Xi 8088

Introduction

Xi 8088 is an IBM PC/XT compatible processor board in ISA board form factor. It offers several enhancements over the standard IBM PC/XT, such as support of PS/2 keyboard and mouse and built-in real time clock with NVRAM (also known as CMOS setup memory).

Picture

Specifications

- Processor: Intel 8088 or compatible, NEC V20.
  - Supports both standard 4.77MHz CPU clock and turbo, up to 13.33MHz CPU clock operation.
- Coprocessor: Intel 8087.
- RAM: Up to 832 KiB of usable system memory (640 KiB base memory, and up to 192 KiB UMB); Implemented using SRAM.
- ROM: 128 KiB flash ROM. Configurable to either 64 KiB or 128 KiB.
- 8-bit ISA interface with several ISA/AT signals
- PS/2 compatible keyboard and mouse controller
- One 8237 direct memory access controller (DMAC)
- Two 8259 programmable interrupt controllers (PICs), supporting the total of 15 interrupts; 10 interrupts available for extension cards
- One 8254 programmable interval timer (PIT)
- One DS12885/DS12887 real time clock and non-volatile RAM (RTC/NVRAM)

Firmware / BIOS (files are at the bottom of this page)

bios-0.9.0.tar.gz - Use bios128k-2.0.bin for programming new flash ROMs; use bios.bin with xiflash utility. Please refer to README.txt for more information about the BIOS.

xiflash-0.1.tar.gz - In system flash programming utility.

Hardware Documentation (files are at the bottom of this page)

Schematic

8088-SBC - Schematic - Color - 2.0.pdf

PCB Layout

8088-SBC - Board - Color - 2.0.pdf

Memory Map

I/O Ports Map

Hardware Interrupts

Jumpers, Connectors, and Switches

P1 - PS/2 Keyboard

P2 - PS/2 Mouse

P3 - Speaker

*Note: To enable internal speaker connect a jumper across pins 1-2

P4 - Power LED

Description

LED's anode (+)

LED's cathode (-)

P5 - Turbo LED

Description

LED's anode (+)

LED's cathode (-)

J1 - Reset Switch

Description

Ground

Reset input

J2 - Turbo Switch

* Default setting

J3 - IRQ12

Position

1-2*

2-3*

Description

IRQ12 is PS/2 mouse interrupt - connected to the keyboard controller

IRQ12 is connected to the ISA bus

* Default setting

J4 - Enable ISA16 signals

Note: Set all jumpers for Cirrus Logic GD542x VGA cards, remove for all other cards.

J5 - Clear NVRAM

Position

none*

1-2

Description

Normal operation

Clear NVRAM (CMOS setup memory)

* Default setting

SW1 - Reset Switch

Press SW1 to reset the system

SW2 - Memory Configurations Switch

Notes:

- SW2.7 must be ON if SW2.5 or SW2.6 are ON
- VGA BIOS is usually mapped to 0C0000h-0C7FFFFh, when using VGA SW2.1 must be OFF

SW3 - I/O Wait States Configuration Switch

* Default

Note: One and only one of SW3 switches must be on

Bill of Materials (BOM)

BOM Notes

BOM

Replacement Notes

- Intel 8xxx ICs - Either CMOS (8xCxx) or NMOS/TTL ICs can be used. CMOS and particularly NEC V20 CPU and Intersil 82Cxx peripheral ICs are preferred because of their lower power consumption and higher performance
- 74xx logic ICs - Advanced TTL-LS (74ALS, 74F) or advanced TTL compatible CMOS (74AHCT, 74ACT) are recommended, especially for turbo CPU clock frequencies. Some parts (74LS92, 74LS06, 74LS670) are not available in these series, so regular 74LS and 74HCT should be used. With that being said most of logic parts are not very speed sensitive, especially if running on standard 4.77 MHz clock, with exception of 74ALS74 in wait state generator, so generally 74LS series ICs can be used. 74F and 74ACT are preferred parts for bus driving circuits (74x244, 74x245, 74x573)
- For higher clock frequency (more than 8 MHz) along with 74ALS or 74AHCT for most logic, it is recommended to use faster U31, U32, U24 and U25. For example 74F or 74ACT series.

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