Re: Second Sight SVGA Board Tech Info

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

In article <36o6uh$ma0@quartz.ucs.ualberta.ca>,
Jerry Penner <jpenne@ee.ualberta.ca> wrote:

[snip]

> Is Z180 code in general relocatable, so that if my program has
> downloaded some stuff and your program also downloads some, they
> won't conflict? 

Definitely not.  The Z180 has the same instruction set as the Z80,
with a few extras such as multiplication.  I would hardly call the Z80
relocatable, though you can write relocatable code with a little hard
work and messy use of registers (no long branch instructions, though).

> I don't know anything about the Z180 (but it sounds an awful lot like
> a Z80 that's somehow had a bus/instruction set upgrade), so I would
> like to know why it was chosen.

Dirt cheap, and it has already been used in the RamFAST.  It is a very
nice chip, with an extended Z80 instruction set, plus on-chip Z80
support circuitry such as timers, interrupt controller, memory
manager, and extended addressing support (1 megabyte address space).

> Does the Z180 have an instruction cache?

I don't think so.  No data book handy, so I can't check the details.
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand