HP 9020 User Manual

2-52 Theory of Operation
Bootstrap Loader Card
The bootstrap loader card plugs into 70-pin connector PIlon the 110 backplane and shares select
code 7 with the
9130K Flexible Disc Drive controller card. The bootstrap loader card is designated
Unit 1, and the controller card is designated Unit O.
The bootstrap loader card contains up to 8K bytes of ROM which holds loader code and machine
ID information for protection of software rights. The card provides a boot loader when there is no
Winchester fixed disc drive
in the computer. If the Winchester is present, the boot loader circuitry is
located on the Winchester disc controller.
Figure 2-26
is the bootstrap loader card block diagram. The card has three main functional blocks:
1) 8K bytes of loader ROM, 2) a 16-bit counter for addressing, and 3) system control logic. The
loader
ROM is configured for byte addressing only. The 16-bit counter consists of two dual 4-bit
counters which address the
ROM directly. The counter is automatically incremented after reading a
byte of data from the
ROM. The counter is reset to address 0 with the IFC signal or by reading FR3,
the
ID register. The control logic determines which data to place on the 110 lines, which direction
the data flows,
and the proper clock signals for latching data.
Boot Loader ROM
If the Processor Stack contains 1 Megabyte RAM boards, Boot Loader ROM Rev. B (09020-
80001)
must be used, and UNIX 4.0 or basic 2.0 software must be used.
Boot Loader
ROM 09020-80000 can be used with UNIX 4.0 or Basic 2.0 (or any previous software
versions) as long as the stack
DOES NOT contain a 1 Megabyte RAM board.
Boot Loader
ROM Rev. B (09020-80001) can be used with any RAM configuration but MUST use
UNIX 4.0 or Basic 2.0 software. (Any earlier versions of software cannot be used with this boot
loader.)

HP 9020 Specifications

General

Brand	HP
Model	9020
Category	Desktop
Language	English