Designing an Axlon compatible board

[ClausB]

Over the full 48K range: A14 = S2 NAND S3

 

But you don't need that because SRAM A14 comes from the bank register when $4000 - $7FFF are accessed. When $0000 - $3FFF and $8000 - $BFFF are accessed, you could use A15 as SRAM A14, and hold SRAM A15 - A18 high. Then bank 30 would always appear at $0000 - $3FFF and bank 31 at $8000 - $BFFF.

[retrocanada76]

I thinking in allow the 64K range, that would need a new OS-ROM/RAM board and running XL BIOS. But basic and auto test would not be present.

 

But then why not go for a RAMBO256 ? But that would require a new middle ram and a new OS-ROM. I don't want to mod the A800 only the boards.

[ClausB]

Yes, supporting the full 64K range is complicated, but covering the 48K range so as to free up slots 1 and 3 is not.

[ClausB]

I suppose it's not necessary to free up slot 1, since that's of no other use than for RAM. But it would be valuable to free up slot 3, since that slot has I/O select signals to support various peripheral cards. Since slot 2 has all the RAM select signals needed for 32K, you would not have to wire A15 from the OS board.

 

Before I continue, let me compliment you on the fine job you have done with this board. I think it's a great way to expand the 800 without breaking into the box.

 

A few minor mods to your circuit would allow bank 31 to appear at $8000 - $BFFF so that no RAM board would be needed in slot 3. First, replace the 74LS273 with a '374, which has the same pinout except for pin 1. Wire pin 1, /OE, to /S2 AND /S3. Next, wire pull-up resistors (between 1k and 10k Ohm) to the '374 output pins 2, 5, 6, 9, and 12, the BANK signals. Finally, wire the SRAM /CE to /S2 AND /S3 AND /S4 AND /S5. That requires either a single 4-input AND gate, 74LS21, or 2 more '08 gates. The idea here is that it works the same as you had it when $4000 - $7FFF are accessed, but when $8000 - $BFFF are accessed the '374 outputs go open and the resistors select bank 31.

[retrocanada76]

Glad someone is looking into my design. Thanks

 

I'm happy with my Axlon and I'm into a new project now what I call "Colleen320". A set of a new Personality and Slot 2 SRAM board freeing slot 1 and 3.

 

Expanding the A800 to full 64K, Dual 16K BIOS and having extra 256KB banked through PORTB. Also, CPU/ANTIC is banked on same CPU bit. If you want to have the good old Atari800 just put back the old boards, no soldering required.

 

I'll share the schematics if you want to help me with any possible bugs before producing a prototype. There are too many wires to make it into protoboard.

 

Producing a board costs around 25 dolares. Less than a good pizza

[retrocanada76]

Actually I was looking into the final board layout and found out I missed the jumpers on N-M, R-P and T-S.

 

Here final version I believe fixed (my protoboard has them all)

Axlon 512 V1.2.zip

Axlon 512.pdf

[sl0re]

The middle board could have the slot3 ram on it, but not the slot1 because the signals needed are not there.

 

But then it would require extra SRAM chip for the 16KB (the smaller I found was 32K SRAM). Trying to use a bank from the ram drive would make the circuit far more complex, also more gates for the extra logic.

 

I'm planning to make a OS-ROM with an Cyclone IV connected to it , then the sky is the limit....

 

Freeing up slot 3 would be really useful. Then we'd have a card slot to play with as a card slot instead of 16k memory holder.

 

PS

Thanks for what you have done already. Very nice.

Edited September 11, 2016 by sl0re

[gozar]

Is there anyway this can work in a 400?

[retrocanada76]

Probably not. Also, I don't have a 400 to test.

 

BTW: I found a bug in my design: the 74LS273 Pin 1 must be high (connected to VCC) it's floating and causing only odd pages to really work.

 

I will fix it in a new gerber, but is easy to patch if someone ordered a board using the old gerbers.

[ClausB]

There's always a way. With some mods, it would work in a 400.

[retrocanada76]

Sure but then it must be a full 48K board and pull the signals from the mobo. Not this board.

[ClausB]

Your board could be modified to do that in a way similar to how I modified an original Axlon 128K to work in a 400:

 

http://atariage.com/forums/topic/242139-axlon-rampower-128-extra-leadswitch/

[tep392]

Did anyone order the PC boards? Have an extra board I could buy?

