Search results

There are no extra Jiffies in the hardware. It is just that the CPU is interrupted at slightly higher than 60Hz (16640 vs. 16667 cycles), and the software(!) Jiffy correction ignores one of every 623 interrupts for Jiffy counting. Thus, Jiffies (in terms of the value of the TI variable) appear...

Yes I noted that RA1 routing too :-) It is indeed very space-efficient by leaving out unnecessary bits, but that indeed makes it hard to understand. It's not like simple state bits and static logic that drives changes in your state with the next clock, you have to think in the time dimension...

I.e. now I know what that Jiffy correction is for. And I know I can safely remove it. This whole thing got triggered as I am preparing a benchmark for my MicroPET ( https://github.com/fachat/MicroPET ), and I wanted to use the Jiffies as timer.... Edit: and yes, I am going to write up an...

I see here are the real experts :-) I've been looking deeper into this and I think I understood the different signals now. So, /200LINES really triggers, as @Eudimorphodon says when the start of the next line is at 1000. Actually it only tests that the bits for $3c8 = 968 are set and ignores...

Thanks, that helps a lot. Not that I understand how the NEXT pulse input is generated, but the timing anyway. So, with 16.7ms screen duration, that is 16700 cycles, so my assumption is this is running at 16704 cycl/screen = 64us x 261 rows. But then, it would be too slow and skipping Jiffies as...

Hi there, has anyone actually ever analyzed the static (or even early dynamic PET) video timings? The ones where the video display is created by discrete hardware? I've been mulling over the schematics for the whole evening, but the use of obscure counters, JK flipflops and strange logic...

Just in case you haven't seen it, I designed and built the Micro-PET, a Commodore PET re-incarnation: https://github.com/fachat/MicroPET Commodore 2001 / 3032 / 4032 / 8032 / 8296 with options menu to select at boot Boot-menu to select different PET versions to run (BASIC1, 2, and 4) 40 col...

Here is the link to the schematics: http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/pet/8032/ if you look at the file 321448.gif (or again the direct link: http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/pet/8032/321448.gif ) Here's the part of the schematics that...

Hugo, thanks, here is a link to a YouTube video with the effect in place: https://www.youtube.com/watch?v=R_EmN1XPpc8 Here is the same but with the screen filled so you better see the distortion (embedded in a twitter post): https://twitter.com/AkBKukU/status/1249828043289268224?s=20 Here is...

Hi there, there is a discussion going on on twitter about how the killer poke works and whether it actually "kills" PETs. There's actually video footage available now! https://twitter.com/AkBKukU/status/1249828043289268224 So, I'm looking for help on this forum, on any (even anecdotical)...

Hi there, I have a broken 3040 where I find that the R/W head does not fully step to the inner tracks. It seems the head uses a pin sliding over a spiral "cam activator" to be moved back and forth, and that the pin slips over the spiral back instead of following it to the innermost tracks...

Hi there, I am looking into a comparison of on-disk formats (at the low level of GCR vs. MFM etc), and also looking into the history of the drives. Apple released their "Disk ii" in June 1978, and Commodore released their 2040 disk drive for the PET in Spring 1979, with a superior on-disk...

Hi there, after recapping the 8250 disk drive in my 8296-D I decided to give it the full cleaning job. Unfortunately the keyboard fix ended really badly. One key, the "RUN/STOP" was already missing, but three more broke from the switches. I had first thought I'd be able to fix it with parts...

Hi there, recently I repaired the leaking caps in my 8250LP. When testing the drive, I found one drive ok, but the other had a high error rate on the second side. (I always get errors on the second side when formatting a disk, and I get them rather quickly - while the same disk is formatted...

Hi there, just in case you haven't heard already - it seems the 1001/8250 Matsushita disk drives in the SFD1001, 8250LP and 8296-D suffer from leaking electrolytic caps. Here is an (unfortunately German) repair instruction with pictures...

Hi there, just wanted to point you to an ongoing repair story for my B720, documented here: https://www.flickr.com/photos/afachat/sets/72157647798386959/ The current state is that it boots, but does hang on using the IEEE488 port. The next step will be checking the TPI and CIA, so I can load...

Hi there, I just wanted to share my 10MHz demo on a 9" PET4032, using my WDC65816 accelerator card. https://www.youtube.com/watch?v=ar45QJisxSg&feature=plcp Have fun! André

Hi, I have developed a new firmware for the xs1541 device. My "xd2031" plays an IEEE488 disk drive to the PET and allows to read files from the PC via serial-over-USB and a PC (currently Linux) host component. I have even already read files directly from the internet this way :-) It's...

Hi there, I was looking for a BASIC4 DOS wedge for the PET. But when looking for it, I did not really find any PET software (except what's on zimmers.net, which seems to miss some updates also). Is there a PET software repository with all the software? If not, should we create one? For example...

I've finally managed to get the PET on the "internet" - well sort of :-) At least it talks TCP/IP over ethernet now. See http://www.flickr.com/photos/afachat/5350096696/ Updates soon on my website http://www.6502.org/users/andre/index.html Cheers, André