Category: Uncategorized

Commodore PET: 40K RAM with SoftROM

The Commodore PET was one of the first true PCs. The entry model PET 2001 in 1977 came with 8K of RAM. My own PET 3016 from 1979 came with 16K, which I upgraded a while ago to 32K of RAM. This lets us run a lot of software, even interactive fiction games, for example Planetfall and Zork by Infocom. However we can do better! Using the SoftROM expansion we can add an additional 8K of SRAM to our system, that can be used by the Infocom interpreter, or any other software that knows about it and is changed accordingly.

Black Amiga 500

Many a computer from the 1980s is today yellowed and brittle. The plastics age considerably over the decades. You can do some mitigation by retrobrighting with hydrogen peroxide. However for some machines you can even get replacement cases, and in some cases even brand new key caps for the keyboard. Today we will transform a beige Commodore A500 into a black beauty!

Zombie Floppy: How To Revive A Broken 1541 Head

The Commodore 1541 floppy drive is a real workhorse, that was used by millions of C64 users. It came with drive mechanisms from different vendors. The Newtronics/Mitsumi drive assembly has the annoying fault to have their drive heads fail due to some wires going open inside of the read/write head. This is so far not economically repairable. However a clever user by the nickname of Ruuudi on German Forum64 has designed a little bodge PCB to make the half of the head that is still okay to all the work and thus revive an otherwise dead drive.

PSU Battle: Commodore vs Electroware

The original power supplies of our Commodore home computers are now at least 30 years old. Many need maintenance, some got lost or are defective. There are modern replacements. But are those any good? Are they better or worse than the old supplies? In this video we will compare my original Amiga 500 supply to a modern Mean Well based PSU by Electroware. We will mostly compare the ripple that both PSUs produce, which is one of the main factors that could disrupt the functionality of a computer.

Amiga500: Lazarustorm/PiStorm vs ACA500plus

The original Amiga 500 is a great machine, but its 7MHz CPU is a bit slow at times and the 512K of base memory quite limited. We take a look at two accelerator cards that increase the CPU speed significantly and also bring a large amount of extra memory to the table. All the while these cards don’t require you to open up your A500, but instead they fit on the expansion slot on the left side of the Amiga, making the process very easy and reversible. Let’s take a look at the PiStorm based Lazarustorm and the Individual Computers’ ACA500plus.

Let’s Code MS DOS 0x28: Expanded Memory (EMS)

The original IBM PC and MS DOS could — for the most part — only access 640KB of memory. The LIM EMS standard was at first a standard for RAM expansion cards to overcome this limit. On later machines like the 286 and 386 there was either support built into the chipsets or EMS memory was emulated via drivers like EMM386. Today we learn how to utilize EMS memory to play back an animation that is too large for conventional memory.

Low-Noise 7805/7812 Drop-In Replacements

Linear voltage regulators such as the 7805 and 7812 are ubiquitous in vintage electronic equipment, and especially in home computers of the late 1970s and early 1980s. They have many advantages are very reliable. Their biggest drawback is their heat dissipation. The variants in metal TO3 packages are only available used or as new old stock. So if you want to replace them with a cooler running variant these brand new drop in replacements based on modern switching regulators might be worth a try. These particular variants have extremely low switching noise, so should be very usable in devices such as the Commodore 1541 floppy drive. So we will repair one of my broken 1541s and also fit it with the modern DR340 voltage regulator!