I've been searching, and have tried several. No joy at all.
Any suggestions?

Thanks, BigEd for the help. rfpowerdude has contacted me and are again in touch.

Floobydust,
I'm the author of SyMon. I am thrilled that you tried my code, more still that you are reworking it! I'd be very interested to have a look at your mods. Just curious and mebbe give your version a try.
Best Regards,
Brian M. Phelps

Yes. I love the look...all those colorful pin jacks...the modularity...truely
a piece of art. I sure wish I could take a CLOSER look at the nitty-gritty
internal details, though. Good find, twh1st.

Brian M Phelps

Hello All,

Interesting idea indeed.
Assuming a systen already set-up for DMA access and already using
interleaved memory access (video controller?) this has potential to
eke-out a bit more bandwidth for (almost) free. Check me on this:
DMA access throughput (during dead cycles) will be mostly ...

AHA!
Found the problem: a faulty crystal.
I tried the cap/res across xtal idea, it didn't help.
I found a few 1.8432MHz xtals in my junque box, and they all worked
just fine, with or without the caps.
I opened the "can" of the suspect and found the conductive coatings
on the quartz were damaged by ...

1.8432 MHz crystal and a 10 pf cap (in parallel with each other)
Hmmm. I don't think I tried that. I had a cap from each side of the xtal
to ground, tried with one cap, no caps, different value caps, etc.
In some cases, the osc would start if I "pinged" it after power-up.
If indeed a cap ACROSS ...

Howdy everyone,

Have any of you been able to get the NMOS 6551 part to work
reliably (or at all) using a crystal rather than an ext. oscillator?
The CMOS parts that I've tested all work OK with just a xtal and
a couple of 10-20pF caps. According to the Rockwell data sheet,
the NMOS part should work ...

<more>
You mentioned this:
I then disconnected the wires to the other chips and with the 6502 alone the same condition persisted.
That is to be expected, especially when using the NMOS parts (see my last post).
Operation of the 6502 with nothing tied to its data bus will result in utterly ...

I have to ask, um, what's in your EPROM?

If it's a brand-new one(doubtful) or if it has been erased,
it'll be filled with $FF.
For the 65C02, $FF is a valid opcode. This situation
would, on RESET, begin executing code at addr. $FFFF.
The instruction would then be: BBS7 $nn $nn, where
nn is whatever ...

How about the 8255/82C55/D71055C(fast) parts,
which are dirt cheap?
One write configures all ports, and inputs may be
later coded as outputs etc. as needed (not so using
latches).
The 82C55 is available in surface-mount; don't
know about 8255 nor 71055.

Just some thoughts...

Brian

Howdy everyone,

Until the past few days, I had never played a game of chess. :oops:

Nevertheless, I wanted to check out Daryl Rictor's modified version of Peter Jennings' MicroChess.
Needing a DOS run assembler, I downloaded TASM 3.01 from Speech Technology (see bottom of the page).

I had to ...

This is a circuit I use to save board space.
It uses the MAX233 IC as both RS-232 interface
and power-up system reset timer.
Here's a JPEG schematic.
This should work with the MAX232 as well (with appropriate
pinout adjustments...)
The 1N4148 diode dumps the capacitor on loss of Vcc. The 100 ohm ...

Just a minor detail, but the board you've shown is from an Apple ///, the succesor to the Apple ][. Both were based on the 6502 chip. The Apple Lisa was a much more powerful machine based on the 68000 chip...

Yes. 'Seems I was confused about which project was called LISA...
(by the way...yes ...

Years ago, a friend showed up at my place with an APPLE][[ ("LISA").
While it would light, it reported some kind of malfunction (don't
remember which). He took it with him when he left, and I figured he'd
try to fix it....

The following week he again showed up, this time with only a RAM
board. He ...