4-in-1 OS Anomoly

[+Larry]

I've made several 4-in-1 OS modules using 27C512 (ST) eproms. Today I made a new one, and only the first OS works. For the others I get the dark "green screen" when the power is turned on, then nothing -- no boot. I put the OS's together using a Hex editor:

$0000-3FFF

$4000-7FFF

$8000-BFFF

$C000-FFFF

 

And all the individual OS files were "known good." I read back the eprom (burned) file and it verifies to the original file used to make the eprom.

 

The eprom verifies erased, then verifies to the buffer after burning. But it doesn't work. To test it, I took another Atari with the same type 4-in-1 (that I made some time ago), and it's eprom works in the "new" computer I'm working on. Then I took the "new" eprom and put it into the other computer, and it does not work.

 

So I must have a bad eprom. (?) The weird thing other than verifying "good" in the burner is that this is the same brand and group/lot of eproms that I used before. I'm going to toss it try another, but this is strange -- has anyone else encountered this? I've had eproms that wouldn't erase and eproms that couldn't be programmed, and different brands/speeds of eproms that didn't work in various devices, but nothing quite like this.

 

-Larry

[+bob1200xl]

Cockpit trouble...

 

 

(you need to use DOS 2.0!)

 

 

Bob

 

 

 

I've made several 4-in-1 OS modules using 27C512 (ST) eproms. Today I made a new one, and only the first OS works. For the others I get the dark "green screen" when the power is turned on, then nothing -- no boot. I put the OS's together using a Hex editor:

$0000-3FFF

$4000-7FFF

$8000-BFFF

$C000-FFFF

 

And all the individual OS files were "known good." I read back the eprom (burned) file and it verifies to the original file used to make the eprom.

 

The eprom verifies erased, then verifies to the buffer after burning. But it doesn't work. To test it, I took another Atari with the same type 4-in-1 (that I made some time ago), and it's eprom works in the "new" computer I'm working on. Then I took the "new" eprom and put it into the other computer, and it does not work.

 

So I must have a bad eprom. (?) The weird thing other than verifying "good" in the burner is that this is the same brand and group/lot of eproms that I used before. I'm going to toss it try another, but this is strange -- has anyone else encountered this? I've had eproms that wouldn't erase and eproms that couldn't be programmed, and different brands/speeds of eproms that didn't work in various devices, but nothing quite like this.

 

-Larry

[+bob1200xl]

Try dumping the old 27C512 that works and burning that into your 'bad' EPROM. (after you erase it) You may have crossed your hands when you did the hex edit... It's not likely that the burner would verify if the code was good.

 

Bob

 

 

 

I've made several 4-in-1 OS modules using 27C512 (ST) eproms. Today I made a new one, and only the first OS works. For the others I get the dark "green screen" when the power is turned on, then nothing -- no boot. I put the OS's together using a Hex editor:

$0000-3FFF

$4000-7FFF

$8000-BFFF

$C000-FFFF

 

And all the individual OS files were "known good." I read back the eprom (burned) file and it verifies to the original file used to make the eprom.

 

The eprom verifies erased, then verifies to the buffer after burning. But it doesn't work. To test it, I took another Atari with the same type 4-in-1 (that I made some time ago), and it's eprom works in the "new" computer I'm working on. Then I took the "new" eprom and put it into the other computer, and it does not work.

 

So I must have a bad eprom. (?) The weird thing other than verifying "good" in the burner is that this is the same brand and group/lot of eproms that I used before. I'm going to toss it try another, but this is strange -- has anyone else encountered this? I've had eproms that wouldn't erase and eproms that couldn't be programmed, and different brands/speeds of eproms that didn't work in various devices, but nothing quite like this.

 

-Larry

[+Larry]

Good idea -- I'll give that a try.

I'll take the Dos 2 suggestion under advisement...

 

-Larry

 

 

Try dumping the old 27C512 that works and burning that into your 'bad' EPROM. (after you erase it) You may have crossed your hands when you did the hex edit... It's not likely that the burner would verify if the code was good.

Bob

[Alphasys]

To me this sounds like a pull-up resistor problem. Since only the 00 base works. Maybe forgot to hook up the +5V on the pull-up resistors? Or maybe the resistors themselves are too high a value? I've primarily used 10k ohm resistors for this kind of job.

[+bf2k+]

 

So I must have a bad eprom. (?) The weird thing other than verifying "good" in the burner is that this is the same brand and group/lot of eproms that I used before. I'm going to toss it try another, but this is strange -- has anyone else encountered this? I've had eproms that wouldn't erase and eproms that couldn't be programmed, and different brands/speeds of eproms that didn't work in various devices, but nothing quite like this.

