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Interest in a 4MB Axlon Compatible SRAM Card for the Atari 800


reifsnyderb
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Hello,

 

@Faicuai asked me if it's possible to build a 4MB (+48k base memory) Axlon Compatible SRAM Card for the Atari 800.  It's possible.  I haven't done so because I estimate that to build one in small quantities will result in a card that is at least $125.  This is mainly due to assembly, troubleshooting, and testing time.  (Troubleshooting because it's not uncommon when assembling a board by hand to have to track down a bad solder connection...and this can take a while.)  Also, the 1MB SRAM chips are around $8 each.  If I can't keep the board to within 100mm in size, the board price will go up yet another $7, or so, each.  If there's enough interest, I'll design one and get them made.  It will probably take a couple days just to design one, too.

 

So, if there's enough interest, I'll get on it.

 

Brian

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Guess it comes down to the need for 4mb. I am quite happy with 1MB in the Incognito on the 800, and for the 1MB in U1MB for Ramdisk, demos, (Rewind. alley dog), 1MB games and loading multi ATR games like Brundles all into memory, but not sure I'd need 4mb. No to dissuade you as there may well be interest. (If the Geos O/S port takes off for example I can see it being utilised)

 

There is Antonia 4mb plugin upgrade for XL/XEs afterall, so maybe 4mb for the 800 is a good thing.

 

 

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11 minutes ago, Vyvyan B. said:

Would it be possible to make it modular, with socketed sram so you could start with 1mb or 2mb and upgrade as needed?

The 1MB chips are surface mount, so it wouldn't be feasible.  Sorry.  The 512k chips do come in DIP packages and could be socketed...but they'd take up a lot of space and would take 8 chips to make it happen.

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9 minutes ago, Vyvyan B. said:

Since they are SMD, adding them in at a later date wouldn't take much doing with a mediocrum of soldering skills. Could you not simply leave them out to create 1,2 and 4mb versions?

That is a possibility, yes.  It could be done.  The package is a TSOP-II so the pins have 0.8mm centers.  I'd say that somebody skilled with a soldering iron could do it or somebody with a hot-air soldering station and some experience could pull it off.  Many times I'll touch up the pins with a soldering iron.

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This is WONDERFUL!

 

A 4MB AXLON-compatible ram upgrade for the 800 is like anything out there, except Antonia, on 800XL (!)

 

Now that we are at it, let's give it a shot at being the bad-ass, mother-of-all RAM upgrades for many stock 800 users out-there:

 

  1. Full support of AXLON ($4000-$7FFF) and MOSAIC ($C000-$CFFF) banking-schemes and HW registers (Ok. if optional line is required to O/S board for MOSAIC).
  2. Up to 4MB or RAM, with logic to simultaneously support multiple arrangements:
    • 4MB dedicated to AXLON ram.
    • 3MB dedicated to AXLON ram, and up to 1MB dedicated to MOSAIC ram.
    • 4MB dedicated to AXLON ram and up to 1MB dedicated to MOSAIC provisioned on-board multi-OS personality board (?)
  3. Slot-3 (last one, on the back) remains completely free and fully operational under any arrangement, in order to support Bit3, Franklin-Austin, and any other future re-creation or innovation designed for this special slot on the 800.
  4. Fully compatible with SIDE 1/2/3, SDX, and both LEFT and RIGHT carts (!!)
  5. As power efficient as components allow for target price range.
  6. On-board RAM battery-backup for those users who only have SIO-storage and wish to preserve their RAM-based DOS drives 24x7, for as long as battery remains operational (cleverly located away from key components for protection against leakage, and easily accessible at the TOP-edge of the board, for live / hot replacement if failing).

 

These are only some ideas, based on actual experience with the 800 and its unique (and kind-of-open) architecture. An upgrade like this will also have tremendous historical value, as it will capture the expansion concepts and innovations available on the 800 LONG before anything in the A8 lineup, and will also be welcome by "royal-pain-in-the-ass" collectors like me (and others here), who will always prefer well engineered, drop-in, fully reversible upgrades.

 

Will happily install this on my 040-0077 A800, and preventively retire some of its original RAM/ROM components.

 

Bring it on!

