New QuadLink Software Supporting Faster Turbo PC/XT Computers

[george]

Here is the first realease of QuadLink cards oftware that runs on different PC/XT computers regardless of their speed. So fa, tested up to 14 MHz on 8088 and V20 CPUs. The original 4.77 MHz clock is also supported. This is based on the latest QuadLink 3.0 software.

The original software works fine on 4.77 MHz different XTs including those with V20 CPUs. I had no 8086/V30 machine to test with though.

The original QuadLink software works fine regardless of BIOS brand and DOS version, I used it mainly under MS-DOS 6.22 with different PC/XT BIOSes.

For the 360K floppy drives I found the QuadLink hardware to be picky, probably due to its strange DISK II controller, which is not based on Woz' state machine. Many drives that work fine as PC drives have problems to read external Apple II disk tracks, and past track 9 or so work fine. It is neither alignment, nor rpm issue. Don't have statistics on a specific models yet. The question has been asked about this in another forum, nobody replied to date.
Some models of PC 360K drives accept fine diskette flipping, e.g. they are not puzzled by the absense of the index hole.
The QuadLink software works well with MDA/CGA/EGA/VGA cards, in case of VGA you should have separate monitors for the Apple ][ and PC software, not displaying simultaneously. If you have a VGA card with an additional configured as operational DB9F TTL RGB output connector, that works fine via QuadLink passtrough. If you are using a composite monitor for the Apple ][ video then note the absence of the NTCS color encoding of the composite video signal provided by the QuadLink board.

Out of many different floppy controllers I tested with QuadLink software only one with UM8397 was incompatible.

Please note currently AT computers are not supported, though no software checks to prevent the software to run on ATs exist.

 

[george]

Sadly the forum is configured not to allow editing of the initial message. Here is the the new version 1.1 of the Turbo QuadLink software now supporting PC/AT computers too. In fact it is designed now not to be limited by the CPU speed. Tested from XT computer to Athlon 1 GHz. Presently I have no faster ISA motherboards. I found out that the web sites that claim to provide information on these boards provide an outdated version of the Filer diskette. The one that came with my original Quadlink among other things has the QuadCopy utility that allows file transfers between PC and Apple2 disks. I am including the image of that diskette in the archive too.

Some motherboards, especially the baby-size 386SX ones, provide low quality 14M clock signal on the ISA bus that leads to instability of the Quadlink. The best solution is to provide a local clock. Nowadays unlike in 1983 the 14.318 MHz oscillators are (still) easy to find. The pin 1 of U7 IC has to be disconnected (put out of the socket) and a clock signal should be fed to the pin of U7. Please, don't modify the original Quadlinks, they seem to be rare enough. I bought mine recently on a local aftermarked for less than 70 EUR (on ebay they cost several times more) and thanks to that you now have software intended to be compatible with all ISA PCs, and properly cloned U33 PAL chips. Later I built a Quadlink clone for hardware experiments in a matter of hours (thanks to Plamen, who generously gave away one of his already made bare PCBs, and to the German guy who did the main routine tedious job to copy the schematics/PCB several years ago), the most that irritated me when looking at that clone PCB were the awful silly silksreen titles on the clone PCB that probably should have been written with humor, but the result was absolutely opposite.

All original Quadlink software functionality is left untouched, do you like its keyboard mapping? I found there is some design flow with Quadlink that repeatedly affects at one and the same specific places the music in Karateka. Expecting apple2 experts to shed light on this.

 

[george]

I was curious how Quadlink scales the apple2 screen when using an MDA / Hercules monitor. Recently I made a test, here are some pictures...The vintage CRT's phosphor is a bit worn out, disregard that, please. Wondering will there be an interest and usefulness nowadays if a Quadlink software version is made to supports additionally the Disk II halftracks on 720K/1.2M (96 TPI) PC drives, or on 360K drives that are jumper configurable to step at 96 TPI?