 

Not exactly the same thing but I've burned MIO EPROMs that would actually change values in front of my eyes - they were definitely bad.

[santosp]

@ Larry

 

And for the history, what type OS you burn in your eprom? I have a 130XE, and I want your opinion about what OS's must be use. For example OSA OSB QMEG and stock XE?

[+Larry]

Nothing real special:

 

Stock XL/XE

XL/XE with Hias' SIO Patch

Omnimon XL

MyIDE 4.3E (external MyIDE)

 

I'm still flogging this problem, but I have found errors in the 4-in-1 .bin file. I haven't a clue how -- it was just copy and paste, but they are there, so I'm verifying each before and after it is added to the compound file.

 

-Larry

 

@ Larry

 

And for the history, what type OS you burn in your eprom? I have a 130XE, and I want your opinion about what OS's must be use. For example OSA OSB QMEG and stock XE?

[+bob1200xl]

It's because you didn't use DOS 2.0...

 

Bob

 

Nothing real special:

 

Stock XL/XE

XL/XE with Hias' SIO Patch

Omnimon XL

MyIDE 4.3E (external MyIDE)

 

I'm still flogging this problem, but I have found errors in the 4-in-1 .bin file. I haven't a clue how -- it was just copy and paste, but they are there, so I'm verifying each before and after it is added to the compound file.

 

-Larry

 

@ Larry

 

And for the history, what type OS you burn in your eprom? I have a 130XE, and I want your opinion about what OS's must be use. For example OSA OSB QMEG and stock XE?

[+Larry]

Got it!

 

I downloaded a different hex editor (HxD) and did file compares as I "built" the 4-in-1 file, and the reprogrammed "bad eprom" came up perfectly for all four OS. I'm certainly not blaming the previous Hex Editor -- as I said, I don't have a clue what went wrong. But the newer one has more features, anyway.

 

BTW, the wiring I use for the 4-in-1 has no pull-ups. I ran into this one some years ago and just have always used it.

It's wired like this (DPDT mini switches):

 

SW1 SW2

+5 +5

P27 P1 (Pin 27 and Pin 1 out of socket)

Gnd Gnd

 

Thanks to everyone for their comments and suggestions.

 

-Larry

[+bob1200xl]

The practice in old TTL circuits was to use a pull-up resistor to tie an input active. The requirement was 2.4v or higher and .6v or lower for logic levels, so they used ground or a resistor to +5v. The input was an emitter leg of a transistor, which is reverse biased and does not draw much current when active. With CMOS, like your EPROM, you see inputs tied directly to +5v.

 

So, you can use pull-up resistors or not...

 

But... if you are using switches like that, be certain that they break-before-make or you'll short out your power supply during switch transitions. Should not be a problem - just makes me nervous.

 

Bob

 

Got it!

 

I downloaded a different hex editor (HxD) and did file compares as I "built" the 4-in-1 file, and the reprogrammed "bad eprom" came up perfectly for all four OS. I'm certainly not blaming the previous Hex Editor -- as I said, I don't have a clue what went wrong. But the newer one has more features, anyway.

 

BTW, the wiring I use for the 4-in-1 has no pull-ups. I ran into this one some years ago and just have always used it.

It's wired like this (DPDT mini switches):

 

SW1 SW2

+5 +5

P27 P1 (Pin 27 and Pin 1 out of socket)

Gnd Gnd

 

Thanks to everyone for their comments and suggestions.

 

-Larry

[+Larry]

OK, I've never had any issues, but better safe than... Is there a way to check using a VOM or DVOM -- perhaps using continuity?

 

And how about posting a better circuit for the job? Can you do it without pull-ups?

 

-Larry

 

(snip...)

But... if you are using switches like that, be certain that they break-before-make or you'll short out your power supply during switch transitions. Should not be a problem - just makes me nervous.

 

Bob

[Fox-1 / mnx]

But... if you are using switches like that, be certain that they break-before-make or you'll short out your power supply during switch transitions.

