HP 330 Service Information Manual page 73

Unsupported Accessories
The following accessories are not supported in Models 330/350 computer systems:
• HP 98254A 64 Kbyte RAM Card.
• HP 98256A 256 Kbyte RAM Card.
• HP 98257 A 1 Mbyte RAM Card.
• HP 98603A ROM BASIC 4.0.
• HP 98603C ROM BASIC 5.0.
• HP 98620A Two-Channel DMA Interface.
• HP 98635A Floating-Point Math Card.
• 98561-66531 Human Interface Card.
Model 350 Processor Board
A new high-performance processor board is used in the Model 350. This board uses the 25 MHz
MC68020 processor and the 20 MHz MC68881 floating point co-processor. It also contains a 32
Kbyte high-speed instruction/data cache, a memory management unit, a MC6840 timer, and
two Boot ROMs.
Model 330 Processor Board
On this processor board, the MC68020 CPU and MC68881 co-CPU are clocked at 16 MHz.
Although no cache is used, the MC68851 memory management unit is. On-board RAM of 4
Mbytes makes the Model 330 processor board powerful in its own right. RAM control and byte
parity is sinlilar to the 4 Mbyte RAM Controller Board.
Timer, Boot ROMs, and self-test LEDs are the same as the Model 350, as well as the same
DIO-II and DIO bus capability. A system bus cannot used on the Model 330, therefore memory
cycles will be slower than the Model 350.
Model 350 System Bus
On the Model 350 back panel, you will notice the cover plate over the processor and memory
boards has a connector board mounted inside. This connector provides a high-speed memory
bus between the Model 350 processor board and one or two RAM controller boards. This
"connectorized" cover plate is called the system bus.
Model 350 RAM is tightly coupled to the Model 350 processor through the system bus. This
allows much faster memory cycles and larger memory boards. It supports both 32-bit address
and data. It also supports 16 byte cache line sustained read cycles at over 22 Mbytes/second.
Single write-cycle sustained transfer rate on the system bus is 14.3 Mbytes/second.
Memory Boards
Each 4 M[byte RAM Controller Board, and optional 4 or 12 Mbyte add-on board, uses one
system slot. With this arrangement, 4, 8, or 16 Mbyte RAM assemblies are provided. The
maximum amount of RAM in the system is limited to 32 Mbytes in a Model 350 and 8 Mbytes
in the Model 3:30, Configuration is set by switches on the RAM controller board and Model 330
processor board.
Functional Description
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