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From: dr@ski.UUCP (David Robins)
Newsgroups: net.micro.apple
Subject: Re: Enhancement Questions
Message-ID: <289@ski.UUCP>
Date: Wed, 13-Aug-86 21:46:07 EDT
Article-I.D.: ski.289
Posted: Wed Aug 13 21:46:07 1986
Date-Received: Thu, 14-Aug-86 21:43:58 EDT
References: <513@dg_rtp.UUCP>
Organization: Smith-Kettlewell Institute, S.F., CA.
Lines: 68

> Okay, gang, a couple of questions about the IIe enhancement kit:
> 
> My understanding is that I get
> 
> 	1) A new character generator ROM
> 	2) A new CD ROM
> 	3) A new EF ROM
> 	4) A 65C02 CPU

True.

> What are the differences between the old and new chargen ROMs?  As far as
> I can tell (by working on both a IIe and a //c), the inverse uppercase
> letters have been replaced with mouse icons.  Is this the only difference?

Yes

> Is the 65C02 pin compatible with my current 6502?  What new instructions
> do I get?  Do I lose any?  Where can I get a data sheet for the 65C02?

They are directly compatible, as long as you don't go back the other
way (6502 doesn't understand the new 65c02 instructions).  One problem
in any case:  the 6502 has a bug where addressing by JMP indirect
(code $6C) across a page boundary is incorrect ; instead of fetching the
high-byte from the next page, it fetches the high-byte FROM THE FIRST
BYTE OF THE SAME PAGE. 
The 65c02 fixed this so it operates correctly.  But, I am told,
some older software took the 6502 bug into account when writing the
software, and thus may work incorrectly with the 65c02 (Never program
taking "advantage" of a bug!).

The 65c02 has new modes: zero page indirect addressing,, and absolute
indexed indirect addressing (JMP instruction only).  Nothing is lost.
The 65c02 data sheet is in the free Apple publication, "About Your
Enhanced Apple //e: Programmer's Guide", #030-1143-A.  This NCR data
sheet is also in the new Apple //e Reference Manual, published by
Addison-Wesley, sold at bookstores.

> Did the published entry points for monitor routines stay the same in
> the new ROMs?  Are the new ROMs the cause of the longer interrupt
> handling times that was discussed here a couple of weeks ago?
> 
> 						Thanks,
> 						Karl
> 				Karl M. Owen
> 				Data General, RTP, NC
> 				...!seismo!mcnc!rti-sel!dg_rtp!owen

Most entry points stayed the same.  Where they published sections were
moved, they left a JMP to the new address.
Yes, the new ROMS's are the cause of the longer interrupt times, due
to a much longer interrupt processor before it gets to the user.  This
is to allow interrupts regardless of the state of the memory when the
interrupt occurred, such as being in aux memory, or bank-switched
memory.  Under the old system, the RTI would crash because it didn't
know where it was if the interrupt came while in the "non-standard"
state.

-- 
====================================================================
David Robins, M.D. 
Smith-Kettlewell Eye Research Foundation
(previously known as: Smith-Kettlewell Institute of Visual Sciences)
2232 Webster St; San Francisco CA 94115
415/561-1705 (voice)
			{ihnp4,qantel,dual}!ptsfa!ski!dr

The opinions expressed herein do not reflect the opinion of the Institute!