- 2 -
PART 1 – ALTAIR 8800 CLONE HARDWARE SPECIFICATIONS
A. RAM
64K of RAM with memory protect in 256 byte pages. If any PROMs are loaded and
enabled, the overlaid RAM is replaced by PROM in 256 byte increments.
B. PROM
Eight “sockets” of up to 2K each provide for up to 16K of PROM. Loaded and
enabled PROMs overlay and replace RAM in 256 byte increments. A feature pre-
sent in the 8800b Turn-Key computer to disable PROM (in order to re-enable
RAM) can be turned on if desired. See “Administration Menu” in Part 2, “Con-
figuration Monitor” for more information.
C. Serial Ports
Two serial ports are wired to DB-25 connectors on the rear of the computer.
The port types can be configured to match original Altair hardware as shown
below. The optional Audio Cassette Interface adds the third serial port. The
first row illustrates the default configuration.
Serial Port 1
(Top Connector)
Serial Port 2
(Bottom Connector)
Serial Port 3
(from Cassette Intf)
First port from 88-2SIO
board at I/O address oc-
tal 20/21
88-SIO port at I/O ad-
dress 6/7 (the Altair
cassette serial port)
First port from a second
88-2SIO board at I/O ad-
dress octal 24/25
88-SIO port at I/O ad-
dress 0/1
Second port from 88-2SIO
board at I/O address oc-
tal 22/23
88-SIO port at I/O ad-
dress 6/7 (the Altair
cassette serial port)
The serial ports are wired as follows:
Pin Signal
2
3
4
5
7
XMT from Terminal (out) to Clone (in)
RCV to Terminal (in) from Clone (out)
RTS from Terminal (out) to Clone (CTS in)
CTS to Terminal (in) from Clone (RTS out)
Signal Ground
By default, pin 4 RTS (which becomes CTS inside the Clone) is always asserted
inside the Clone and therefore does not need to be connected on the DB-25 if
active handshaking is not used. RTS is not present or used on Port 3.
By default, pin 5 CTS (which is driven from RTS inside the Clone) is always
asserted in case an asserted handshake signal is required by the peripheral
device. CTS is not present or used on Port 3.
The ACIA on the 88-2SIO board supports programmed hardware handshaking. If
your applications requires this feature, the ACIA’s handshake lines can be
configured to be fully active. See “Set CTS, RTS Usage” in the “Serial Port
Menu” section of Part 2, “Configuration Monitor” for more information.
D. Line Printer Port
The Altair Clone implements the Altair 88-LPC line printer interface board.
This board is supported by Altair BASIC, Altair DOS, CP/M 1.4 and CP/M 2.2.
When prompted for the printer type in Altair BASIC or Altair DOS, choose “O”
(capital letter “oh”) to select the 88-LPC interface.
To Next Page
