The initial 1984 US version named AT&T 6300 came with either one or two 360 KB 5.25" floppy drives; a hard disk was not offered.In Europe, Olivetti launched a 10 MHz version: the Olivetti M24 SP, announced in November 1985,[9] a contender for the title of "highest clocked 8086 computer" as its processor was the fastest grade of 8086-2, rated for a maximum speed of exactly the same 10 MHz.

The CPU clock, along with most others in the machine (other than the serial baud rate generator and an IBM-standard 14.3 MHz crystal used on the expansion board), was divided down from a 24.0 MHz master crystal, with the CPU timing in particular using an Intel 8284 clock generator, as per the IBM PC, to produce the 33% duty cycle pulse wave required by the 8086.

The system was designed "split-level", with the motherboard screwed onto the underside of the computer case and connected to the ISA bus backplane in the top section of the case via the video card which, rather than occupying an ISA slot, has two female edge connectors and plugs onto the ends of both the motherboard and the backplane, doubling as a bridge between them.

The machine had the bad luck of launching just a few months before the IBM PC/AT, which introduced the entirely different 16-bit connector and signalling standard extension to the PC bus now known simply as "ISA", and so ended up featuring slots incompatible on all three fronts of physical configuration, complement and arrangement of signals, and data transfer rate, significantly restricting the number of compatible 16-bit cards produced for it.

All modes were non-interlaced, albeit running at a then-common 50 Hz Vsync rate, and required the dedicated OEM 26.3 kHz, 12" monitor (either colour or multi-level monochrome) because of their comparatively high line frequency, with all but the M20 mode using the 24 MHz system master crystal to drive the pixel clock either directly or (320×200 and 8×16 40-character only) divided in two (in comparison, contemporary IBM displays ran at 15.8 to 21.9 kHz with 14.3 to 16.3 MHz dot clocks).

[27] Colour depth remained the standard fixed 4-colour CGA palettes in 320×200, and "monochrome" in all higher modes (any selectable RGB(I) foreground colour/one of 15 shades, with a fixed black background), but could be expanded to 4 or 8 colours/greyscales in all resolutions, and 16 in all but 512×256, with the addition of a graphics memory expansion board holding between 32 and 96 KB RAM (the resolution:colour relationship being unintuitive due to Motorola HD6845 CRTC bandwidth and addressing limitations - 16 colours in the 640-pixel modes effectively combined the standard and expansion memory spaces into a single 64-bit wide bank); the expansion card also had its own monitor port built in allowing native dual-monitor support.

CGA compatibility was necessarily limited to "RGB" modes, and "well behaved" software that only used the BIOS-preset modes and didn't attempt too much clever direct reprogramming of the CRTC registers (including setting of pseudo-text hack modes like 160×100 16 colours), as there was no composite video output available and although some basic register settings remained the same, others were necessarily very different because of the line doubling trickery (itself a type of CRTC hack) and altered scan rates, and Olivetti's protective "scrambler" chip that attempted to convert custom settings to the nearest safe equivalents could only go so far.

In its turn, the machine's headline 640×400 graphics mode received a moderate level of support from software developers, mostly for "serious" applications such as Lotus 1-2-3 and Symphony (Earl Weaver Baseball is however an example of a game that can use it), and was for a time both supported and emulated (as well as extended to e.g. 752x410) by various "Super EGA"/"any mode on any monitor" cards such as the ATI EGA Wonder.

However, the original graphics card had to remain in place even if no longer in use, as it formed an essential part of the bridge connecting the expansion board to the motherboard, and although it featured DIP switch jumpers to select between MDA/Hercules, 40 and 80 column CGA, and expanded video options including its own (as per the IBM motherboard settings), there was no "disable" switch.

Some plasma-screen and early LCD based portables from Compaq and other manufacturers also copied the M24/6300's graphics hardware to make better use of early square-pixel 640×400 panels popular for Japanese and other non-IBM portables (still well suited to the basic CGA/EGA resolutions, but not so much EGA-high or MDA/EGA text, and unable to show MCGA/VGA-high or Hercules graphics without cropping or losing details) in an IBM Compatible hardware ecosystem that otherwise avoided the mode.

However, it remained on the whole a poorly supported oddity, much like IBM's own PGC and most Super EGAs outside of their limited library of applications with direct driver support, and PC graphics on the whole did not exceed 640×350 in 16 colours or 720×348 in monochrome until the arrival of both the VGA standard, and Windows 3.0 which provided a simple one-driver-for-all-programs framework for future expansion cards to build on.

The reason behind the M24/6300's failure to perform any better than equal with the 1/9th-slower Deskpro may be traceable, as hinted at in the InfoWorld review, to poorly optimised graphics routines in the BIOS, which would have a particularly noticeable effect in the high resolution 640x400 and extended colour modes.

[33] Olivetti would however be unable to repeat the feat in the subsequent years, and so 1986 represents the company's apogee in terms of PC market share.