Date:  Tuesday, July 19, 1994 12:29:57 AM
Author:  Apple Computer, Inc.
Subject:  A/ROSETM1.2.1

Equipment:  Macintosh

Summary:  Includes the A/ROSE v1.2.1 System Extension, including the 
associated interface files and object modules.  Latest update for the 
A/ROSE software, v1.2.1, required for Apple Macintosh Coprocessor based 
NuBus cards such as the Ethernet NB, TokenTalk NB, and TokenRing 4/16 NB 
cards running on the PowerPC system.

Addresses a compatibility issue with operations on the PowerPC.  

o When VM was inactive and the processor was not a 68040, A/ROSE 1.2 left 
a block of shared motherboard memory used by NuBus cards unlocked and 
cachable.  This improved performance on 68030-based Macintoshes (see the 
release notes for A/ROSE 1.1.8).  For performance reasons, the 68040's 
data cache(s) are implemented very differently than the 68030's, so the 
A/ROSE driver must leave the shared memory locked and non-cachable on 
68040-based Macintoshes.

The PowerPC emulation mode emulates a 68020 so thoroughly that even 
Gestalt reports that the processor is a 68020.  However, the 601 chip's 
data cache implementation is similar to the 68040's.  Because Gestalt 
reported the processor as a 68020, the A/ROSE driver was unlocking the 
shared memory, causing a hang on PowerPC machines.  The problems did not 
occur when VM was active, since A/ROSE must keep the shared memory locked 
to prevent the memory from being paged to disk or relocated, regardless 
of the processor.

The fix was to check the new Gestalt system architecture selector, 
'sysa', to determine the family of the processor on the motherboard 
(68000 family or PowerPC family).  If the processor is a PowerPC, A/ROSE 
leaves the shared memory locked down even though the PowerPC is emulating 
a 68020.

o On PowerPC-based Macintoshes, A/ROSE now page-aligns the block of 
shared motherboard memory used by NuBus cards and pads the memory out to 
the next page boundary.  This prevents other memory surrounding the 
shared memory from being made noncachable when the block is locked down 
using LockMemory.  This code was already being executed on 68040-based 
Macintoshes, but it's now also being executed on PowerPC-based machines.

Requires:  System 6.0.5 or greater, MacPlus or later CPU.

Keywords:  A/ROSE, MCP, Macintosh Coprocessor Platform, Ethernet NB, 
PowerPC, Network Software, AppleTalk, TokenTalk, Token Ring
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