Re: A few technical q's from an apple newbie

[Moll <Bettykate@dosius.com>]

Mark McDougall wrote:

> Hi all,
>
> I'm completely new to the Apple II, having done nothing more technical 
> than play Lode Runner on any Apple II until a few days ago - and even 
> that was some 15+ years ago! ;)
>
> I recently decided to have a crack at emulating the Apple II in an FPGA, 
> just because I thought it'd be fun. FWIW here's my page with some 
> progress... see the PACE/Nanoboard page if you're interested...
> <http://members.iinet.net.au/~msmcdoug/>
>
> Anyway, over the last few days I've been researching on the net, reading 
> the FAQs and looking at the MESS apple2 driver etc but still can't find 
> a definitive answer to a couple of questions. I thought I'd try here to 
> see if any of you knew the answers off the top of your head before 
> delving deeper into emulator source etc...
>
> 1. IRQs. Does the apple have a periodic IRQ? Mess *appears* to interrupt 
> on scanline 190 every second frame but I've also seen another emulator 
> which doesn't interrupt at all. And if so, what is the pulse width of 
> the IRQ and is there an ACK? The reason I ask is that I've got the apple 
> running but there's no cursor at all. Does anyone know what drives the 
> *flashing* cursor? Is it an IRQ or a vblank, or something else?

I think it's separate logic.  It's not IRQ.

> 3. Memory. Are the jumpers that set the installed memory size purely for 
> memory decide logic, or are they something that can be read from s/w? 
> i.e. does the apple know how much memory is installed via these jumpers, 
> or does s/w have to do a memory test to find out?

I think software needs to find the memory.  I've never even tried 
emulating less than 48K.

You could also try looking at the EMU][ or Dapple sources - EMU][ very 
precisely emulates the video of the Apple ][.

> P.S. I was a TRS-80 man myself but Lode Runner *was* an awesome game!
> ;)

XDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD

Moll.