Edited by Faicuai
(Structure, clean-up, syntax)
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@Faicuai:  Mosaic and Axlon are pretty much mutually exclusive.  This is because of Axlon's use of $CFC0-$CFFF as banking registers.  (They all are the same register, really.)  Mosaic also doesn't have enough registers to support more than about 192k or so.  

 

Check out my RAMROM 2020 board.  It supports Mosaic banking for up to 128k.  Unfortunately, I haven't found much software that uses Mosaic banking.  I did make some of the Newell suggested ROM upgrades and I like those.

 

 

Adding battery backup support to a 4MB card shouldn't be a problem.  My RAMROM 2022 board has it and it works.   🙂  I have no idea how long the battery would last, though.   lol    Maybe it would be a good idea to add leads so an external battery could be added?

 

My thought is to use the RAMROM 2022, 4MB Axlon (with battery back-up), and a Bit 3 card.  All would fit.  

 

I am also doing some testing with a W65C02 chip and it works in a 400.  Since this chip can do up to 14 Mhz, I just made up a board to test out on an XL at speeds up to 7Mhz.  If a turbo mode is possible, it may be able to be squeezed onto my 400/800 CPU card.  No promises on that one, though.

 

 

 

 

 

 

 

 

 

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42 minutes ago, reifsnyderb said:

Mosaic and Axlon are pretty much mutually exclusive.  This is because of Axlon's use of $CFC0-$CFFF as banking registers.  (They all are the same register, really.)  Mosaic also doesn't have enough registers to support more than about 192k or so.  

Yes, of course, you are correct. In fact, I actually wrote a set of memory-test utilities specifically designed for AXLON and MOSAIC, at the time their support was concurrently added to Incognito's JED (thanks to some magic done by Candle, who squeezed out space and code where it seemed not possible!! As a result, Incognito supports BOTH memory models in Colleen mode, plus correct handling of EXTSEL to maintain Slot-3 operational and compatible with Bit3 !!!).

 

However, that does not mean you have to stop there. You can have your board/s respond to MOSAIC HW-register with full range of $00-$FF data on the bus, so you can squeeze out 256*4KB = 1024 KB out of that mode. Just for fun, since most of bus-control will be modeled on soft-logic, anyway. Also, I do not recall finding $CFC0-$CFFE hot on my AXLON board... only $CFFF... I will re-check, even on Incognito.

 

Also, don't worry about past SW for MOSAIC. The name of the game here would be to preserve the historical value of such innovation and make it available to any 800 user. It goes a long way to show how far the 800 architecture could be pushed back in the day, with little effort.

 

42 minutes ago, reifsnyderb said:

Check out my RAMROM 2020 board.  It supports Mosaic banking for up to 128k.

Beautiful! I am all fine with a RAMROM + RAM expansion combo. I will check this board. Is it ready for sale? Where?

 

42 minutes ago, reifsnyderb said:

My thought is to use the RAMROM 2022, 4MB Axlon (with battery back-up), and a Bit 3 card.  All would fit.  

There you have it, a real bad-ass setup on the 800. I have several Bit3 cards to boot, here. Only wish I could keep them plugged but powered from the bus, only when needed, to protect their lifespan. In any case, having Slot-3 free and ready for a drop-in Bit3 on the 800 is music to my ears! 

 

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5 minutes ago, Faicuai said:

However, that does not mean you have to stop there. You can have your board/s respond to MOSAIC HW-register with full range of $00-$FF data on the bus, so you can squeeze out 256*4KB = 1024 KB out of that mode. Just for fun, since most of bus-control will be modeled on soft-logic, anyway. Also, I do not recall finding $CFC0-$CFFE hot on my AXLON board... only $CFFF... I will re-check, even on Incognito.

A modified Mosaic register would work.  Mosaic only responds to writes to the address and not to the data bus.  Having a Mosaic register respond to the data lines is, of course, possible....but incompatible.  

 

The Axlon specification is for $CFC0-$CFFF.  However, it's quite possible that only $CFFF is used in some places.  The original specification would have been to save adding extra chips to the board.  Because of the chip shortage, I've been forced to use 74 series glue logic as opposed to CPLD's.  So, if possible, I don't add the extra chips either.

 

 

5 minutes ago, Faicuai said:

 

Beautiful! I am all fine with a RAMROM + RAM expansion combo. I will check this board. Is it ready for sale? Where?

