dip-header

 

2. You could ditch the crystals in favor of oscillators designed to fit into sockets (xtal and driver in a single package). This eliminates the crystal buffer circuitry (R35, R36, R37, R38, R39, R40, Q7, Q8) and could replace the X2 circuit as well. A switchable dual oscillator PCB module could then be made for this socket.

 

There are companies who make dual programmable oscillators, so you could have any 2 switchable frequencies in a single package, but you have to buy the programmer.

 

http://www.cardinalx...le-oscillator-3

crystal_oscillator_ic_s.jpg



#828 Van OFFLINE  

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Posted Sat Aug 12, 2017 11:08 AM

You might consider a three position screw terminal like this https://www.sparkfun.../products/10571The 2.54mm ones should match the existing footprint, the down side is they aren't too robust and the screws can be over tightened/opened and strip.

 

Other option could be soldering xtal leads to a cut down component carrier, https://www.digikey....10/A101-ND/4258They are a little spendy, but one could be cut to prep both xtals.

Yogi



#829 remowilliams OFFLINE  

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Posted Sat Aug 12, 2017 11:15 AM

There are companies who make dual programmable oscillators, so you could have any 2 switchable frequencies in a single package

 

Ooh, I like the sound of that..



#830 mytekcontrols OFFLINE  

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Posted Sat Aug 12, 2017 11:43 AM

 

1. Dual-wipe sockets hold undersized stuff better unless the spring tension has been ruined by shoving fat pins in there, but you could also solder the crystals to a DIP component header. These can frequently be found through surplus houses for cheap.

 

http://www.jameco.co...word=dip-header

 

2. You could ditch the crystals in favor of oscillators designed to fit into sockets (xtal and driver in a single package). This eliminates the crystal buffer circuitry (R35, R36, R37, R38, R39, R40, Q7, Q8) and could replace the X2 circuit as well. A switchable dual oscillator PCB module could then be made for this socket.

 

There are companies who make dual programmable oscillators, so you could have any 2 switchable frequencies in a single package, but you have to buy the programmer.

 

http://www.cardinalx...le-oscillator-3

crystal_oscillator_ic_s.jpg

 

The X2 circuit is phase locked into the X1 circuit's output, so I think I would prefer to leave that as is, since the total cost of parts is relatively cheap and readily available (and it works fine, so at this stage I don't want to introduce any new potential problems). As for using oscillators... that was my original intention, and was seen in the early designs, but then I hit a snag with getting one with the non-standard PAL frequency (3.546894 Mhz). Although no problem with getting one in the standard NTSC colorburst frequency. So in an effort to keep this more or less off the shelf, I went in favor of the crystals, which can be gotten for $1 or less. Bottom line, I'm not looking at making anymore changes to the circuits, and although a cool idea with using a programmable and/or dual frequency oscillator, that is a big departure from what I have going at the present time. Custom spec'ed oscillators are also out of the question when we are talking about buying only one or two of something keeping in mind that this is a DIY board.

 

And lets face it, it's not like you are going to be able to change the system from PAL to NTSC with the flip of a switch anyway, unless you also have two Antic's and two GTIA's on board. So the convenience of a switched dual frequency oscillator really loses it's advantage when you factor in having to also pop out two 40 pin chips and pop in two new ones to take their place each and every time. Most likely a user will stick to one mode (either PAL or NTSC) on any given XEL, because it sure would be a pain switching chips all the time  ;) . I plan on having one XEL as PAL, and another XEL setup as NTSC.

 

However I do like the idea of using a fragment of a DIP dual leaf socket instead, so I'll have to check that out  :) .

 

- Michael



#831 Bryan OFFLINE  

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Posted Sat Aug 12, 2017 11:53 AM

Okay, you're right then that oscillators wouldn't work easily for X2. You could probably find multiples of the PAL frequency more easily than 3.54..



#832 mytekcontrols OFFLINE  

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Posted Sat Aug 12, 2017 1:57 PM

Okay, you're right then that oscillators wouldn't work easily for X2. You could probably find multiples of the PAL frequency more easily than 3.54..

 

Bryan I do appreciate all of the ideas, but at this point the design is pretty much what it is, and I'm just zeroing in on components and sourcing as I clean up the BOM. No plans to change things with the circuitry... I think its time to lock this down and get on with other aspects  :) .

