Olivetti PCS 86

NEC V30 at 10 MHz with zero wait states, according to the official September 1990 Olivetti brochure; 16-bit data bus with the 8-bit ISA expansion of its XT-class architecture. The PCS 86 supports software selection between approximately 7.16 and 10 MHz, based on measurements of a physical PCS 86. Check-It 3.0 on a physical unit estimates 7.18/10.02 MHz; these support nominal 7.16/10 MHz modes, without proving the electrical clock circuit. BluMach uses 10 MHz as the primary historical profile. Its emulated slow mode targets 7.20 MHz as a slightly faster compatibility choice, not a verified physical clock.

The board provides 512 KB. Two 256 KB SIMMs complete 640 KB of conventional memory and leave 384 KB as EMS; two 1 MB SIMMs likewise complete 640 KB conventional and leave 1,920 KB as EMS. Four 16 KB windows occupy 80000h–8FFFFh.

Integrated Paradise VGA. The system BIOS also contains its initialization code, so a separate VGA option ROM at C0000h is not required.

Two interleaved EPROMs, CSAB05 (even bytes) and CSAB04 (odd bytes), form 64 KB at F0000h–FFFFFh. The set contains system BIOS, VGA, XTA and diagnostics.

Resident Diagnostics Rev. 1.09. The preserved set passes its checksum and reaches the reset vector at FFFF0h.

For compatibility, INT 15h/C0h identifies the system as IBM PS/2 Model 30, submodel 109. This is a firmware choice, not the computer's commercial identity.

Tests CPU, ROM, DMA, PIC, timer, base and expanded memory, clock/calendar, printer, communications, drives and keyboard. The observed screen is revision 1.09.

60h–6Fh: keyboard, PIT/speaker and proprietary logic. Port 65h: bit 0 XTA, bit 1 LPT, bit 2 VGA, bit 4 COM1 and bit 7 startup/test latch according to the analyzed BIOS code.

Port 60h receives keyboard scan codes and IRQ1. Ports 66h–6Ah implement the board's dual PS/2-style peripheral interface; observed IDs are AB83h for the keyboard and 00h for the mouse.

E0h–EFh: MM58167 and associated NVRAM. Commands B0h–B7h manage access and status; BIOS stores date, time and checksum in its own format.

Compatible controller at 3F0h–3F7h. The physical bank selects 360 KB, 720 KB, 1.2 MB or 1.44 MB per drive with active-low combinations.

XTA interface at 320h–323h, IRQ5 and DMA3. The historical 20 MB configuration is a Conner CP3026 (615 cylinders, 4 heads, 17 sectors).

COM1 at 3F8h on IRQ4; the real diagnostics report two communications channels, while BluMach currently models the confirmed port. LPT1 is at 378h–37Fh, including special 37Ah behavior used by resident tests.

Compatible VGA registers at 3C0h–3DFh and A0000h–BFFFFh video memory. Integrated-video selection goes through board control and VGA enable logic.

Page registers at 8400h–8403h; each selects the page for one of four 16 KB windows at 80000h–8FFFFh.

Active-low port 100h: bits 0–1 drive 0 type; bits 2–3 drive 1 type; bit 7 indicates an XTA disk. Per-drive codes are 00=360 KB, 10=1.2 MB, 01=720 KB, 11=1.44 MB. Bits 4–6 are not exposed as user options because the analyzed BIOS does not consume them.

The key/keyboard-lock state is reflected in bit 2 of port 66h.

Automatic mode derives jumpers from installed drives. Manual mode can reproduce an exact physical bank, including inconsistent settings, for research and preservation.

BIOS and MS-DOS boot; CPU, ROM, DMA, PIC, timer, 640 KB base memory, clock/calendar, printer, keyboard and EMS diagnostics. FDISK and installation of the English edition of Windows 3.0 have also been tested on a 20 MB XTA disk.

Electrical timing of the dual keyboard/mouse interface and some video-arbitration details remain functional approximations. Mapping the reported second communications channel still needs physical evidence.