Blog · corpus.blog/blogs/michaeldoornbos.com/posts
michaeldoornbos.com
michaeldoornbos.com
2021
17 Jul 2021
It’s MiniPET 40/80 day. The first 10 are numbered and I have number 3! Pretty neat. These switches are gonna take quite a while to assemble and solder. As usual, fantastic packaging by @futurewas8bit I’ve been looking forward to assembling this for quite a while. #commodoreoriginal ↗
16 Jul 2021
Just trying out my dual video capture. Might as well have a couple of them race. Atari 400 vs VIC-20 same program. Curious that the Atari has the same processor clocked higher but is slower in this version of BASIC. It sure was harder to type on versus the VIC. #commodore #Atarioriginal ↗
15 Jul 2021
SVideo out on the Atari 400. Have to hold the cartridge port switch down when it’s out of the case to get it to boot but it’s working. #atarioriginal ↗
14 Jul 2021
10 minute lunchbreak progress: Porting an old PET maze routine to the VIC-20 and Atari 400 for a project (also just for science).original ↗
12 Jul 2021
VickyTwenty ended up being two things: The unsoldered pin on the character rom that was only making contact sometimes, and it turns out that the socket under the VIC was cracked. Not in love with these precision sockets, many chips fit loose. May have to change brandsoriginal ↗
11 Jul 2021
11 Jul 2021
Troubleshooting a VIC-20 with a strange color memory issue. Is working other than this. I've swapped all 5 RAM chips.original ↗
11 Jul 2021
This is the first "real" video out of my VickyTwenty. I used a video mod board to get S-Video out on it.original ↗
9 Jul 2021
Parts order from retro8bitshop came today for my 250407 replica. I may start this one next depending on if/when the MiniPET 40/80 ever ships.original ↗
8 Jul 2021
Finally getting to the Romulator in a little bit. I'm thinking a VIC-20 will be the target for it tonight for first testsoriginal ↗
7 Jul 2021
Helping some students with math contests and they're having trouble visualizing cellular automation (Rule 30 in this case). Doing it nice and slow with a color change on the row being worked on was the trick. Old computers are still valuable teaching toolsoriginal ↗
5 Jul 2021
5 Jul 2021
I almost never get landing shots because... well kinda busy. It's nice when someone is sitting in front and takes them for me ;-)original ↗
2 Jul 2021
I love that someone else is hacking the CERBERUS 2080 bios. Working on some hacks to mine already. Too funoriginal ↗
1 Jul 2021
Definitely my strangest flight path to date. Had us doing circles for weather for about 45 minutesoriginal ↗
1 Jul 2021
Hey it even works. I’ve got a bad 6522 so I ordered those WD “modern” replacements. It boots to a cart just fine without the one so I suspect that’s the whole of the problem. If not, VIC-20s are a joy to troubleshoot. My third favorite computer of all time.original ↗
30 Jun 2021
The Mechboard64 ended up in the Ultimate after much deliberation on my part. It's rock solid and I'm very happy with it. The keyboard it replaced is in good shape and will live on in the VickyTwenty.original ↗
28 Jun 2021
Actually getting back on track with ciphers on the C64 this evening, but during my lunch I just wanted to make sure I could do a 3 line assembly program on the CERBERUS. Easy enough, but the removing SD card every time to make changes is gonna get old. Time to extend this thing!original ↗
28 Jun 2021
27 Jun 2021
Since I'm waiting on 4 components that weigh a total of about .1 ounce for the Cerberus, I figure my lunch break can be used to make progress on one of my other 12 million boards to build. VickyTwenty, you're nextoriginal ↗
25 Jun 2021
Who wants an old computer that looks new? Pre distressed jeans are a thing right? So starting next week I’ll be offering a product called “retro yellow”. I think it’ll be HUGE!!original ↗
22 Jun 2021
Today on “dumb calculator races vs the VIC-20 I changed this to repeat 10 times for better comparison. A PAL VIC20 beats the TI-81 (z80 running at 2Mhz) by about 10%. A screen blanked NTSC C64 (POKE53265,PEEK(53265)AND239) is neck and neck with the calculator. #commodoreoriginal ↗
22 Jun 2021
The mystery of the VIC-42 chip is much less interesting than I hoped. I happen to have an Alphacom VP42 printer. It has the chip in itoriginal ↗
22 Jun 2021
This week on “dumb calculator races vs the VIC-20” we add the TI-81. Its z80 processor is a much more formidable opponent than the Sharp 9300 from the same period.original ↗
21 Jun 2021
Evening CERBERUS progress. Got all 56 10k Resistors done. I'll wrap up the soldering tomorrow with the taller components with the exception of a transistor I had to order. Still might be working by the weekend if I don't screw anything up.original ↗
