GE 645

[5] General Electric initially publicly announced the GE 645 at the Fall Joint Computer Conference[1][3] in November 1965.

At a subsequent press conference in December[6][7] of that year it was announced that they would be working towards "broad commercial availability"[8] of the system.

Instead both sets of functionality was combined into one unit called a GIOC (Generalized I/O Controller) which provided dedicated channels for both Peripheral (Disc/Tape) and Terminal I/O.

[4][12] The GIOC acted as an Active Device and was directly connected to memory via dedicated links to each System Controller that was present in a specific configuration.

The Extended Memory Unit, though termed a drum, was in reality a large fixed-head hard disk with one head per track,[13] this was a OEM product from Librascope.

Interrupts can be inhibited and instruction fetching is limited to a 218 (18-bit) absolute address thus restricting the processor to only been able to access the lower 256 KW of physical core memory.

The processor will switch to this mode in the event of a fault or interrupt and will remain in it until it executes transfer instruction whose operand address has been obtained via the appending process.

Indirect words and operands are accessed via Appending Mechanism via the process of placing a 1 in bit 29 of the executed instruction.

[4]: 18, 22 [15] The instruction format with bit 29 set to 1 is: The GE 645 had 8 Address Base Registers (abr's),[17] these could operate in either "paired" or "unpaired" modes.

CTSS had originated in the MIT Computation Center using a IBM 709 and was first demonstrated in November 1961,[22] it was subsequently upgraded to a 7090 in 1962,[23] and finally to a 7094 in 1963.

During this period exploratory work was carried out into what a replacement for CTSS would look like and what type of hardware it would require to run on.

A committee was formed consisting of Fernando J. Corbató, Ted Glaser, Jack Dennis and Robert Graham with responsibility to visit computer manufacturers to gauge level of interest in the industry to tender for the hardware platform.

[26][27] It was made clear that Project MAC was looking for a development partner given the considerable hardware modifications that would be required to meet their requirements, which were specified as:[28] They proceeded to visit among others Burroughs, CDC, DEC, General Electric, IBM and Sperry Univac.

[33] The bulk of these computers running time-sharing on Multics were installed at the NSA and similar governmental sites.