Self Test issue

[dazpants1]

Hi,

 

I have recently changed the memory on an 800xl because it was showing as bad in self test and the computer would also boot to self test when switching on.

 

Now the computer has new memory and the self test shows the memory as good, but the computer still always boots to self test and not the "Ready" prompt.

 

I can load cartridges and even load cassettes (holding down option + start) and the games work fine.

 

I think it may be the OS chip but could do with an expert opinion.

 

Can anyone help?

 

Ta

 

Daz

[KubaCZ]

Maybe 8k ROM which is holding basic is dead - it's the smaller one. Take it out of socket and try to clean it. If you have (E)EPROM programmer then you can try reading it and comparing it with basic.rom files you can find on net. If it's okay then it can be other things = I can't help here.

 

Also try to load cassete without pressing option - just press start, and see if it loads normally...

 

Edit: This is only true if you have stock XL OS, not the one with inverted basic loading or something like that.

Edited April 21, 2012 by KubaCZ

[dazpants1]

I have seen E EPROM programmers on ebay. Is there a specific type the would be used to program or check the basic chip?

 

Ta

 

Daz

[KubaCZ]

For OS 27128 ROM is used, for basic I thought that it's 2764, but that has more pins...I'm sure somebody here knows.

 

 

But I think it's not worth buying for testing just one chip

[Rybags]

Turn on the Atari without cart and without holding Option.

 

When it goes to Self Test, select Memory Test and let it run. Tell us if there's 40 or 48 small blocks.

 

Could be the Rom isn't being selected or there's an MMU problem or a connection problem somewhere in the system.

 

Lifting up the Basic Rom then pushing it back down might make it work again. Basic Rom is smaller of the 2 chips at the top right.

Edited April 22, 2012 by Rybags

[dazpants1]

@Rybags - I see 40 green squares in the self test. I presume this means that there is a problem. I have not tried to remove the basic chip yet. Because i have replaced the memory chips, it may be i need to check theses are in correctly.

 

@KubacZ - I like the idea of progrmming the EEPROM chips for the OS, i think i would like to learn more about this.

[BillC]

For OS 27128 ROM is used, for basic I thought that it's 2764, but that has more pins...I'm sure somebody here knows.

 

 

But I think it's not worth buying for testing just one chip

Atari BASIC is a 2364 which isn't 2764 compatible. The information needed to adapt a 2764 as a replacement is available at VIC20 Denial, or an adapter board can be purchased for $1.50(bare board)/$4.99(complete unit) at Retro Innovations.

[KubaCZ]

@Rybags - I see 40 green squares in the self test. I presume this means that there is a problem. I have not tried to remove the basic chip yet. Because i have replaced the memory chips, it may be i need to check theses are in correctly.

 

@KubacZ - I like the idea of progrmming the EEPROM chips for the OS, i think i would like to learn more about this.

 

Having alternative OS is good when you have atleast 320kB of RAM, I have 27512 in most of my upgraded Ataris, where I have: speeded XL OS, QMEG 4.04, stock OS and 800-B OS. Firstly I thought that it's too much upgrades for one Atari, but now I can't imagine loading everything at 19200b

[Rybags]

Going to Self-test instead of Basic and getting 40 squares, I suspect the memory select logic is working fine but the Basic Rom itself isn't returning data, so the thing to try would be lift and reseat the Basic Rom.

 

The Ram you've replaced should be fine, so don't worry about it. Each chip supplies 1 bit for every byte for all 64K, so if you did something wrong there you'd soon know about it.

[dazpants1]

Ok tonight, i'm going to reseat the basic chip.

[dazpants1]

OK with option held down i get 48 blocks in self test. I've just noticed that the U4 Basic chip is probably the only chip that is soldered in...oh CR*P.

 

Looks like i will need to replace the chip altogether.

 

Ta

 

Daz

[+bob1200xl]

The BASIC chip could be bad or, you could have a bad MMU. Try the MMU (CO61618) if it is socketed. You should have one in your 130XE.

 

Bob

[dazpants1]

@bob1200xl - Unfortunately they are all soldered, so i looks like i need to get the soldering iron out again lol.

 

Just for my knowledge what does 40 or 48 small blocks mean in the self test. Which is normal for a 800xl?

 

Ta

 

Daz

[+bob1200xl]

The blocks represent 1K of memory. 40 blocks means that BASIC is enabled and overlays (disables) 8K of memory. The OS and hardware overlays another 16K of memory, leaving you with 40 blocks available. If BASIC is disabled, you should test 48 blocks of memory. So, if you get 48 blocks when you hold OPTION down during poweron and you get 40 blocks if you do not hold down OPTION, BASIC is being enabled correctly - it just isn't working.

 

Bob

[dazpants1]

@bob1200xl - Thats really interesting stuff, i just need to sort out this basic problem an i'm up and running again.

[spookt]

Hey Daz

 

Nice to see another Atari 8 bitter in the UK!

 

If you need any help replacing your BASIC chip let me know. I'm up in Darlington, not a million miles away. I'll have a couple of spare chips kicking around and if you don't feel up to removing the original and socketing it, I can give you a hand.

 

Paul

[dazpants1]

Hi Paul,

 

That sound like a plan. IM sent.

[suspicious_milk]

Sorry to resurrect such an old thread, but I just picked up an 800xl rev D off eBay, and it's having the exact same problem. Did a quick search and landed here.

 

So, if you get 48 blocks when you hold OPTION down during poweron and you get 40 blocks if you do not hold down OPTION, BASIC is being enabled correctly - it just isn't working.

