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I cannot seem to find any homebrew memory board upgrades for the Tandy 1000 EX or HX that include the DMA function. DMA is typically required for DRAM refresh, but SRAM does not need periodic refresh and all homebrew upgrades use SRAM. DMA is also typically used for floppy disk drive data...

Pool of Radiance was originally developed for the Commodore 64 and released in 1988 for the Commodore 64 and DOS. Pool of Radiance has theme music in the C64 version which plays on the title screen and was composed by Dave Warhol (Warhol Theme). The Warhol Theme was reused for the game's...

I was gifted a TRS-80 Model 1 with Level II BASIC and 16KiB of RAM on Thursday. It came with the Video Display (no tint, B&W) and its Power Supply and bunch of manuals and a pair of cassette packages. The system works perfectly, is in excellent shape and has a nice Alps keyboard with all good...

The Amstrad PC-20 seems to be one of, if not the rarest, of the Amstrad IBM PC compatible machines. The wedge-form factor computer was released as the Sinclair PC-200 in the U.K. but as the Amstrad PC-20 in the US and apparently other parts of the world. I have seen photographs with the...

From what I have read and researched, most Apple II applications which could send output to a printer were not, at least by the time of the //e, especially particular about whether your printer connected via a serial port or a parallel port. This assumes of course that you had the de-facto...

I bought a "working" Disk II off eBay, but I have had nothing but problems with it. At first it would sometimes copy disks and sometimes fail. I cleaned the read/write head with alcohol, I lubed the drive rails with silicone grease and I reseated all the chips and cables. But now when the...

I understand that the original Apple II's boot process evolved over board revisions and the expansion cards placed in the system. Here is my understanding, is there anything incorrect here? In the Apple II with the rev. 0 mainboard, when you hit the power switch the Power bulb would light up...

One of the few things I dislike about the keyboards for the Apple //e is their arrow key arrangement. It goes left, right up, down. It is probably because I grew up with a PC and its Inverted-T arrangement that I dislike the Apple //e (and //c and //gs) arrangement. You can easily use a...

The Tandy Color Computer 3 received official releases of King's Quest III and Leisure Suit Larry, and they look and run almost identically to their IBM PC counterparts. Because the CoCo series only have a 6-bit DAC, the music output from a CoCo is PC-speaker quality on the official ports...

I have decided to part with one of the rarest of my sound cards : https://www.ebay.com/itm/303696307456

Most games that are "Apple IIe aware" use the cursor keys for movement. Interestingly, the Apple IIe has a numeric keypad connector which provides the X/Y output/input lines for a keypad. This allows you to use any passive keyboard matrix as a keypad. The numeric keypad connector does not...

I have a physical copy of this book/binder. A friend of mine was looking for it but there was no scan of it available online, so I decided to scan it and upload it. Even though the scanner was automatic and the positioning of the text and images may be a bit crooked, it is still serviceable in...

Several years ago, I found a way to display images from standard file formats on even the most humble hardware : https://nerdlypleasures.blogspot.com/2016/01/displaying-dosbox-screenshots-on-real.html But I found that the solution for CGA cards was rather limited (and slow). Of all the...

My IBM EGA card, fully upgraded to 256KB, has an issue with Commander Keen's later graphics engine. The issue is randomly wrong-colored pixels appearing in the main game. These pixels can be "corrected" in many places by scrolling the so that they are no longer visible on the screen and then...

A long time ago I acquired the manual for the AST Xformer 286 Motherboard and Setup Disk. Recently I scanned the manual and dumped the disk image. I have linked that manual and disk image here for the benefit of the community ...

There are a few systems that use 8088s and 8086s in the PLCC form factor which could be upgraded to NEC V20s (uPD70108 and NEC V30s (uPD70116). I cannot seem to find any chips in that form factor for sale unlike the DIP packaged chips, which are readily available. Other than harvesting them...

I know the Enhanced and Platinum Apple IIe and all Apple //c computers came with the 65C02 processor. The 65C02 adds new instructions, fixes bugs and eliminates unofficial and undefined instructions. However, there are Apple II programs that rely on those bugs or undefined instructions to...

All my Tandy 1000s have a DMA chip built in which cannot be disabled. I have never experienced a DMA-less Tandy, which are the 1000/A/HD/EX/HX. I would like to know if there are any differences between a DMA and a DMA-less system. The Tandy was derived from the PCjr., which eliminated the...

I know that the unexpanded IBM PC Convertible isn't any marvel of CGA compatibility. However, you can install the optional CRT Display Adapter for connecting to a CGA monitor or composite color monitor. The technical reference indicates that the Display Adapter offers full CGA compatibility...

I have a Tandy 1400 LT laptop with a pair of non-functioning keys. I would like to try to replace them, but I have never seen the switches before. Anyone have a broken or parts only 1400 LT, HD or FD? I only need the keyboard, which can be separated from the rest of the system.