Replacing VAXen with VAX Emulation Presented at HP World 2003

1. Replacing VAXen
with VAX
Emulation
Stanley F. Quayle, P.E.
President
Quayle Consulting Inc.

2. Session goals
 Whether VAX emulation makes sense
 How to choose the best emulator and platform
 How to get started
07/09/09 HP World 2003 Solutions and Technology Conference & Expo page 2

3. What about porting?
 Do you have the design documentation?
 Do you have all the source code?
– What about DECmigrate (OMSVA)?
– VAX SCAN, Dibol, LISP, OPS5, RPG
 Operating system dependency?
 Hardware dependency?
 Target platform
– Can code really be reused?
– What about stability?
 Can you validate the result?
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4. Wine, FreeVMS, and ACCELR8
Application Application
Layered software
System libraries
System library
Operating System interface routines
CHARN-VAX
Host OS
Real
Host OS
Host CPU(s)
Hardware
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5. How hardware emulation
works
Application Application
Layered software Layered software
System libraries System libraries
Operating System Operating System
Emulator
CHARN-VAX
Real
Host OS
Host OS
Hardware
Host CPU(s)
CPU(s)
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6. The emulator task
Memory disk
Ethernet
CPU Disk controller
virtual disk
Emulation
Tape controller
Clock Serial ports virtual disk
tape image
System Serial External SCSI
Console Devices Tape & Disk
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7. CPU emulation
“TSTL XYZ”
 Retrieve state information from internal registers
 Fetch the instruction from memory
 Decode the operation to be performed
 Retrieve inputs from memory as needed
 Perform the operation
 Write results to memory as needed
 Update internal registers with the new state
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8. The emulator task
Memory disk
Ethernet
CPU Disk controller
virtual disk
Emulation
Tape controller
Clock Serial ports virtual disk
tape image
System Serial External SCSI
Console Devices Tape & Disk
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9. Cost versus benefit
 The high cost of downtime
– Customer impact
– “Above the Fold” on Wall Street Journal
– Data Loss
 Saving money on maintenance
– It’s cheap to replace a PC
– Limited support vendor choices
– Hardware support for some VAXen is unavailable
 Improved performance
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10. Available emulators
 Open-Source
– SIMH
– TS-10
– Others
 Freeware
– PicoVAX
 Commercial Product
– CHARON-VAX
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11. Open source or commercial?
 Open Source
– Free: Can be downloaded from the Internet, including
source code
– User-extensible
 CHARON-VAX
– Certified by HP as being a true emulation of a VAX
– Supports Q-bus hardware
– Dynamic Instruction Translation
– Training, installation, configuration, migration, and support
are available
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12. Evaluating the current
system
Major Items to Check
 CPU usage, memory size, number of users/processes
 Network
– Protocols: DECnet, IP, LAT, cluster, IEEE 802
– DECwindows
– Connections
 Disk drives: size, type, shadowing
 Tape drives
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13. Evaluating the current
system
Major Items to Check
 VMS version
 Layered product versions
 Application
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14. Evaluating the current
system
Risky areas
 Serial lines
– Terminal servers
– VAX serial lines
• Console
• Modem
– H3104, DHV-11, etc
 Licenses
– Network MAC address as “key”
– CPU characteristics as “key”
– VMS license requirements vs. emulated system
– “It works” vs. “Is it legal”
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15. Evaluating the current
system
There Be Dragons Here
 Operating systems
– NetBSD
– Digital Unix
– AT&T System V
– VAXELN
 Special hardware
– Bus: CI, M-bus, SBI, Turbochannel, UNIBUS, VAXBI,
XMI
– Disk interface: MASSBUS, SDI, ST-506 (MFM)
– Some hope for: DSSI, Q-bus
07/09/09 HP World 2003 Solutions and Technology Conference & Expo page 15

16. Special hardware: Q-bus
PCI bus Cable Q-bus rack
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17. Choosing the host platform
 Alpha OpenVMS
– Unquestionable stability
 Linux
– Inexpensive
 Windows
– Inexpensive
– Q-bus support
– “Industry standard”
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18. Sizing the host platform
“You can’t have too much”
 Server-class
– As fast as possible
 Memory
– More with DIT
 Processor
– Dual processors
 Disk
– SCSI
 Network
– Separate network adapter
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19. Performance
50 MicroVAX II
45 VAX 11/780
40 VAX 3100 model 80
35 VAX 4000, model 500A
30 VAX 4000, model 700A
25
VAX 7000, model 710
20
CHARON-VAX/XM on dual AMD 1.6 GHz
15
CHARON-VAX/Industrial on 2GHz Intel
10
5 CHARON-VAX/AXP on 1 GHz Alpha EV68
0 CHARON-VAX/XM Plus on 1.4 GHz dual CPU Intel
CPU model - VUPs (VAX Unit
CHARON-VAX/XM Plus on dual AMD MP2100+
of Performance)
Sources: HP and Software Resources International S.A.
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20. Disk migration
 Direct disk access
– SCSI? Just plug it in!
 Cluster
 Network
– COPY or COPY/FTP
– BACKUP
– MKIMAGE
– Poor Man disk driver
 Tape
 Serial
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21. Backup strategies
 Tape
 Network
– TCP/IP to host
– NFS
 Host
– Disk images offline
– Disk images online
– SCSI disks
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22. Write a plan
 Disk migration
 Backup scheme
 Necessary updates
 Test
– Connectivity
– Application
– Limited user access
 Going live
 Backout plan
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23. Post-migration
And they lived happily ever after…
 Hardware support
 Software support
 System administration support
 New versions
07/09/09 HP World 2003 Solutions and Technology Conference & Expo page 23

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