 

However, mine gets 40 blocks no matter wether OPTION is held or not. I tried pulling and cleaning the MMU (the only socketed chip on the board), which didn't change anything. All 40 blocks are green, no errors, and like the OP's XL it boots cassette/disk/cart just peachy keen. Since holding the option at boot doesn't change anything, does that mean the OPTION key is stuck internally? Bad MMU, RAM, or Basic ROM?

 

Since the BASIC ROM is not socketed, and I have no extra 800xl keyboard, would I be wasting my time swapping out the MMU (my 65xe may have a socketed one)?

 

Any tips appreciated.

[Rybags]

I take it you can start games OK - most use Option in some way.

 

Self-Test has the keyboard test, it should register Option if you press it. To disable Basic Option has to be held pretty much from when you power up to when you see the blue screen.

 

If you can get Basic prompt, you can just do: 10 ? PEEK(53279) : GOTO 10

That will show the console key state, values should read from 0-7 depending on which console keys you hold.

[suspicious_milk]

Thanks. The Option key isn't stuck - - it works in the keyboard test.

I guess, I'll try to order an MMU or pickup a busted unit somewhere. If it's basic rom, it's high time I practice/try my hand at soldering anyways. This isn't my main unit so it's not like I'm down.

[Rybags]

Does it go to Basic if powered up, no key, no peripheral?

 

If you can get to Basic, try this in Basic (power up without peripheral) -

 

POKE 1016,1

 

Then press Reset, it should then goto Self Test with Basic disabled and give 48K worth of Ram Test.

[suspicious_milk]

Does it go to Basic if powered up, no key, no peripheral?

 

If you can get to Basic, try this in Basic (power up without peripheral) -

 

POKE 1016,1

 

Then press Reset, it should then goto Self Test with Basic disabled and give 48K worth of Ram Test.

 

No, thats the problem. It doesn't go to basic no matter what. With nothing attached, it goes to SELF TEST. It boots properly from disk/tape/cart. Runs games just fine. In SELF TEST, regardless of wether OPTION was held in or you just simply turn it on, the RAM tests shows 40 green blocks. I reckon its the MMU, but suppose it could be the BASIC ROM. At this point, only one way to find out (as far as I know).

 

EDIT... I don't have a BASIC cart. My other Atari's are XE models, all with REV C built in. I could just boot BASIC from a disk . . . may try that tomorrow, my XEgs is all hooked back up for now ;0)

Edited December 14, 2012 by suspicious_milk

[Rybags]

I doubt Basic would boot from disk - the Ram is being disabled where it needs to load.

 

I'd have to agree it's probably the MMU then, or a problem with the signal going to it. There's the RD5 line that you might want to check. It tells the MMU if there's a cart inserted that wants to occupy $A000-$BFFF.

 

You could do some quick checks with a multimeter on the MMU - http://www.atarimax.com/jindroush.atari.org/achmmu.html

 

RD4 and RD5 pins should read low - if cart is inserted one or both go high.

/BE is an input which reflects whether Basic Rom is enabled - should read low if Basic enabled, high if disabled.

 

You could also check the Pin 11 output of the PIA - that's PORTB Bit 1 which goes to /BE, status rules the same.

[+tf_hh]

Hi,

 

is there an original ROM in the operating system slot (28 pin, under the BASIC ROM) or it´s an EPROM? If so, perhaps there a special patched version with changed OPTION meaning (you´ve to hold down OPTION to enter BASIC, if OPTION is not held, the OS boots without BASIC). Or it was an EPROM with two operating systems (for example: OLD-OS from 400/800, with this one XL-onboard-BASIC normally not works) burned and the switch was missing or anything like this.

 

The probability of a defective BASIC ROM is very, very low. Also a bad MMU could happen, but normally the system doesn´t boot when it´s gone. This defective from my experience is mostly a defective PIA (6520), burned by joystick-port experiements or something like that

 

Good luck, Jurgen

[suspicious_milk]

I doubt Basic would boot from disk - the Ram is being disabled where it needs to load.

 

I'd have to agree it's probably the MMU then, or a problem with the signal going to it. There's the RD5 line that you might want to check. It tells the MMU if there's a cart inserted that wants to occupy $A000-$BFFF.

 

You could do some quick checks with a multimeter on the MMU - http://www.atarimax....org/achmmu.html

 

RD4 and RD5 pins should read low - if cart is inserted one or both go high.

/BE is an input which reflects whether Basic Rom is enabled - should read low if Basic enabled, high if disabled.

 

You could also check the Pin 11 output of the PIA - that's PORTB Bit 1 which goes to /BE, status rules the same.

 

Thanks guys.

 

Well, I've got a little el-cheap-o mutltimeter and not to sure how to use it. I put in what I believe is ohm/resistance and checked* the pins R4, R5, and /BE. The numbers on the mm seemed steady without the cart but with a cart I got a lot of fluctuation. (Sorry, my ignorance is showing).

 

*by checked I mean I jammed the red and black pointy things on the same pin in question

 

I did have some fun sticking on other chips and watching screen artifacts ;0) (like a monkey with fire, here)

 

However, I was in error in my earlier posts when I said carts/tapes/games run fine. They do not run fine. Most start. Space Invader cartridge plays normal until you get killed then freezes. Dark Chambers ATR SIO2SD play perfect, but all items and characters are now just solid squares. Really weird stuff. Earlier, I'd just loaded, did a quick 2 second glance, and said all was good. My fault for not looking further.

 

It's starting to to look like bad RAM somewhere to me?