[tep392]

I just ordered three of these boards. I'm building one for myself and can build the other two to sell if anyone wants one. I'll only ask the cost for parts + shipping. $30+shipping.

[venom4728a]

I would like 1 please.

[tep392]

I would like 1 please.

You got it. I'll contact you after I've built and tested them. It will probably take a few weeks.

[tep392]

I just finished building retrocanada76's RAM board design and it seems to be working as intended. I've modified the Axlon driver that came with Warpspeed DOS XL to support the full 512k. It creates 2 ramdrives D3: and D4: with a capacity of 242K each. Here's some photo's. He mentioned that there was an error in the board layout and the reset pin of the 74LS273 needed to be connected to 5V. I decided to use a simple RC circuit to hold the pin low long enough for the power to stabilize before coming out of reset. This insures the board will start at bank 0 on power-up. Here's a few photo's.

 

[venom4728a]

Looking Good!!

[tep392]

Here's a copy of Warpspeed DOS XL 2.42 with some drivers I've updated to support the 512K Axlon clone and the RAMSCAN memory test program which I have also updated for the 512K board.

 

DOSXL242AX512.ATR

 

edit: These are the custom files I added.

WSAXL256.COM - Creates single ramdrive, D4: with 931 DD sectors. Uses banks $01-$0F

WSAXL512.COM - Creates two ramdrive's, D3: and D4: with 931 DD sector each. Uses banks $01-$0F and $11-$1F. Bank $10 is available for other uses.

SCAN512.COM - This is the Axlon RAM test program modified to test 512K.

[tep392]

I've posted a demo video on youtube.

 

[ebiguy]

On 9/7/2016 at 11:13 PM, retrocanada76 said:

Glad someone is looking into my design. Thanks

 

I'm happy with my Axlon and I'm into a new project now what I call "Colleen320". A set of a new Personality and Slot 2 SRAM board freeing slot 1 and 3.

 

Expanding the A800 to full 64K, Dual 16K BIOS and having extra 256KB banked through PORTB. Also, CPU/ANTIC is banked on same CPU bit. If you want to have the good old Atari800 just put back the old boards, no soldering required.

 

I'll share the schematics if you want to help me with any possible bugs before producing a prototype. There are too many wires to make it into protoboard.

 

Producing a board costs around 25 dolares. Less than a good pizza

I was wondering if you did finish the above expansion Colleen320 ?

 

Also, would you be willing to share the KiCad source files for your Axlon 512 board ?

[Faicuai]

On 10/14/2017 at 10:53 AM, tep392 said:

I've posted a demo video on youtube.

 

 

Not just a simple and great upgrade (should also work with SDX/SIDE)... but also clearly and unquestionably showing the 800's inherent superiority, architecture-wise.

 

A little wire on OS/Board, and the rest is just plug on expansion slots. Can't get any simpler than that!

[Jeffrey Worley]

On 10/2/2017 at 10:45 PM, tep392 said:

I just finished building retrocanada76's RAM board design and it seems to be working as intended. I've modified the Axlon driver that came with Warpspeed DOS XL to support the full 512k. It creates 2 ramdrives D3: and D4: with a capacity of 242K each. Here's some photo's. He mentioned that there was an error in the board layout and the reset pin of the 74LS273 needed to be connected to 5V. I decided to use a simple RC circuit to hold the pin low long enough for the power to stabilize before coming out of reset. This insures the board will start at bank 0 on power-up. Here's a few photo's.

 

Where did you order these from?  I have the parts on the way but for the boards and would like to just duplicate your order instead of taking a chance on a new one.

 

Best,

 

Jeff

[tep392]

On 8/1/2019 at 2:33 PM, Technoid Mutant said:

Where did you order these from?  I have the parts on the way but for the boards and would like to just duplicate your order instead of taking a chance on a new one.

 

Best,

 

Jeff

I can't find my records but I recall having to order a min of 3 boards.  They were about $15 each and I ordered enough parts to build up all three and sold the two extra's.  It might have been OSH Park.  

[Jeffrey Worley]

I ordered ten of these boards from china.  They shipped today and I should have them this week or next.  The rest of the parts are arriving in dribs and drabs over the course of this month.  I should, barring the unforeseen, have ten working boards by the beginning of next month (September 2019).

 

RSVP

YHOSvt.

** TNM **