[comp.sys.amiga] Limit on ROM size

jwright@atanasoff.cs.iastate.edu (Jim Wright) (03/24/89)

In article <11039@well.UUCP> ewhac@well.UUCP (Leo 'Bols Ewhac' Schwab) writes:

[ all context deftly removed :]

| 	Nice, but there's no room in the ROM for it.
| 
| Leo L. Schwab -- The Guy in The Cape	INET: well!ewhac@ucbvax.Berkeley.EDU

This is something I've been wondering about.  Is the Amiga (other than
the 1000) inherently limited to 256K ROMs?  At the price of losing some
compatibility with 1000's, how easy is it to install larger ROMs?  Could
a 512K, 1M, etc. sized be easily used or is the hardware limited to
addressing only 256K?

(I don't want to start a religious war, I'm just curious.  No flames from
1000 fans, please.)

-- 
Jim Wright
jwright@atanasoff.cs.iastate.edu

mp1u+@andrew.cmu.edu (Michael Portuesi) (03/25/89)

jwright@atanasoff.cs.iastate.edu (Jim Wright) writes:
> In article <11039@well.UUCP> ewhac@well.UUCP (Leo 'Bols Ewhac' Schwab) writes:
> 
> |       Nice, but there's no room in the ROM for it.
> | 
> | Leo L. Schwab -- The Guy in The Cape  INET: well!ewhac@ucbvax.Berkeley.EDU
> 
> This is something I've been wondering about.  Is the Amiga (other than
> the 1000) inherently limited to 256K ROMs?  At the price of losing some
> compatibility with 1000's, how easy is it to install larger ROMs?  Could
> a 512K, 1M, etc. sized be easily used or is the hardware limited to
> addressing only 256K?

The 500 and the 2000 can definitely support 512K of ROM, though I
don't think the software designers want to do that just yet.

As for A1000's, I asked this question a long time ago, and I think the
answer is that the A1000 can also support 512K of ROM space, though it
is not straightforward (you have to cut a trace or change a PAL or
something like that).

Could someone from Commodore please correct me if I am wrong, or add a
few more details?

--
Michael Portuesi / Information Technology Center / Carnegie Mellon University
INET:   mp1u+@andrew.cmu.edu / BITNET: mp1u+@andrew
UUCP:   ...harvard!andrew.cmu.edu!mp1u+

	"You just don't get off a spaceship and run." --Avon

daveh@cbmvax.UUCP (Dave Haynie) (03/29/89)

in article <904@atanasoff.cs.iastate.edu>, jwright@atanasoff.cs.iastate.edu (Jim Wright) says:
> 
> This is something I've been wondering about.  Is the Amiga (other than
> the 1000) inherently limited to 256K ROMs?  At the price of losing some
> compatibility with 1000's, how easy is it to install larger ROMs?  

A500s and A2000s are designed to accept a pin-compatible 512K ROM.  The main
reason for NOT building a 512K ROM today is the extra trouble A1000 owners
would have, I suspect.  Beyond 512K, you run out of address lines on the
physical ROM and address space to put it in, so today's machines are basically
limited to 512K.

> Jim Wright
> jwright@atanasoff.cs.iastate.edu
-- 
Dave Haynie  "The 32 Bit Guy"     Commodore-Amiga  "The Crew That Never Rests"
   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: D-DAVE H     BIX: hazy
              Amiga -- It's not just a job, it's an obsession

michael@stb.UUCP (Michael) (03/31/89)

Actually, how significant is ROM size as a limit anyways?

Just use RAM. Patch some library vectors, install a ROM-TAG to re-do the
vectors at every warm boot, presto! No need to hack up some ROM.

BTW, can we please see this in 1.4, i.e., if we have a 500 or 2000 with 1.2
roms, how about putting a rom-tag'd patch program in to give us all the
1.4 features without needing new roms? We've got the memory now.

			Michael
: --- 
: Michael Gersten			 uunet.uu.net!stb!michael
:	michael@stb.uu.net <mx mailers>	crash!gryphon!denwa!stb!michael
: "Robitussin" for computers? This has gone too far. Where's "Penicillian"?
: (rob. is Coff-medicine to let COFF people run bsd-dependent GNU stuff).