 

I now have a fully working system in V1.1  :thumbsup:

 

- Michael



#833 Bryan OFFLINE  

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Posted Sat Aug 12, 2017 2:56 PM

Bryan I do appreciate all of the ideas, but at this point the design is pretty much what it is, and I'm just zeroing in on components and sourcing as I clean up the BOM.

 

I totally understand. Just throwing things out there.



#834 orpheuswaking OFFLINE  

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Posted Sat Aug 12, 2017 3:18 PM

I was going to suggest spots for both crystals and a jumper between the two. But then we get back to changing the existing board. 



#835 mytekcontrols OFFLINE  

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Posted Sat Aug 12, 2017 3:32 PM

I was going to suggest spots for both crystals and a jumper between the two. But then we get back to changing the existing board.


Not only that, but we are running out of room in that area of the board so it would require shoving stuff around to make room. If the dual leaf socket idea works (thanks Bryan), that should solve it and not require any board changes. I'll be testing that out real soon.

- Michael

#836 seastalker OFFLINE  

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Posted Sun Aug 13, 2017 7:52 AM

Since the board is really getting close to being ready, when the designs are released, I thought I'd take the temperature on any interest in drop in xl replacement boards. I also ask if anyone knows of the latest news of skilled individuals who plan to create one?  I'd love to see it happen.  Huge bonus would be if one board fit the 600, 800, and others. Dual Pokey would be amazing as would a NTSC/PAL switch with a GTIA/ANTIC cartridge (hey, I can dream...)   



#837 Dropcheck OFFLINE  

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Posted Sun Aug 13, 2017 11:03 AM

Since the board is really getting close to being ready, when the designs are released, I thought I'd take the temperature on any interest in drop in xl replacement boards. I also ask if anyone knows of the latest news of skilled individuals who plan to create one?  I'd love to see it happen.  Huge bonus would be if one board fit the 600, 800, and others. Dual Pokey would be amazing as would a NTSC/PAL switch with a GTIA/ANTIC cartridge (hey, I can dream...)   

 

Huh?



#838 mytekcontrols OFFLINE  

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Posted Sun Aug 13, 2017 11:21 AM

Since the board is really getting close to being ready, when the designs are released, I thought I'd take the temperature on any interest in drop in xl replacement boards. I also ask if anyone knows of the latest news of skilled individuals who plan to create one?  I'd love to see it happen.  Huge bonus would be if one board fit the 600, 800, and others. Dual Pokey would be amazing as would a NTSC/PAL switch with a GTIA/ANTIC cartridge (hey, I can dream...)


Ditto on the Huh?

If I'm understanding this correctly, I think a new topic would be more appropriate, since it sounds like you are looking at an entirely different board project and a different creator of such.

- Michael

#839 seastalker OFFLINE  

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Posted Mon Aug 14, 2017 8:34 AM

Sorry if I wasn't clear. Is anyone actively planning to adjust Michael's design plans to clone one that fits any original XL cases? Looking at the new C64 Reloaded board inspired stereo Pokey and fast region switching. Rather than adjusting the board's finalized functionality, I was dreaming out loud of a cartridge solution or other expansion.  I may sound a little "out there" at times. :)



#840 Dropcheck OFFLINE  

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Posted Mon Aug 14, 2017 9:45 AM

Sorry if I wasn't clear. Is anyone actively planning to adjust Michael's design plans to clone one that fits any original XL cases? Looking at the new C64 Reloaded board inspired stereo Pokey and fast region switching. Rather than adjusting the board's finalized functionality, I was dreaming out loud of a cartridge solution or other expansion.  I may sound a little "out there" at times. :)

 

Not any realistic possibility.  Michael's video and audio and keyboard output/input options would not be a dropin fit.  You would have to modify the case rear rather extensively.  Add to that the cost of the four layer board at the size of the 600/800 case would make it extremely expensive just for the bare board.  Particularly at the small hobby run numbers. 

 

There are upgrade options for the original 600/800XLs.  Some of them do not require much if any case mods.  Some of them are even solderless upgrades. 



