HP 330 Service Information Manual page 96

On-Board RAM
Memory on the Model 330 processor board is similar to the 4 Mbyte RAM controller board.
It's like the RAM controller board, but simpler in operation. A comparison between the RAM
section of Figure 3-16 and the RAM controller diagram in Figure 3-19 shows the difference.
RAM Control
The DIO-II bus handles all data and address transfers. It also supports DIO bus masters. The
system bus is not used on the Model 330 processor; there is no connector on the processor board
for it.
RAM Configuration
Configuration of the Model 330 processor's 4 Mbytes of RAM is set by 10 dip switches. These
switches allow the RAM controller to adjust to the CPU as well as configure in the optional 4
Mbyte and 12 Mbyte add-on board sizes. Processor board on-board RAM top address is set by
these switches.
Switches are set to one of the 4M address boundaries starting at the top of RAM, address
FFFFFFFF. Only the three most significant digits (MSD) of hexadecimal addressess are af-
fected. As the first eight switches (S31, S30 ... S24) represent the two MSDs, the last two
switches (S23, S22) can only change the third hexadecimal MSD by 4M addresses; the lower
two binary positions of the third hexadecimal digit are implied as 1.
Two configurations are possible for Model 330 computers. They are shown in the next section
under RAM Configuration.
Optimizing Model 330 System Performance
Each of the Series 300 operating systems (BASIC, Pascal, and HP-UX) are booted into different
memory address ranges. Application programs are loaded into other memory address ranges.
Depending on the operating system and application program used, frequently accessed memory
addresses mayor may not be in processor on-board RAM. If optimum performance is desired
fot a given application, this Inay be possible by readdressing processor on-board RAM to the
addresses frequently accessed by the application.
Cycle time for processor board RAM is less than for HP 98258A/B/C RAM assemblies. This is
due to the longer read/write cycles on the DIO-II bus to the optional 4 Mbyte RAM controller
board. You may configure the Model 330 computer's memory so the application program spends
the maximum amount of time executing in the processor's on-board RAM.
If a Model 330 computer system has the maximum of 8 Mbytes of RAM, one of the two con-
figurations shown in Table 3-5 will optimize that system's performance. Here's what to do to
determine which configuration works best:
1. Select a frequently-used program or routine as a benchmark.
2. Run and time the benchmark program enough to determine that it consistently executes
in the same length of time.
Note: in this example, memory is now addressed as shown in Table 3-5, Example 1.
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Functional Description