Anthony Ortiz wrote:
> > The code from UCSD BIOS can run
> Pardon my ignorance, what is UCSD? Link?
Sorry, UCSD-p-System, often called "Pascal".
> >When modifying this BIOS I wanted to add a keyboad driver which is
> triggered by a timer (6522). But you need an additional timer chip.
> I would imagine that even if you did do this it would still need to poll
>the keyboard strobe for key presses periodically and I presume send an
Yes, this is independant from CPU frequency. An interrupt every 50msec
(20Hz) seems to be sufficient.
> > Changing the mouse pointer can theoretically slow down the fast CPU to
> run the write cycles in video screen buffer on the main board. But just
> the write cycles if they are too often. This never happens with a 3.6MHz
> This last paragraph lost me. I would think there is a definite guaranteed
> slow down since, even though the mouse may trigger an interrupt, that
> interrupt needs to be processed and eventually read the x and y
> coordinates from the mouse card which slows it down to 1mhz, no?
Ok, there is a firmware ROM on the mouse card. This driver in ROM will
slow down the fast cpu to 1MHz exactly when this code is running. But
code in RAM runs at full speed, if you set the DIP switch to fast (OPEN
#7 in block 2, means the right DIP switch, if your mouse card is in slot
#7). And that's what I meant: the code which moves the mouse pointer on
the screen is typically located in the language card and is running at
> I also didn't understand what you meant by the write cycles, nor why the
>Transwarp would not be affected by any of this.
I assumed that it's clear that code from any ROM on a slot card is
always running at 1MHz. The code from the local RAM of the Transwarp is
always running fast except there was an access to a slot card which
forces slow execution for some msec like the disk controller code.
> In my mind I would have the Transwarp constantly poll the keyboard when
> it's not performing other IO and keep the last state ready for quick
> access; I don't know if it does that. I would also do the same for the
I expect that the driver which polls the keyboard is always part of the
operating system. This code is located in the language card, means it's
fast. If you move the mouse driver code from the slot to the RAM onto
the Transwarp this code will also be fast.