On Sat, 3 Nov 2012, Steve Nickolas wrote:
The point is that if there's a long IC on the board besides the 6502, then it's very likely a Z80.On Sat, 3 Nov 2012, David Schmidt wrote:On 11/3/2012 6:34 PM, Sam Latella wrote:David Schmidt wrote:On 11/3/2012 4:47 PM, Sam Latella wrote:Thanks for info... It looks like this one has 7 slots and slot 0 holds a strange ROM board.The ROM board was a way to decouple the bootleg ROM from the main board - a way of circumventing the looming trademark wars for a time.What do you mean by Z80? The Z80 card itself? Or is that the 80 column card?One style of clone board had a Z80 chip (the workings of the Z80 card) embedded right on the motherboard. They could offer built-in CP/M compatibility that way.Cool... I'll have to check if this clone has it built in... I guess I wouldtest this by running some CP/M software on it right?That's one way. Or just look on the board for a big long chip with a Zilog or Z80 marking on it...Goldstar Z80s (Korean clone - the company's now known as LG) don't say Z80 anywhere on them. I don't think NEC or Sharp Z80s do either.
I found one of those boards once, and the IC was missing. INitially I was puzzled, why would there be another large IC on the board, then I must have traced things out enough to realize it was for the Z80. On one level, it makes sense, a lot of Z80 boards were sold so why not toss that in, yet I sure would have thought an 80 column circuit on the motherboard would be of more immediate value. But maybe it was more a question of fitting things in.
By definition nobody would want to fiddle too much with the circuity since it would become non-standard. A Z80 was a way to offer a premium, something to distinguish itself from all the other clones, without making it non-standard. One time someone gave me a clone that had a serial keyboard. That was interesting. It used a "standard" IBM PC keyboard, but the ROM was changed so it would output ASCII rather than the odd code that the IBM does (which is one code for keydown, another for keyup), and then a small board plugged in where the keyboard would normally plug into, it was just a small ttl serial to parallel converter, to get the serial output from the keyboard into the parallel that the motherboard needed. It was a neat trick, since if you unplugged the tiny serial board, you coudl plug in a standard Apple II keyboard, yet by this simple addition, they could make the keybard separate from the box with the motherboard. When I was given it, I was handed the original ROM, so the keyboard could go back to being used with an IBM PC.
Michael