AXLON 48K upgrade for a 400?

[+bob1200xl]

I was looking at a 400 on my bench and I noticed that there was a little add-on PCB on the main board. Said AXLON on it. Checked the memory card and saw 64K DRAMs. Power up and FRE(0) gives me 37K+.

 

No added wires, just the little PCB.

 

Never seen anything like this - very nice. Is it common?

 

Bob

 

 

[fibrewire]

We were discussing this very board a while back. I wanted to know if this was adaptable for use in slot 1 of the Atari 800. Also, you are the only other person I've come across that has one.

Edited July 1, 2014 by fibrewire

[Rybags]

I thought any memory >32K on the 400 needed at least some modification.

 

The thread on 800 memory selection by ClausB explains how the 800 selects and passes on the lines that select each bank of 8K http://atariage.com/forums/topic/177885-atari-800-ram-selection/page-5?hl=%2Bmemory&do=findComment&comment=2801326

 

I don't think modules >32K work on the 800 either without modification to the machine, he states that each slot has 5 select lines in which would allow only 40K.

[BillC]

Intec made a similar board that was placed under the 400 main board for use with their 48K RAM upgrade, they must serve the same purpose as the jumper wires used with the Atari 400 48K upgrade board. Below is a link to a post made about the Intec upgrade.

http://atariage.com/forums/topic/207429-atari-400-incognito-like-upgrade/page-5?do=findComment&comment=2939447

[Rybags]

Bob - but is it a true 64K upgrade with the 4K window @ $C000 ?

 

Maybe try:

 

POKE 106,200 : GR. 0

[ClausB]

Cool! Would you also photograph the RAM board, front and back, so we can see how it works?

[+bob1200xl]

There is no RAM at $C000.

 

POKE gives me screen garbage/black screen. Is that a CTIA test?

 

It's a GTIA with a 6502 CPU.

 

Bob

 

 

 

Bob - but is it a true 64K upgrade with the 4K window @ $C000 ?

 

Maybe try:

 

POKE 106,200 : GR. 0

[+bob1200xl]

Cool! Would you also photograph the RAM board, front and back, so we can see how it works?

 

 

Sure:

 

 

[ClausB]

As far as I can see, the small board passes A15, A14, and S4 to the RAM board. So it could be only a 40K board. I don't see S5 being passed and I don't see any RAM deselect circuit, so it would conflict with a 16K cart. With no cart it would still be only 40K.

 

Bob, could you boot DOS with no cart and see how much RAM you get? Could you also probe pin 6 (S5) of the 74LS42 on the small board to see if it connects to any of pins 1-4 of the male DIP.

[+bob1200xl]

It looks like pin 6 connects to pin 6. If you look closely at the board, pin 14 is floating. They cut the trace near the IC pin.

 

An AW cart fails.

 

How do I tell how much memory I have with no cart?

 

Bob

[russg]

It looks like pin 6 connects to pin 6. If you look closely at the board, pin 14 is floating. They cut the trace near the IC pin.

 

An AW cart fails.

 

How do I tell how much memory I have with no cart?

 

Bob

run SHORTEST.COM

 

..... shoot. SHORTEST.COM returns 65535 with 48K OS B in Altirra. I may have time to get back with another memory tester. Or maybe you already know one.

 

Here's a ATR with MEMCHECK.COM. and a bunch of other memory checkers. On a MyDOS 4.5 atr.

MEMCHECK.COM detected 48k OS B OK in atari800winplus 4.

 

Yeah, MOMCHECK.COM will work. Ignore the rest.

..... MEMCHECK.COM works on a 48K 800. It doesn't work on 32k or 16k. Maybe someone else has a better binary load checker. It might work with 40k, I have no way to test that, probably won't.

I checked on a DOS 2.0S ATR so it would load DOS with 16K. DOS boots but MEMCHECK doesn't work, garbled screen.

SHORTEST.zip

MEMRAMCHECKTEST.zip

Edited July 1, 2014 by russg

[ClausB]

Yes, I see the cut trace but I also see a jumper under the chip. Can you check that the jumper connects 14 to 14? If not, then the whole computer would not work, I think.

[+bob1200xl]

Yes, pin 14 of the LS42 goes to pin 14 of the header and pin 1 of the header.

 

Bob

[fibrewire]

Only 40K is available with the Rampower 48 board and the small IC module installed. Apparently there was a cartridge key that makes the full 48K available. If one didn't want to mess with the cartridge board, there was a resistor that was moved to a different position on the Axlon 48K board, and a jumper wire attached to pin 1 and pin 13 under the cartridge socket. See attached scan from the manual.

Axlon 48K Plus.pdf