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Right. Here we go. Chick let 2001

C

Chandler1

Experienced Member
Joined
Mar 24, 2012
Messages
51
Location
London UK
So y'all may remember I bought a 2001, which worked except for low memory, and by swapping the chips around I got 6k or so back, then the screen just changed to garbage.
Well, I bought a pet vet, slotted it in (with new 6502 onboard) and it works perfectly.

The question is, what was most likely wrong, and how do I find out for sure? I'd rather have it working in an original state if I can, but I don't have access to a logic probe or oscilloscope....I checked many of the pins for connectivity, and the voltage rails which were fine. I could finish those continuity checks, I suppose,if it would help, but anywhere particular I should start?

Any ideas? Or do I just use it as is, and always wonder if it was just one faulty ROM.....
Or would anyone be so kind as to check all the roms for me? Tbh, I have no idea how big a job that would be. Finally, I bought a second hand set of roms with identical numbers to those in the pc, but I have no clue on the condition of those chips, and don't want to make it any worse by swapping them in to what is now a working machine.
 
First off what kind of roms and ram do you have?

And what motherboard?

On my 2001 I have 6550 rams and 6450 roms, and I have removed all of them and I'm using a 6502-RAMROM board by Nicolas Welte in it, the heat difference is
amazing, the power transistors have so much less work to do. And having a reset button is great to save on wear and tear.


Later,
dabone
 
Well, if you're really curious and no one closer steps up, you can send me the chips for testing; it doesn't really matter, but yes, it would be nice to know which types they are (there were two types of each, RAMs and ROMs, although Dabone's version was probably the most common).

I have a few spare ROMs but Murphy says they won't be the ones you need.

FWIW, in order to upgrade I replaced the ROMS in one of my 2001s with one of Jim Brain's $6.50 6540 adapters and a few mods and jumpers; will try the same trick with the RAMs one of these days.
 
Chandler1 said:
Well, I bought a pet vet, slotted it in (with new 6502 onboard) and it works perfectly.

The question is, what was most likely wrong, and how do I find out for sure?

Any ideas? Or do I just use it as is, and always wonder if it was just one faulty ROM..... Or would anyone be so kind as to check all the roms for me? Tbh, I have no idea how big a job that would be. Finally, I bought a second hand set of roms with identical numbers to those in the pc, but I have no clue on the condition of those chips, and don't want to make it any worse by swapping them in to what is now a working machine.
Click to expand...

Hi chandler1, If you get comfortable with using the PETVet and uploading new ROM images into it via the serial link, I have a special image that I created with help from Mike that will do a thorough RAM test and CRC16 checksum of the ROM's. It checks the computed value against an internal lookup table of all know ROMS I could find for the PET, so if it's doesn't recognise the checksum, then it is most likely bad.

Rob
 
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Yeah, I thought there was a version of the firmware that let you test the on board RAM & ROMs and it self-installs as well if I'm not mistaken.
 
Hey there,

I was working on a RAM/ROM tester to include with the PETvet, and got as far as being able to read in ROM contents to compare with ROM images in flash memory, but haven't had the free time recently to package it up into usable form. Rob's ROM/RAM tester looks very cool, I haven't had the chance to play with it myself, but it should be able to help track down the culprit.
Another simple test you can do to pinpoint which ROM or ROMs are bad is to selectively exclude different ROM segments from being replaced by the PETvet's memory mapper. If you're interested in trying this, download the firmware bundle (http://bitfixer.com/bf/data/PETvet10.zip) and I can show you how to exclude different segments from the PETvet's memory mapper. Basically you can switch individual ROMs on the mainboard back into use. Once you find one that stops the PET from working, you've found the culprit..
 
Wouldn't a quick test to check if it's the ram or a rom is a config on the pet vet to use either the motherboard ram or the internal?

That would rule out the ram as the main source quickly.

Later,
dabone
 
Just a quick apology. I've been away, now back. Should be able to examine the board tomorrow, if I'm not moved again..
*sigh*
 
Yup, this would be a good way to do it. You can modify the firmware-building script to set the RAM space to 'BYPASS' or 'REPLACE', on two different jumper settings so you can switch between them easily. If I get a chance later today I can do this and put a new firmware up on the site which includes these settings.

dabone said:
Wouldn't a quick test to check if it's the ram or a rom is a config on the pet vet to use either the motherboard ram or the internal?

That would rule out the ram as the main source quickly.

Later,
dabone
Click to expand...
 
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