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Hello all

Im a retrogamer and have accumulated a few systems over the years. I've got a couple of dragons and have recently dusted them off, built a video cable and joystick, and got some software running on one of them.

One's poorly (I suspect a RAM chip) anyone know if theres any diagnostic programs out there? it will boot up and load programs but attempting to run one results in a screen of garbage. Ruled out the software and psu by testing on the working dragon. Voltage supply from the power board to mainboard is spot on.

I know 4116 RAMS are prone to fail from working on williams arcade PCBs (joust & defender are two i own) i have spare rams but theres nothing to indicate the fault - if it is indeed ram.

cheers, hope to be able to contribute to the forums - i may get the probe and scope out and see where that gets me.

Hello and welcome,

Programmers Utilities by Microdeal includes a RAM test program. The downloads section of the archive has a cas file but I will also include the wav file of just the RAM test program here. I hope this is of some help.

** triple post due to lost in moderation

*** triple post due to lost in moderation

Thanks for that. Sick dragon wouldn't even load it. (Worked fine on other dragon).

Weird thing is it has loaded basic programs that were bigger than the ram test.

It would also load the hunchback title screen, presumably thats just being fed to video RAM;



had a good play with the well dragon, donkey king is hard as nails

I was going to suggest that you load the RAMTEST program at another location, since you might hit exactly the bad RAM when you load it, and the BASIC programs you have tried might load somewhere else. But then I tested it myself in xroar and saw that it was not relocatable.

Since I also was curious to how it tests the RAM, I disassembled the program completely. In fact the program is not overly sophisticated. The RAM test itself will for every byte write one bit and shift this bit through all 8 bits, reading back for control at each step.

Then I converted the program to position-independent code, so that it can be loaded and run from any RAM location. So please try the ramtest.wav in the attached zip file (which also includes the source codes). The RAMTEST 30 years anniversary edition

From the included README file:

The RAMTEST program checks the whole RAM except the location
of its own code. Run it twice from different locations in
order to check all RAM. The code is only ~400 bytes long, so
the offsets must only differ by this amount to cover the whole
RAM.

The code can be loaded at different location using the offset
parameter of CLOADM. For instance, to load and run from address
1536 (graphics memory page 1) and 2560 (one 1K away):
Note that an offset is always needed! The default loading address
of the file is set to 0 for simplicity, and this address can not
be used since it will clobber the BASIC system variables.

To load it somewhere completely safe from BASIC, reserve space
above BASIC using the CLEAR command, and load it there:

Grobda, in addition to Tormod's modified RAM test, what happens when you type in, LIST, then run the following program (keep pressing any key until the program ends) on your faulty Dragon? If any of this fails, where does it fail?

Is PRINT MEM returning the usual 24871 bytes free?