Chapter 3. FLEX-ES and OS/390 installation 17
Figure 3-1 Conceptual view of FLEX-ES system
Key points include:
FLEX-ES is a software product.
2
All the hardware shown (in Figure 3-1) is standard
ThinkPad hardware.
The FLEX-ES program, running under Linux on the ThinkPad’s PC processor, emulates a
complete S/390 environment.
– FLEX-ES obtains sufficient virtual memory to emulate the “real memory” for the
defined S/390 machine being emulated. While not detailed in the illustration, FLEX-ES
can also emulate expanded memory.
– FLEX-ES, as part of emulating a S/390, handles S/390 I/O instructions and emulates
the S/390 I/O devices as required. In the illustration, various 3390 volumes (containing
OS/390 and so forth) are contained on the ThinkPad disks.
The FLEX-ES license specifies how many PC processors may be used (at any one
instant) for S/390 emulation. For a ThinkPad/EFS system this will normally be one
processor.
The owner can elect to dedicate PC processor(s) to FLEX-ES S/390 use. This provides a
performance boost. You cannot dedicate all the PC processors to S/390, because other
Linux functions need access to a processor. If processors are not dedicated, then the
normal Linux dispatching function will dictate which processors are being used by
FLEX-ES at any instant. The number will never exceed the number permitted in the
FLEX-ES license. A ThinkPad/EFS system has only a single PC processor, and it cannot
be dedicated for S/390 emulation.
2
The optional S/390 channel adapters available for use with FLEX-ES are ignored in this discussion.
PC Processor in ThinkPad
Enet Adapt
Linux operating system
FLEX-ES processes
Emulated S/390
running OS/390
and its normal
applications
other Linux
processes
FLEX-ES
Terminal Solicitor
TCP/IP
LAN
ThinkPad
display and
keyboard
Windows
ThinkPad disks