21 Jun 2021
And in other news, I bought a working working Plus/4. For now. I've doomed it by posting it here.original ↗
21 Jun 2021
Lunchtime project... Composite video mod on my Coco2. I didn't even blow it up or anything. Haven't used this in many many years, the green is just as horrible as I remember ;-)original ↗
21 Jun 2021
I started flying too late to have been required to use one of these. Modern equivalents are much faster, but I did learn how to use it. I love the big picture understanding of how things work in relationship with each other that only analog tools can reveal.original ↗
20 Jun 2021
Morning progress. Couple hundred pins soldered. Not hard, but the pads are tiny so it requires some patience. All of the sockets are done.original ↗
19 Jun 2021
As some have pointed out, the print routines are probably VERY slow on the calculator. I took them out and made the VIC code the same as what's on the calculator as close as I could. VIC-20 is still faster. Pretty fun. Next up, head to head with TI-81original ↗
17 Jun 2021
What do you do when you have a bunch of 25-35 year old calculators than can run BASIC? I know what I'd do, I'd race them with a 40 year old computer. They have pretty similar RAM, but the VIC-20 beats a Sharp 9300c from 1991 easily #commodoreoriginal ↗
16 Jun 2021
My morning routine is to work out and then spend 15 minutes learning something new. This morning it's @TechTinkering 's tutorial on using screen memory as extra storage to do the 100 door problem on unexpanded VIC-20s. Good stuff.original ↗
16 Jun 2021
The 250407 Replica by @bwack77 arrived today. It's amazing. I now have a trifecta AND the MiniPET 40/80 hasn't even shipped yet. This is gonna be A LOT of soldering...original ↗
15 Jun 2021
When you put VIC-20 CR machines back together, you have to keep the bottom RF shield because it helps with mounting. They are always terribly rusty so I paint them. Apparently my paint supplies are low and I have... white. No one is gonna see it anyway so white it is.original ↗
14 Jun 2021
I’m not huge on multi tasking, but recapping a board during a conference call worked for my brain.original ↗
14 Jun 2021
Oh yeah! VIC cipher decryption on an unexpanded VIC-20 is finally working! This was a lot harder than the encryption part. Now we work on cracking itoriginal ↗
13 Jun 2021
Well I have one of these mystery VIC-42 chips and it doesn't test "good" as a VIC or VICII on the backbit. I think this might be something we just have to make up a story about. "There I was, wire tying a Commodore 264, when I was attacked by a Spectrum…"original ↗
13 Jun 2021
Mechboard64 is almost done. Need to print the key cap adapters and bend some piano wire. #commodoreoriginal ↗
13 Jun 2021
I was an AT in the Navy which required extensive color blindness testing. But these things are practically impossible…original ↗
12 Jun 2021
Testing a new video capture device on the VIC-20s. Only one of them is good enough to probably be post-able. Something to work onoriginal ↗
11 Jun 2021
11 Jun 2021
Going easy on myself with the next in the crypto series since I wanted to do a couple of these on the VIC-20 in Assembly which is new for me. Fibonacci in was simple enough. Now to do a Lagged Fibonacci.original ↗
8 Jun 2021
10 Second review of this drop in RAM replacement for your 128: Works like a charm. If your RAM is already socketed installation is 4 seconds. One more future proofed item in the bag.original ↗
7 Jun 2021
Interesting, removing this resistor and adding a 220uF cap across these two lines DRAMATICALLY improved this PAL VIC-20's picture. It's hard to tell from a photo of a screen, but this looks excellent IRL. Not 100% sure why this works...original ↗
4 Jun 2021
10 minute lunch break progress: I think I’ve found a VIC 20 Assembler that fits my brain. Flashing screen warning.original ↗
3 Jun 2021
More than one person gave me a hard time about using Monte Carlo to test my PRNG without a visual. Okay, here’s a squished PAL VIC circle and point plot of it :)original ↗
3 Jun 2021
Why are PAL VIC-20 (CR) video output circuits wired like the left and NTSC like on the right?original ↗
2 Jun 2021
Before morning workout progress: This is the last of these before the refactor to do large sets on an unexpanded VIC-20. This one cheats and uses a 128 to do 30k DIMs. #commodoreoriginal ↗
2 Jun 2021
SUPER happy with this so far. Generating 100 random mod 256 integers with a Lagged Fibonacci Sequence, then test the distribution for randomness-Monte Carlo value for pi (is it in the circle?) on an unexpanded VIC 20 #commodore #embracecontraintsoriginal ↗
1 Jun 2021
Well, that random distribution count really sucks. Gonna have to work on this algorithm a lot more… In 10000 iterations, 1 came up 358 times and 2 came up 1669 times. Bleh.original ↗
