And here I was upset that my SBCs were 1s apart after a month!

My work laptop loses 4 minutes over a 2 day weekend.

I should clarify, I do not have a RTC in my system. What I meant each time i said RTC is TOD clock.

Doesn't excuse the fact that my ISR is miles long to handle all of the BCD and regular binary math.

I keep my Jiffy counter in zero page for sure, but the 4 byte uptime counter and also my RTC clock which is BCD seem to do fine in regular memory.

Only the Jiffy counter is touched on every Interupt. the lowest byte of the uptime counter is touched once per second, as is the seconds byte of the ...

By any chance does anything in your ISR write to the stack?

Do you have an NMI triggering during a regular interrupt?

Shotgunning ideas based on mistakes I made on my machine.

Add 17 million plus for the 6502 tamagotchi, one of many toys mentioned above.

If anyone missed it, the 6502 source code from the tamagotchi is available for download

Edit: make that 82 million as of 2017, I can't copy-paste effectively.

Borrowed a frequency counter, just to see...

The original oscillator I was using comes out at 3,999,940+-20 Hz.. max error of 15PPM is pretty acceptable.

The "questionable" Chinese oscillator has never been lower than 3,999,980 and usually hangs out in the 3,999,998 range, depending on room temp ...

I have a Mensch Microcomputer (the $18 board) if you need anything from it. I remember the slow/fast clock switching worked just fine.

I haven't done much with it past hooking up the serial port and booting it.

From Mapping the C64 ...


Bit 0: LORAM signal. Selects ROM or RAM at 40960 ($A000). 1=BASIC, 0=RAM
Bit 1: HIRAM signal. Selects ROM or RAM at 57344 ($E000). 1=Kernal, 0=RAM
Bit 2: CHAREN signal. Selects character ROM or I/O devices. 1=I/O, 0=ROM
Bit 3: Cassette Data Output line.
Bit 4 ...

You can translate the code to use another assembler you prefer.

Most of the work can be done with simple text replacements.

I have converted this same code to work with the ACME cross assembler for my project.

now about those errors. they are with the code shown above and i don't understand why.
C:\Users\N\Desktop\EhBasic222p5C02>WDC02AS -g -l -DUSING_02 basic.asm
WDC 65C02 Assembler Version 3.49.1 Feb 6 2006 17:25:36
Copyright (C) 1992-2006 by The Western Design Center, Inc.
RTS
^
Pass 1:File basic ...

semi-related observation of the weekend.

My Rockwell R6522 (maybe china relabel?) which is supposed to be a 1-2mHz part works great at 3.3mHz. At 4Mhz the ports don't respond to input/output in any way, but the timer still works.
In fact, it's successfully creating an NMI tick at 8 and 10Mhz clock ...

To my amateur eyes, that screen looks correct for drawing a blank screen.

Time to check the computer side of things, is the clock working, is the CPU stuck in reset, do the address/data lines look good, that type of thing.

The main board bodge wires look like factory fixes, or are VERY well done ...

My uptimes aren't nearly as impressive. My machine sits in a BASIC loop redrawing Mandelbrot sets in different colors.

My not nearly as impressive or informative Youtube video.
https://www.youtube.com/watch?v=5WBXG1EIiCY

If I didn't have two displays side by side, I wouldn't have noticed.

1 minute fast over 3-4 months? Close enough!

Found a data sheet for what it's labelled as. I of course don't trust the label at all, but the datasheet calls it a +- 0.1% part, so no surprise that the time keeping isn't very accurate!

I have a 5 pack of these, some day I will put a them on a frequency counter and see just how far off nominal ...