Re: Upgrading an Unenhanced IIe

["Michael J. Mahon" <mjmahon@aol.com>]

Great Hierophant wrote:
> Couldn't you do the ROM upgrading yourself?  The three ROMs that are
> replaced can be done with burned EPROMs.  The code is available (thanks
> to MESS), but will the EPROMs work without rewiring?

Yes, 2764s and 27C64s work fine.

> Of course, doing this would be foolish without also replacing the
> processor.  But are there multiple varieties of 65c02 processors?  If
> so, can anyone suggest a good place to obtain them.

It's not "enhanced" unless it has a 65C02 processor.

> Finally, Apple must have rewired the unenhanced IIe board to allow it
> to do DHGR.  They certainly didn't add any new chips to the design.
> So, modifying the board must be possible.  The only question is whether
> it is so involved as to be not worth the trouble.

As was noted by another poster, DHGR was not an "enhanced" feature,
but a very early //e board revision.

AFAIK, the only board change was routing the AN3 output to the
AUXMEM slot to control DHGR.  The gating is on the RAM board and
is the same gating used for 80-column text display.

-michael

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