Bluemeanie's Retro Computing

 Thanks to the fact that I could (luckily) continue working through the past year, I haven't had much time at all to do work on the AppleIISd and people have been nagging me to support non-65C02 models as well. In fact, when working from home, I wasn't in the mood to do work on personal projects at all when I've been doing professional work in the same room on the same computer the whole day long. In a brief moment of being inspired, I managed to find a bug that's been haunting me since I introduced the new SMD board design (see my last post on the AppleIISd). The problem was that despite the manufacturers claim for having a power-up write protection, the first byte of the now soldered EEPROM would be erased frequently causing the card to stop working. My manufacturing partner and I did hundreds of On/Off switching tests, monitoring power and data lines. We didn't find anything that would lead us to a solution. I reviewed the VHDL for the CPLD over and over again an...

The IBM PS/2 Model 50 is a special computer for me, as this was the model that was used in the computer lab of my elementary school, apart from a couple of IBM XTs (or ATs, I don't remember). My unit is almost complete, with a matching 8513 12" colour monitor and a Model M "clicky" keyboard. I'm only missing the appropriate IBM mouse. It was made in 1987 and has a 286 at 10MHz, 1MB of RAM and a (today non-standard) ESDI hard disk with a whopping 20MB. The case is wonderfully engineered, everything can be disassembled without tools. It even comes with a small plastic thingy to help loosen the knobs that hold together the parts of the case. After all, the power switch makes one of the most satisfying "clunks" known to mankind! I had been on my father's Sanyo XT clone on rare occasions, but, this was probably the first computer I made some "educated" moves on. The computer class in my school was so popular that every pupil could only attend f...

I haven't posted for a very long time now, but I'm up and well during those strange days (future readers just google the year 2020 😷). The even better news is that since last year I teamed up with Jens who persuaded me to make a new batch of AppleIISD cards, as reported in my previous  post . The cards are available preassembled for 59€ excl. shipping. We are trying to get a website online where you can buy the cards. Meanwhile, you can contact me at the  Applefritter Forum . I still have not found a solution to the EEPROM problem erasing the first byte every now and then. That is why there still is a jumper to enable writing to the chip. However, this needs to be changed only when changing the card's firmware. I am very pleased with this feature as it gives the user a chance to upgrade to a newer firmware version without the need of an EPROM burner. It has been a huge help in development, too when you don't have to extract the chip every minute to burn a new vers...

I always was fascinated by computer tape drives. Ultimately by those huge open-reel systems you see spinning in about every movie scene from the 60s to the 80s that takes place in a computer centre. Having learnt about the mechanics of those monsters (vacuum columns, reel servos, etc.), they are even more amazing. I am almost absolutely sure that someday, I will have one of those things standing in my living room. For now, my late 70s Telefunken M15A professional audio recorder comes close (53kg without the matching stand), but it isn't a computer drive. Although, I planned to have it under computer control (MIDI) for some time... ✇ I recently bought a 2001 Hewlett-Packard C6364A external SCSI tape drive. Why? I can't really tell. Maybe because it was only ten bucks, and it's a computer tape drive, a very small one. DDS type backup systems were common in the 90s and early 2000s. The medium is the same form factor as a DAT tape but uses a different formula and evidently t...

I bought my first NEW hardware for any of my Apple II series computers: a 4 MB RAM card for the Apple IIgs! This tiny card, compared to my old 1.5 MB AE GS-RAM, is made by an American company called "Garret's Workshop" and is sold for only $35! This is nearly half of what the cards of competitors cost. I haven't had much time to do testing, but it worked right out of the box, although I did not expect anything else from a RAM card ;-) I was told by the guys from Garret's Workshop that they are up for some more cards, soon.

A couple of days ago, the prototypes for the new hardware version 1.2 of the AppleIISd arrived. As you may tell, I made a few changes from the original design: the CPLD and the EEPROM are now SMD components, the programming connector for the CPLD is a component-less Tag-Connect, the 3.3V converter was changed and the pullup resistors are now an array. I am quite happy with the design, but I will have to change a few things for the final version, but that is what prototypes are for! The pin header for CPLD programming will be reintroduced but not equipped next to the Tag-Connect, necessary adapters are not really cheap. The slot connector will have longer pads. The third thing I still have to figure out is the following: about every tenth time the machine is switched on, the first byte of the EEPROM gets erased and I still have not quite figured out why. I am not sure if this happens on power-up or power-down. Adding pullups on the /OE and /WE lines helped to reduce the error to ab...