 

And DOS 2.0 has no protection for that? :-)

[+bob1200xl]

The effect would be momentary, never see it on a meter. The switches should be (are normally) designed as break-before-make - it's the failure mode that is worrisome. The little leaf springs inside can/will crack, shorting out the two poles. You pretty much need to use pull-up resistors to be really safe. Even if the switch poles don't short out, an open switch pole will float the pin, whereas a pull-up will at least drive it to +5v. (so, when your switch gets flakey, you can just tap it to cause a failure - easy to test...) Anyway, you only need three wires to the two switches, rather than four. Save a tree. (or something)

 

It just isn't a good idea to run wired power to any mechanical assembly if you don't have to. Wires break off and short things out, a strand will 'escape' from the main wire - stuff like that. I see upgrades all the time that have individual wires running all over the place, not tied up or bundled. What do you think will happen if one breaks off and wanders all over your motherboard?

 

I agree that you will probably never see a problem with the way you are wired. Neither would I, or a hundred other Atari folks. But, number 101 could have a nasty bug that is hard to find and might be avoided by using pull-up resistors. Imagine someone with a shorted switch - his system will not power up... how long will it be before he suspects/checks the switches, if ever? Would you?

 

I would wire a 1K resistor between +5v and each pin on the bottom of the motherboard. (this may be a problem in some layouts) Run the two pins and a ground wire out to the switches, wire the center pin of both switches to ground and the two address nets to each switch, either pin. Down the road, if you seem to have weird problems, just tap the switches to see if they are going bad on you. (you are using American Made, quality switches, right?)

 

All of this is more work and I don't necessarily follow my own advice when I am hacking around on a m/b. But, on a system that I am going to be using for real, I do.

 

...off my soapbox...

 

Bob

 

 

 

OK, I've never had any issues, but better safe than... Is there a way to check using a VOM or DVOM -- perhaps using continuity?

 

And how about posting a better circuit for the job? Can you do it without pull-ups?

 

-Larry

 

(snip...)

But... if you are using switches like that, be certain that they break-before-make or you'll short out your power supply during switch transitions. Should not be a problem - just makes me nervous.

 

Bob

[+Larry]

Too many "pins" for me to be clear as to what you mean. Could you make a Q&D sketch -- unless you mean literally every pin (and I surely don't think you mean that...)

 

This attached sketch is the other common variant that I've seen, which was posted on the Atarimax forums. Is this along the lines you are describing?

 

-Larry

 

 

 

I would wire a 1K resistor between +5v and each pin on the bottom of the motherboard. (this may be a problem in some layouts) Run the two pins and a ground wire out to the switches, wire the center pin of both switches to ground and the two address nets to each switch, either pin.

 

[+bob1200xl]

Yes - that's it, just the two high address pins. (I normally do a 256K EPROM with only one pin and no resistors if I'm using the RF chan switch on a 1200XL) Except, I use 1K resistors, maybe 3K. Whatever I find first in my trash box... I do not leave the pins out of the socket, however. It's sometimes a pain in the a** to do so, but I cut all the traces to the target pin and wire under the m/b. Not only is it neater and less fragile, but I can swap out the EPROM easily and it can still be used in a socket.

 

Bob

 

 

 

Too many "pins" for me to be clear as to what you mean. Could you make a Q&D sketch -- unless you mean literally every pin (and I surely don't think you mean that...)

 

This attached sketch is the other common variant that I've seen, which was posted on the Atarimax forums. Is this along the lines you are describing?

 

-Larry

 

 

 

I would wire a 1K resistor between +5v and each pin on the bottom of the motherboard. (this may be a problem in some layouts) Run the two pins and a ground wire out to the switches, wire the center pin of both switches to ground and the two address nets to each switch, either pin.

 

[Alphasys]

Wiring the resistors to the open side of the switch saves a bit of current, and works well. You're an idiot if you change OS versions during operation anyway.

[Marius]

Hey!! I made those drawings!!! Cool to see they are still used!

 

@alphasys

Sometimes i switch oses because when i switch off my atari i lose ramdisk content!

[Fox-1 / mnx]

Save a tree. (or something)

 

Eat a beaver...

 

 

You're an idiot if you change OS versions during operation anyway.

 

I know someone who changed a non-socket 65c02 of an 800XL only to discover it was still powered (switched ON) after the operation was completed. No harm done. It started to boot a disk after a reset without any problem :-)

Edited January 17, 2011 by Fox-1 / mnx

[+Larry]

OK, I've reconnected the switches using 5.6K pull-ups (I didn't have any 4.7K). I've seen all kinds of values mentioned for these pull-ups, so I presume there is no one "correct value." (?) All four of the OS come up just fine.

 

BTW, IIRC Dos 1 had the protection for errant switches, but it was left out of Dos 2 to save space...

 

I feel safer already...

 

-Larry