1 Jun 2021
Sometimes during conference calls I do weird things.You know, like write a Lagged Fibonacci Generator (PRNG) on a VIC 20...original ↗
1 Jun 2021
Headed out for a holiday cookout, but while I'm waiting for everyone... I need top 500, 1000,10k and 50k English word files in SEQ files. Was simple enoughoriginal ↗
31 May 2021
I’ve read a lot of marginal documentation over the years. This one is in the bottom 5 of all time. I’ve read it twice and I still don’t know how to do anything with it.original ↗
29 May 2021
Done a fair amount of Commodore Assembly now but never on the VIC 20. No time like the present. Seems simple enough but I’m going to have to find a decent editor, the monitor method only works so long.original ↗
28 May 2021
Another new to me VIC 20 “untested” and cheap. Looks good, packed well and passes tests. Sweet.original ↗
28 May 2021
Back to implementing Enigma. These rings are obviously horizontal for testing, but top down they are left, middle and right. Middle should rotate when right(bottom) gets to V (the "notch") and top when middle gets to E. Making progress...original ↗
28 May 2021
I'm doing a Pi computation demo over the weekend for some young people and want to do a couple on Vintage machines. Then I remembered that @8BitShowAndTell did one with Logo graphically. Perfect, I shall borrow (steal) Robin's demo as well.original ↗
28 May 2021
Earlier today I was annoyed when my truck’s software served me a damn ad. Then I remembered the flier in Pirates Cove from 1980. I guess this isn’t a terribly new idea. Be careful Chevy, or I’ll replace that software with a VIC 20original ↗
27 May 2021
This little bastard was causing all kinds of gremlins to intermittently appear. Crazy how much better things run if the power into the board is clean.original ↗
27 May 2021
Chased down a VIC-20 flickering screen for quite some time. Came down to this solder joint being weak. Reflowed it and all betteroriginal ↗
26 May 2021
Such a great series. I wish I had read these back then, but there’s no time like the present.original ↗
26 May 2021
Here's a fun one. Another friend brought over a 128. It started up but it was acting really strange. Probed a couple voltages and they came in at 4.1... Deoxit in the power switch and its fixed. I'm basically a wizard.original ↗
20 May 2021
Actually really busy with day job today, but had a 10 minute break and decided to put a 128 back together. I spent more than a minute scratching my head on a U4 failure message. Maybe I no fix hardware today huh? Sheeshoriginal ↗
20 May 2021
20 May 2021
My CERBERUS 2080 Boards came today from @JLCPCB and look great. A couple of these chips are backordered but I'm really looking forward to getting this working. I had to order 5...original ↗
20 May 2021
I am looking for a manual or documentation for Vickit 4+5 on the @futurewas8bit Penultimate cart. Anyone have it handy? #commodoreoriginal ↗
19 May 2021
Working on the Retro pinout project a little at a time. 128 pins captured and about 4500 to go. Thanks to all who have offered to help so far.original ↗
18 May 2021
My new open source project: Collecting scope outputs on every IC on retro computer boards. I'll need lots of help from the communityoriginal ↗
18 May 2021
I went right to getting the VIC working yesterday and am just now getting to the bucket of other stuff @TheGavNinja sent me. Lots to check out #commodoreoriginal ↗
18 May 2021
17 May 2021
Brought another vintage computer back to life from the trash bin. Some probing around with the oscilloscope narrowed it down to a bad VIC chip. Desoldered, installed a socket and replaced it and it’s back in service.original ↗
17 May 2021
The first spreadsheet I ever used was Practicalc. Seems appropriate to use it to hold a BOM for a new retro board buildoriginal ↗
17 May 2021
Just reading this book for the first time. It’s really good. Seems like a possible candidate for an @8BitShowAndTell book club.original ↗
14 May 2021
Did you know that Bruce Schneier created a cipher for Neal Stephenson in Cryptonomicon(1999)? Uses a simple deck of cards, so naturally…Commodore 64! Should actually work on most 8 bit machines of the era with slight mods.original ↗
13 May 2021
I guess I shouldn't be surprised, but 3583 bytes on an unexpanded VIC-20 really isn't much. My Pontifex program doesn't fit ;-)original ↗
12 May 2021
I guess I shouldn't be surprised, but 3583 bytes on an unexpanded VIC-20 really isn't much. My Pontifex program doesn't fit ;-)original ↗
12 May 2021
Retro computer repair people problems… when you need an NTSC VIC and TWO PAL versions arrive firstoriginal ↗
12 May 2021
12 May 2021