Re: How do I add firmware to a card?

[dempson@actrix.gen.nz (David Empson)]

<heuser.marcus@freenet.de> wrote:

> RedskullDC schrieb:
> > "David Empson" <dempson@actrix.gen.nz> wrote in message
> > 1hsc1jh.1hqbl6aapwbr5N%dempson@actrix.gen.nz">news:1hsc1jh.1hqbl6aapwbr5N%dempson@actrix.gen.nz...
> >
> > > I don't recall whether the 65C02 in the UniDisk 3.5 runs at a higher
> > > clock speed than the Apple II: if data is transferred between the
> > > UniDisk CPU and the 3.5" drive mechanism under processor control then it
> > > would need to run at about 2 MHz (or faster) to be able to keep up with
> > > the data rate (16 microseconds per byte, which is twice as fast as a
> > > 5.25" drive). If they used some form of DMA, then the UniDisk's CPU
> > > could be running at the same clock speed as the Apple II.
> >
> > The IIgs firmware manual covers the smartport calls , and the internal
> > memory map for the 65C02 in the Unidisk3.5.
> >
> > It uses an IWM chip which is clocked at 7MHz to achieve the 16ms/byte
> > you mention. The 65C02 is running at 2MHz.
> 
> How much RAM does the drive have?

There was another post in the thread mentioning it has 2 KB in total. 

That includes all space used for disk I/O buffers, zero page and stack
space, leaving you with approximately 1 KB of usable RAM, though you
might be able to stretch it to about 1.75 KB if you were able to reuse
the disk I/O buffer space.

-- 
David Empson
dempson@actrix.gen.nz