As far as I can tell there's a subroutine call at address $E5B7 during boot. The chirp routine itself is located at $E6A7, generates only one chirp, so it's called multiple times during a successful boot. Once Basic was started normally you can call the chirping routine manually by typing the sys590...

As I know b* is displayed when program execution is aborted by a "brk" instruction (software interrupt). RAM space between $0400 and $8000 is the Basic program area. If garbage is present at $0400-$0401 (e.g. due to a faulty RAM chip, or due to noise on the data bus) while the Basic is ini...

Well, if the machine is equipped with Basic 4.0, the address $c5b0 should be the entry point of a string processing routine. The data you've provided can't be interpreted as a working ML routine, it contains invalid instruction codes, and break instructions, preventing the machine from boot. Even if...

Hello, and welcome to the forum ! Congratulations for the machine, I think it's a rare piece. For a start, when the boot sequence ends up in the ML monitor, you can try to enter the following command: m c5b0,c5b9 mem_dump.jpg Compare the actual numbers with the ones in the screenshot. If difference ...

Hi, When the machine stops working it may worth to check the +5V supply on the user port edge connector pins, while the power switch is still on. (1st and 2nd pin from the left at the top side of the edge connector, 1st is the ground, 2nd is the +5V supply) If the voltage is below 4.8V that may sugg...

Something went wrong with the link, here's another one:
http://1541ultimate.net/content/index.p ... Itemid=127

It seems the port lines of CIA2 won't be won't be emulated, since the user port was replaced with modern interfaces.

Hi Robert,

Is there any blog entry or website (or maybe a video) with further details regarding this modification?

Hi, VICE can emulate many different PET machines, and they are different in terms of screen (40 vs 80 column display) and memory layouts. You can see which PET type is currently emulated by checking the "PET model settings..." from the Settings menu (see the attached screenshot). A program...

Hi,

Component IDs starting with "Y" are usually referring to crystals.
In case of 8096 MB "Y1" is a 16.000 MHz crystal.

But the real question remains: what caused it?

Hi All, A year has passed since the last post, so I thought it's time to update the topic... Thanks to Robert I've contacted Steve, and we've exchanged a few e-mails in December of 2015 and January of 2016. He created a cycle accurate code to achieve 38.4kbps. In my last post I've mentioned the scre...

Update: Although the 6529B IC is capable to read from the port, it seems this mode is not implemented in the Plus/4. Only the write/output mode works. I've opened up my Plus/4 to check the CS and R/W lines of the port IC: Plus4_opened_up.JPG The 7700 PLA enables the 6529B port IC by lowering the it'...

Yesterday evening I've dug out my old Plus/4 and a wiring diagram for it. The user port is shared between a hardware serial port (unlike the C64 which has software emulated one), and an 8 bit parallel port. The serial section (capable to 19.2 kbps) is well documented, so I think I can't add anything...

It's been awhile since the last update, but finally I can present some results. I've searched to Agent Friday's work mentioned by gsteemso, but no luck unfortunately. After testing the built-in RS-232 send routine, it's became clear that there are port timing issues present above 300bps speed, there...

Hi,

For me Shift and "-" (minus) and Shift and "+" keys (the two adjacent keys to the backspace key) are bringing up the opening and closing braces in the editor:
(without any additional keypresses, I've tried it on a notebook and a PC keyboard as well)

Hmmmmm, Have you tried the commodore schematic? 6526 CIA... Hmmm, how to get that puppy moving??? Hi, yes I did it actually. We got two puppies, and the focus is now on the second one. The 2Mhz version of the 6526 would accept max bit rates of 500Kb/Sec.... Well yes, but since the C64s and lot of C...