 

There you have it, a real bad-ass setup on the 800. I have several Bit3 cards to boot, here. Only wish I could keep them plugged but powered from the bus, only when needed, to protect their lifespan. In any case, having Slot-3 free and ready for a drop-in Bit3 on the 800 is music to my ears! 

 

The RAMROM 2022 is ready for sale.  I'll put it up on my website (https://www.5cfab.com) really soon.

 

Software compatibility is a problem.  For example, on an XL the spec. allows for banking at $D1FE.  However, nothing was ever written to use $D1FE for banking.  Also, the spec. is rather limiting for $D1FE banking as they didn't use an Axlon type scheme at that address.  If $D1FE would be used for banking, and all 256 bytes used, an XL could easily have 4MB available on a 1090 expansion system.  Quite frankly, the way the 1090 is designed, an XL could have access to 20MB of RAM...with the right software.

 

 

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41 minutes ago, reifsnyderb said:

The Axlon specification is for $CFC0-$CFFF.  However, it's quite possible that only $CFFF is used in some places.  The original specification would have been to save adding extra chips to the board.  Because of the chip shortage, I've been forced to use 74 series glue logic as opposed to CPLD's.  So, if possible, I don't add the extra chips either.

So I confirmed this: on my Incognito with latest EXTSEL .JED, AXLON banking is "hot" ONLY on $CFFF, whereas on my AXLON-compatible stock 800, $CFC0-$CFFF is, indeed.

 

Stick to $CFFF and get rid of any unnecessary baggage on the board. Altirra OS-b compatible OS is $C000-$CFFF friendly, and we can chop last page via OS ram-vectors, and E: handlers opens just fine right below it, thus giving almost full 4KB of extra RAM in that region.

 

Let it roll !!

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11 minutes ago, Faicuai said:

So I confirmed this: on my Incognito with latest EXTSEL .JED, AXLON banking is "hot" ONLY on $CFFF, whereas on my AXLON-compatible stock 800, $CFC0-$CFFF is, indeed.

 

Stick to $CFFF and get rid of any unnecessary baggage on the board. Altirra OS-b compatible OS is $C000-$CFFF friendly, and we can chop last page via OS ram-vectors, and E: handlers opens just fine right below it, thus giving almost full 4KB of extra RAM in that region.

 

Let it roll !!

 

Another chip and capacitor need added to limit the register to just $CFFF.  A 74__21 and a 100nF capacitor.

 

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1 hour ago, reifsnyderb said:

Ok.  It looks like this board will have to be larger than 100mm on one side.  So, I'll make it a 2 layer board, to keep the "engineering fee" down, and space the chips out to make it easier to lay out.

 

Just came back from dinner-time out, and on gave this a second thought... Just don't call me crazy (although I may be, 😁)

 

What about enhancing AXLON current bus-control logic so (say) specifically writing to $CFFF (per current AXLON implementation) and then immediately followed by a (read or write) of $CFFE (in that order ONLY), will cause a HW-select of next 4MB block.... so we could build a 16MB monster card (!!??)

 

The physical memory layout could be 4x4MB or 8x2MB chips (I do know the latter 2MB chips are used on my Apple II Platinum AE-compatible 4MB Ramworks-IIII expansion from Reactive Micro). The board could be built and populated to a given spec. range (eg. 2MB, 4MB, up to 16MB). Power consumption needs to be checked against what can be supplied from system-board on EDGE connector.

 

Have you thought about going (really) big, here? Imagine the (relatively) large size of that RAM-drive (!!??)

 

 

 

Edited by Faicuai
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3 minutes ago, reifsnyderb said:

@Faicuai:  Something like that is possible, sure.  My concern is that deviating from the Axlon spec. will result in something that won't be able to be used.

It all depends where the second bank-switch register is placed and the specific write/read sequence... That is the key. 4MB-window select could be within AXLON range or, say, on $F000, for instance...

 

It is worth a thought, from an implementation and board-design (density, dimensions, etc.) point of view.

 

A good chance to build something truly memorable for the A400/800... 

Edited by Faicuai
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@Faicuai

 

I am thinking about how the VBXE and Rapidius add a lot to the Atari but I don't think there's much developed that can use those to their full potential.  Making a battery backed up 4 MB Axlon card can be used by a lot of software.  Adding other features would add to the cost and very few people would use them.  I am concerned about how many people would buy this card.  Even so, I have started to lay out the components.

