64K Atari 800

[ClausB]

Hey, Claus! I went to LCC for a year and spent some summers in East Lansing before that at my dad's. I recall a place called (I think) the Computer Castle. It was on Grand River or Saginaw. Do you recall that?

There was Castle Communications on E. Michigan in Lansing in '82 or '83. I knew Rob there - he was at New Dimensions in Computing (on Grand River in East Lansing) before that when he got me into Ataris.

[IndyJones1023]

Ahh, that must be it. I think I bought Ultima (forget which one) from them for the 800. The good old days.

[Atari Smeghead]

Michigan Atari Computer Enthusiasts was a Detroit-area club with hundreds of members. I was in a smaller club in Lansing, called CHAOS, but some of us made the 1.5 hour drive to a few MACE meetings. They were spectacular - filled an auditorium with a big screen projection TV up front!

 

Wow... what a small world. I think I know you, Claus! I was a regular member of CHAOS, from Fosters Community Center to that building in MSU... in fact, I was one of the final members at the end of CHAOS's lifecycle, in the basement of the bank at Saginaw and Abbott. You might not remember me (Randy) but you'll undoubtedly remember Malcolm, John Lewis and Guy. I still see them from time to time.

 

Hey, check this out! I still have an old keychain from CHAOS. The pen doesn't work anymore, however.

 

 

Take care,

Randy

[ClausB]

I was a regular member of CHAOS, from Fosters Community Center to that building in MSU... in fact, I was one of the final members at the end of CHAOS's lifecycle, in the basement of the bank at Saginaw and Abbott. You might not remember me (Randy) but you'll undoubtedly remember Malcolm, John Lewis and Guy. I still see them from time to time.

Hi, Randy! I'm bad with names but I might remember your face. Was Guy the founder and first president? I forgot his name too. Please say hello when you see them next. Maybe we should do a CHAOS reunion dinner. What do you think?

[fibrewire]

Claus, does your 64K upgrade mentioned in post #5 require the use of PortB?

Also, does this 64K mod enable the Atari 800 to use XL/XE only software?

[sloopy]

Claus, does your 64K upgrade mentioned in post #5 require the use of PortB?

Also, does this 64K mod enable the Atari 800 to use XL/XE only software?

 

no, and no... this just fills the memory space with ram, the PIA isnt used as the toggle for selecting ROM/RAM in this...

 

sloopy.

[fibrewire]

I don't suppose it's possible to put an onboard PIA + RAM in a slot , and keep PortB separate?

[sloopy]

I don't suppose it's possible to put an onboard PIA + RAM in a slot , and keep PortB separate?

 

if you add a second PIA, it still wouldnt be XL/XE compatible... but if you just want the extra ram in the upper 16K(-2k) Page, use Claus design in post #5, doesnt need the second PIA, and relatively easy to implement....

 

if you are aiming for XL/XE compatibility, wait for candle or warerat to finish their solutions, and buy one...

 

(you could also, if the fever hits and want something soon, pay someone gobs of money to make you an XL/XE compatible 800)

 

sloopy.

[Chris Strong]

Hey Claus! I remember doing your memory upgrades for the 800 in the mid 1980s.

 

Did you do the Axlon-compatible 256K upgrade for the 800, or was it just based on your 64K upgrade? I can't remember, but I did both for a lot of people.

[ClausB]

I never published any upgrade for the 800 back then, just the 48/64K upgrade for the 400 in MACE and the 256K upgrade for the 800XL in BYTE. Which upgrades did you build? Were you in CHAOS?

[Madi]

Continued...

 

The idea of copying cartridge programs out of ROM and into the top of 48K RAM had been around for a while. Atari was countering this practice by adding code that randomly wrote into the ROM address space so that, if it were running in RAM, the program would destroy itself and crash the system. I thought I could use the write-protected RAM trick in the cartridge address space to thwart that, so I made the "SoftCart" circuit attached.

 

Plugged into the left cart slot, this 2-chip circuit enables RAM on power-up. You would then load the cart program into RAM, write to an address in page $D5 to write-protect the RAM, and restart the system. When it comes up, it thinks it has a ROM cart and runs it normally. How cool was that? No more swapping carts in and out, no more power down and power up cycles, just boot a disk that could hold 10 8K cartridge programs - games, BASIC, etc. It was great. A few months later a product appeared, called The Pill, I think, that did something similar. Opportunity lost.

 

That's as far as I took the 800 upgrades. Later, when I got an 800XL, the RAM upgrade bug bit me again. That story has been covered in the "RAM Upgrade Applications" thread.

 

Fin.

