CPU

ace_mode

A CHARON-VAX emulated CPU is configured with the "ace_mode" parameter.

Two VAX CPU implementations are available: the standard VAX instruction decoder and the optional high performance Advanced CPU Emulation mode ("ACE"). The ACE option optimizes the VAX instruction interpretation and significantly improves performance. It also requires approximately twice the amount of host memory to store the optimized code.

ACE optimization is performed dynamically during execution. It does not need to write optimized code back to disk, ACE provides its full capability instantly. The optimization does not compromise the VAX instruction decoding; CHARON-VAX remains fully VAX hardware compatible and completely transparent to the VAX operating systems and applications.

Both CPU implementations passed the HP VAX Architecture (AXE) tests, the standard qualification for VAX instruction execution correctness.

The default VAX/PDP11 CPU mode is determined by the specific CHARON-VAX product license.

Parameter	ace_mode
Type	Boolean
Value	true or false

This statement enables the ACE mode if the CHARON-VAX license permits it. If this statement is omitted from the CHARON-VAX configuration file and the license permits it, "true" is the default, otherwise "false" is the default. For test purposes the ACE mechanism can be disabled with:

set cpu ace_mode=false

The command

"set cpu ace_mode=true"

is ignored when the license does not permit ACE operation.

The CHARON-VAX log file displays the status of the ACE option.

The ACE mode is disabled when the host system does not meet the minimum physical requirements for this operation. If the emulator appears to not run at its normal performance, check the log file for a change in the ACE mode and verify that sufficient host resources, especially memory, are available.

RAM

The CHARON-VAX / CHARON-PDP memory subsystem is permanently loaded and has the logical name "ram".

size

Parameter	size
Type	Numeric
Value	Size of the emulated memory in MB.

Example:

set ram size = 512

The amount of memory is capped at a maximum, this is defined in the CHARON license key. If the host system cannot allocate enough memory to map the requested emulated memory, CHARON-VAX / CHARON-PDP generates an error message in the log file and reduces its effective memory size.

The following table lists the values of emulated RAM for various hardware models of virtual VAX/PDP11 systems:

Hardware Model	RAM size (in MB)

Hardware Model	RAM size (in MB)
	Min	Max	Default	Increment
PDP1193	2	4	2	2
PDP1194	2	4	2	2
MicroVAX_II	1	16	16	1,8,16
MicroVAX_3600	16	64	16	16
MicroVAX_3900	16	64	16	16
VAXserver_3600	16	64	16	16
VAXserver_3900	16	64	16	16
VAXserver_3600_128	32	128	32	32
VAXserver_3900_128	32	128	32	32
MicroVAX_3100_Model_96	16	128	16	16
VAXstation_4000_Model_90	16	128	16	16
VAX_4000_Model_106	16	128	16	16
VAX_6000_Model_310	32	512	32	32
VAXserver_3600_512	32	512	32	32

Core Devices

Table of Contents

CPU

ace_mode

RAM

size