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The IMSAI 8080


4K Random Access Memory RAM 4A-4

The basic memory is the 4K Random Access Memory (RAM 4A-4). This board stores 4096 bytes of changeable information, either programs or data. Information may come from a computer program, a peripheral device, or the front panel switches. 

RAM 4A-4 offers a number of unique features to make program development easier. A powerful memory write-protect feature lets you protect 1K-byte blocks of data under program or front panel control. The program can test for the protect status of any 1K-byte block, and an interrupt is generated when a protected block is illegally accessed. 

The board has two LED indicators for each 1K-byte block. One is lit when the block is write-protected, and the other is lit when the block is being accessed for reading or writing. 

Storage is static using 2102-type chips (no refresh cycle) with a cycle time of 500 nanoseconds. The board address can be jumper-selected to any 4K block of the computer's 64K-byte address space. The memory is fast enough so that no wait cycles are required. If you use slower memory chips a wait cycle can be generated. Tn-state bus drivers and three fully decoupled oncard voltage regulators are used. 

The board also includes a battery backup circuit (battery not included) to save memory contents when ac power is turned off. Each RAM 4A-4 board requires one edge connector (EXPM). 

1K Random Access Memory RAM 4A-1

The 1K Random Access Memory (RAM 4A-1) stores 1K bytes of information. Except for memory capacity, it has the same specifications as the RAM 4A-4 board. As your needs increase you can add memory capacity up to 4K, in 1K increments, by adding MMO2-l memory modules. This board is available only with the IMSAI I-8080-1K computer system. 

Requires one edge connector (EXPM). 

1K Memory Module MMO2-1

This is the 1K-byte RAM memory module (MMO2-1) used to add storage capacity to a RAM 4A-1 board. 

8111 Memory Module M11-1 

This 8111-type 1K-byte memory module (M11-1) is used to add storage capacity to the RAM 4-1 board, now discontinued. 

Read Only Memory PROM 4-4

This board (PROM 4-4) provides non-volatile program storage that cannot be changed by the computer or erased when power is turned off. Use a PROM board for programs that are run frequently. For example, IMSAI provides the BASIC language in PROM. 

The board contains 16 Intel 1702A, or equivalent, EPROM chips in sockets. They may be erased by ultraviolet light and can be reprogrammed electrically by a PROM programmer unit. Each device stores 256 bytes for a total of 4K bytes on the board. Each of the 16 PROM sockets is individually addressable and PROM's operate independent of each other. Thus, memory space may be structured by simply arranging PROM's in appropriate sockets. The board address is jumper-selected to any 4K block of the computer's 64K memory space. A user-selectable memory-read delay (0 to 3 machine cycles) allows most efficient use of fast or slow PROM chips. The chips supplied have an access time of 1000 nanoseconds. 

The board includes tn-state bus drivers and fully decoupled supply voltage regulators. An EXPM edge connector is required to install the board. 

512 Bytes PROM Memory PROM 4-512

This is a memory board (PROM 4-512) with only two PROM chips that provide 512 bytes of PROM storage. The board may be fully populated, in 512-byte increments, up to 4K bytes by adding 512 Byte Memory Module (MM702-5) sets. An EXPM edge connector is required. 

512 Bytes PROM Memory Module MM702-5 

This is a set of PROM chips (MM702-5) to add 512 bytes of storage to a PROM 4-512 board. 


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