 

Hi ClausB

I have several questions regarding the schematic and the PCB design

 

1. What type of the capacitor used. Is it just a ceramic (filtering) or electrolytic?

2. What type of diode that is used for protection ? small signal, schottky, zener etc.

3. Is it possible to add LED(s) to show switching of RD4 (and or) RD5 ?. This might be difficult, as CTTL (D5xx) might only select RD4/RD5 during writing only.

4. What is the purpose of the 7404 segment #1 (pin 1,2,3) where Phase 2 clock is connected?

5. Do you happen to have the software?

I have cleaned the schematics to make it clear.. Attached

Thank you in advance.

madi

[ClausB]

Nice drawing!

1. It's not electrolytic but I'm not sure of the type, because I took it from that cut up 8K board.

2. That's not a diode. It's a bypass cap, also 0.1 uf and also from the cut board. It goes between +5V and Gnd and does not appear on the schematic.

3. You can add LEDs to the Q outputs of the '74. If you use a 74LS74, Q can sink 8 mA. The 74LS02 input needs < 1 mA so you have 7 mA for the LED.

4. That inverts Phi2 so the the '74 clocks while -CCTL is valid.

5. I'll have a look for the software.

[ClausB]

3. If your LED is 1.5V then you have to drop about 3V across a resistor. The resistor value would be 3V / 7mA = 430 Ohms. Use 470 Ohms. So wire the high side of the LED to +5V, the low side to the resistor, and the other end of the resistor to Q.

[Madi]

2. That's not a diode. It's a bypass cap, also 0.1 uf and also from the cut board. It goes between +5V and Gnd and does not appear on the schematic.

 

You are right.

The Glass/Polystyrene capacitor is a product of the 70’s and early 80’s.

Just waiting for the software.

It will be appreciated if someone is willing to share a copy of the Super Pill software. I hope it will work.

madi

[BillC]

I don't know about the Super Pill, but ATRs of The Pill software are available here.

[ClausB]

I'll look for the software Sunday after I get back from VCFMW.

 

I doubt the Pill software will work. I built this thing months before the Pill came out and have no idea how that one works. This one works simply by reading $D57F to write protect the top 8K of RAM or $D5FF to re-enable it.

[ClausB]

I looked and found some source code for a post-load routine that was appended to the 8K cart ROM file. It assumes that the top 1K of the cart code was shifted down by 8K so that it would not overwrite the screen when loaded. It checks the cart flags to see whether it will boot DOS and, if so, displays a prompt to insert a DOS disk (because my cart copies loaded from a custom boot loader, not DOS). Then it copies the top 1K up, overwriting the screen, does STA $D50F to write-protect the upper 8K, and jumps the the OS coldstart vector. The computer boots up thinking a ROM cart is in place.

 

I could not find any code to create the shifted file plus appendage, so I must have done it manually in the day, using Assembler/Editor DEBUG mode as I often did for such hacks.

 

I can post that source if you like but it's far from a finished utility.

[Madi]

 

I can post that source if you like but it's far from a finished utility.

It would be kind of you to post the source.

------------------------------------------------------

I was hoping for some sort of help from the IMPERSONATOR cartridge as it looked switch-less:

I also looked at the software disk, but I was disappointed.

I couldn't find any reference to CCTL (D5XX) addressing at all in the dumped basic.

The picture (not very clear) also indicated that three pins are connected from this side (RD4, GND and R/W) with a single chip.

No picture of the other side is available to confirm that it has one chip only.

Any how, according to instructions, the dumped CAR is to be loaded and then once the Impersonator cart is inserted the CAR will run.

I wonder, by inserting the IMERSONATOR cart while the program in memory, doesn't that cause the computer to lockup?

 

Note 1: The Assembly source of the code attached to the dumped CART is included as a text file for any one who might be interested.

Note 2 : I guess the switchless SuperPill would be the same as the IMPERSONATOR.

 

madi

altirra imersonator assembly.txt

[ClausB]

Here:

0100  *=$2324
0110 START=*
0120 OFFSET=$9B8D-START
0130 INI LDA $9FFD
0140  AND #1
0150  BEQ F
0160  LDA #DLIST+OFFSET&$FF
0170  STA $230
0180  LDA #DLIST+OFFSET/$100
0190  STA $231
0200 E LDA $D01F
0210  AND #1
0220  BNE E
0230 F LDX #0
0240 C LDA $9C00,X
0250  STA $BC00,X
0260  LDA $9D00,X
0270  STA $BD00,X
0280  LDA $9E00,X
0290  STA $BE00,X
0300  LDA $9F00,X
0310  STA $BF00,X
0320  INX
0330  BNE C
0340  STA $D50F
0350  JMP $E477
0360 MESS .BYTE ".insert.dos.disk.and.....press.start...."
0370 DLIST .BYTE $70,$70,$70,$47
0380  .WORD MESS+OFFSET
0390  .BYTE $07,$41
0400  .WORD DLIST+OFFSET