#841 mytekcontrols OFFLINE  

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Posted Mon Aug 14, 2017 10:09 AM

Sorry if I wasn't clear. Is anyone actively planning to adjust Michael's design plans to clone one that fits any original XL cases? Looking at the new C64 Reloaded board inspired stereo Pokey and fast region switching. Rather than adjusting the board's finalized functionality, I was dreaming out loud of a cartridge solution or other expansion.  I may sound a little "out there" at times. :)

 

I did understand the aspect of making a version that fits into an existing A8 case, but was a bit confused about the suggested cartridge solution (with that last part still being a bit unclear). However since this project fairly quickly evolved into creating a Mini-ITX A8 Alternative Motherboard, I would still recommend starting a 'new' topic if you wish to explore the possibilities that you are suggesting, just so that this one doesn't get taken too much off track.

 

BTW, "out there" is perfectly good, and is behind projects such as the 1088XEL  :) .

 

- Michael



#842 Kyle22 OFFLINE  

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Posted Mon Aug 14, 2017 11:53 AM

I thought he meant having ANTIC, GTIA, and the crystals on a removable module to facilitate easy PAL/NTSC switching.



#843 mytekcontrols OFFLINE  

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Posted Mon Aug 14, 2017 12:17 PM

I thought he meant having ANTIC, GTIA, and the crystals on a removable module to facilitate easy PAL/NTSC switching.

 

I get it now, and that does make better sense  :) . However that would require at least one additional board to create a plug-in module (two extra boards in order to make it swappable). And assuming you wish to do that whenever the mood strikes, a way would need to be provided to swap 'modules' from the outside of the case. Sounds like a lot of extra expense, and not something I'll likely implement on this project.

 

- Michael



#844 mytekcontrols OFFLINE  

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Posted Mon Aug 14, 2017 1:18 PM

Update: Status of PAL Related Problems

 

With Stephen's board sporting the 74F08 chip I've seen no PAL issues thus far, or at least none associated with PAL demos or games. However I did find one demo that works fine under NTSC, but has a problem in PAL mode, at least on the 1088XEL. This demo produces the same result on all 3 XEL's I have over here when configured for PAL video.

 

ZtSnyYW.jpg

 

This file shows the problem pictured above: Attached File  Super Boink (19xx)(Bob Armour).atr   90.02KB   9 downloads

 

And this one works just fine: Attached File  Atari 8-bit Boink.xex   9.48KB   8 downloads

 

Can someone with a real PAL A8 test the ATR version and let me know if you see the same thing as I am?

 

Thanks  :)

 

- Michael

 



#845 Stephen OFFLINE  

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Posted Mon Aug 14, 2017 2:36 PM

Crap - I don't have a working PAL machine.  Still haven't ordered a working flash chip for my 2nd U1MB.  Hope the issue is with the demo :)



#846 foft OFFLINE  

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Posted Mon Aug 14, 2017 2:53 PM

I don't see it on my 600XL with 1064



#847 mytekcontrols OFFLINE  

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Posted Mon Aug 14, 2017 4:13 PM

Crap - I don't have a working PAL machine.  Still haven't ordered a working flash chip for my 2nd U1MB.  Hope the issue is with the demo :)

 

Well I wouldn't go as far as to say that. Thus far this is the one and only program that shows this aberration out of dozens I've tested. interesting that it's not 'specifically' a PAL demo, and also interesting that the other one that I got from fandal's site runs just fine.

 

Interesting thing is that I've tried substituting the following chips for the 74F08 without any affect: 74ABT08, 74ACT08 both of which are even faster than the F08.

 

Might be interesting to see what the ATR version of Super Boink is doing with the PMG aspect, and then duplicate that in a basic program to see if the problem is still present. this is merely a suggestion, because I don't know enough (or maybe better to say... remember enough) to be able to do something like that.

 

 

I don't see it on my 600XL with 1064

 

Thanks for the confirmation  :) .

 

- Michael



#848 Theoryman OFFLINE  

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Posted Mon Aug 14, 2017 4:29 PM

That is good news!

 

So, no more changes needed?

 

--



#849 mytekcontrols OFFLINE  

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Posted Mon Aug 14, 2017 4:30 PM

Problem resolved  :thumbsup:  Had to deactivate Basic prior to loading ATR.

 

I guess the XEX version automatically does that. Interesting that the only thing that gets borked with Basic enabled, is that little bit of PMG stuff.

 

- Michael



#850 mytekcontrols OFFLINE  

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Posted Mon Aug 14, 2017 4:31 PM

That is good news!

 

So, no more changes needed?

 

--

 

Doesn't appear to need any  :)

 

- Michael







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