e p chandler wrote:
On Oct 19, 3:03 pm, "Michael J. Mahon" <mjma...@aol.com> wrote:rhohler wrote:The NuMustang discussion got me thinking. What is the rarest Apple II card today? Of course, prototype cards are limited and rare but what production card. I would bet on the Transwarp II card or something.I have some 128K bubble memory cards that emulate a Disk ][ with somewhat less capacity. They were made by Helix Labs, and were intended to provide non-volatile storage for Apple II's used in harsh industrial environments.I once considered using one of these in a project which buffered data from a multi-channel analyzer. The problem with the disk 2 is that it disables interrupts ([perhaps it was DOS 3.3....) The commercial solution to the problem used a clock card which itself generated interrupts. My idea was to write the data to bubble memory instead of to disk.
It is a fundamental requirement of the Disk ][ controller that no interruptions occur during reading or writing. Both are timing- critical operations--the 6502 is running as a real-time disk controller. I'm not sure whether the bubble memory cards have any real-time requirements or not... It depends on whether or not the supporting chips control the bubble shifting asynchronously.
As far as rare cards go, I did see a demo at a club meeting of an modem card that had a number of special abilities (no I don't live in silicon valley). It was never produced because it had a tone generator built in which would have turned the Apple into a blue box (yes I know the guys at MIT did it first!).
Wasn't that card made to Captain Crunch's specifications? ;-) -michael NadaNet and AppleCrate II: parallel computing for Apple II computers! Home page: http://home.comcast.net/~mjmahon "The wastebasket is our most important design tool--and it's seriously underused."