Re: Whats wrong with ROM 0 anyway?

[spec@vax2.concordia.ca (Mitchell Spector)]

In article martin.w6@ukonline.co.uk writes...

>The Apple 2 GS I have has ROM 0, no ROM is mentioned at
>powerup. I also suspect it has the early faulty video chip
>as I ran Elite on it and there was colour fringes on the
>black and white action screen. The monitor I'm using is a
>0.28mm multiscan and isn't the cause.

    A faulty VGC chip is easy enough to identify, it will
have a '-A' or '-1' suffix ending on the chip part number
(e.g. 344S0046-1). Generally you can tell if you have one
because you'll see stray bits of inversed and/or flashing
pink in between 80 column text characters and over parts
of any monochrome Double-Hi-Res 560x192 screen (not to be
confused with color fringing that occurs in all Apple II's).

>What disadvantages are there to having ROM 0?

    You won't be able to run *any* version of GS/OS, which
means your limited to System 3.2 or lower. Another issue
is the majority of Apple IIgs software written in the past
10-11 years will refuse to run.

    Other than having the old, outdated System 1.0 toolsets
in firmware and several stray bugs, the only other issues
are the maximum RAM Disk size you can set is 4 MB and you
have a more limited system Monitor (you cannot type "#" as
a shortcut to invoke the programmer CDA's and there is no
command to put the 65C816 into 16-bit native mode).

>The computer seems fully usable but what problems should I
>expect?

    If you plan to use it only to emulate an Apple IIe, then
the ROM 00 is absolutely fine. Then there are no issues to
worry about (unless you happen to have lots of memory inside
the system and want a huge RAM Disk for ProDOS-8; doubtful
since there is no reason to have a lot memory installed in a
ROM 00, considering it can't run very much native Apple IIgs
software. You can still play Zany Golf though). :)

Mitchell Spector
spec@vax2.concordia.ca