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12 hours ago, reifsnyderb said:

@Faicuai

 

I am thinking about how the VBXE and Rapidius add a lot to the Atari but I don't think there's much developed that can use those to their full potential.  Making a battery backed up 4 MB Axlon card can be used by a lot of software.  Adding other features would add to the cost and very few people would use them.  I am concerned about how many people would buy this card.  Even so, I have started to lay out the components.

 

Do it smart, design it big with a single main-board concept, but easily to populate or depopulate to fit several user configs. during production (and thus price-points).

 

The thing is that the 800 has a freaking ton of space inside and easy to access (by design), whereas the 400 is more limited, thus choosing board-dimensions and density a bit of a challenge if only one-PCB type is desired for all.

 

Be the king of the hill! 😉💪

Edited by Faicuai
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Ok.  Here's The Mega 4.  Assuming it works, it will have a total of 4,128k of SRAM and will work in the 2nd RAM slot on an Atari 800.  This is 32k of base memory plus 4,096k of Axlon compatible memory.  The base memory will total 48k, of course, as 16k is in the banking window.  I took the 1056 board schematic and added 3 more AS6C8008's with the appropriate chips to control it.  Also added is the capability to add a battery so that the Axlon compatible memory is non-volatile.  On the opposite side of the board are pins that can be jumped so as to allow the board to operate without the DS1210 or DS1312.  Also, there are two contacts for which wires to an external battery could be attached.

 

2116142276_TheMega4.thumb.JPG.60cce75698acec511afe02df6e0c5105.JPG

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Quote

I am thinking about how the VBXE and Rapidius add a lot to the Atari but I don't think there's much developed that can use those to their full potential.

 

Oh well, you know I think everyone has the same thoughts, which are - the VBXE software list isn't tremendous, meaning the games that require VBXE.  Or the games written to only run on Rapidus - not a big list.

 

However, my 130XE has a VBXE and Rapidus.  THe last time I compiled my project, without Rapidus it took 2 minutes, and with Rapidus took 40s.

 

That was a while ago, when I did the test, now the project is so large that I must split it into 3 files, or its too large for the editor.  So lets say, without Rapidus its now a 5 minute compile, and with Rapidus,1 min. 40s - that makes a big difference.

And the rapidus probably speeds up any compiler, not just mine - literally dozens of compilers.

 

The VBXE, i use it with Ken Siders, Kedit, the E: editor.   Works great.  And any E: capable 80 col program would benefit.

 

It's always about the games, never about the computer, it seems.... but if you are converting a tune from one format to another, the rapidus helps.  If you are archiving, the rapidus helps.  If you are crunching a spreadsheet, the rapidus helps.  If you are doing advanced machine learning, good luck...haha, whoops, dial it back , dial it back...

 

anyway - everyone knows the score I guess, but just when someone wants their ultimate atari, it's gotta have certain things, I nice keyboard, a nice display - speed....and so on and so forth.

 

anyway, I would be totally chomping at the bit to purchase that system with 4mb battery backed ram, bit3 card, and 14mhz accelerator.

 

 

 

 

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I have kept my original 800 stock except for swapping out faulty memory cards and have liked it that way, and haven't really sought out "upgrades" for it. I'll probably get this if you decide to make 'em. Compared to the 48k this is like, "Mother of God" lol The non-volatility sounds intersting...

Edited by invisible kid
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10 hours ago, reifsnyderb said:

Ok.  Here's The Mega 4.  Assuming it works, it will have a total of 4,128k of SRAM and will work in the 2nd RAM slot on an Atari 800.  This is 32k of base memory plus 4,096k of Axlon compatible memory.  The base memory will total 48k, of course, as 16k is in the banking window.  I took the 1056 board schematic and added 3 more AS6C8008's with the appropriate chips to control it.  Also added is the capability to add a battery so that the Axlon compatible memory is non-volatile.  On the opposite side of the board are pins that can be jumped so as to allow the board to operate without the DS1210 or DS1312.  Also, there are two contacts for which wires to an external battery could be attached.

 

2116142276_TheMega4.thumb.JPG.60cce75698acec511afe02df6e0c5105.JPG

 

"Mega 4"

 

Perfect name !! 💪💪

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