Re: GS 65816 Chip??

[ballweb@PEAK.ORG (Brian Ballweber)]

Nathan Mates (nathan@cco.caltech.edu) wrote:
: In article <3qetpp$ql4@triode.apana.org.au>,
:    If a 65816 is working in a 6502-designed motherboard, good for you.
: As to damage or anything else, I really can't comment further. Maybe
: some of you Electrical ENgineers can comment further.

According to my venerable Apple Thesaurus, here is some info about the '816:

The 65816 has 5 new control lines over the 6502 design:
  VPA (Valid Program Address)
  VDA (Valid Data Address)
  ABORT
  VP  (Vector Pull)
  ML  (Memory Lock)

The memory lock signal is used for multiprocessor systems to inform other
processors that the 65816 is performing a "read, modify, write" instruction
such as a DEC of a data value in memory and thus cannot relinquish control of
the bus.

The vector pull is used to announce that it is starting to handle an interrupt.

The VPA, VDA, and ABORT lines are used to implement a memory management system
and/or a cache memory architecture.  (Incidental bit of trivia: according to
the Apple Thesaurus the 65816 which was introduced in 1984 was the first
microprocessor other than a DEC Micro Vax1 which had a "cache" oriented memory
design)

As far as the pinouts, here would be the result of using a 65816 in place of
a 65802 <ill only list the pins that are different>:

Pin         65816 usage                    65802 usage
---         -----------                    -----------
 1            /VP     vector pull            Vss       connect to +Vss
 3            /ABORT  abort                  01(out)   phase 1 out clk
 5            /ML     memory lock            NC        no connect
 7            VPA     valid prog addr        SYNC      synchronize
 26           D7/BA7                         D7
 27           D6/BA6                         D6
 28           D5/BA5                         D5
 29           D4/BA4  8 data/bank            D4        8 data
 30           D3/BA3                         D3
 31           D2/BA2                         D2
 32           D1/BA1                         D1
 33           D0/BA0                         D0
 35           E       emulation sel          NC        no connect
 36           BE      bus enable             NC        no connect
 38           M/X     mode select            /SO       set overflow
 39           VDA     valid data addr        02(out)   phase 2 out clk

Im not sure of the 6502 pinouts, but since this operation would require
the functions of the 65802 you can skim the list and see if anything would
be bogus.  Several places ive read that the 65802 is pin compatible with
the 6502, but that has never been said for the 65816.  If this does indeed
work in place of a 6502, my guess is that several pins such as 3,7,38, and 39
are not being used since the corresponding 65816 pin has a completely
different usage.
 
- Brian
  Digital Exodus