GoKawiilI’ve just finished restoring one of the few computers Intel produced in the early 1990s, and I’d like to share a few pictures of this wonderful platform. It has all the ingredients to catch the eye of retro enthusiasts: a full EISA motherboard, a design that served as the reference platform for the infamous 50 MHz 486DX and the original Pentium 60 MHz, a unique chipset found nowhere else, modular CPU boards, and more. Launched in 1992 and discontinued in 1995, the Intel Xpress product line sat somewhere between the personal computer and the workstation. These were not ordinary home PCs, but modular, expandable machines built for professional and networked business use (and also built like tanks). Three versions were produced: the Xpress Desktop, the Deskside/LX (tower/server), and the Deskside/MX (tower/server with SCSI). The latter models were also rebranded by HP as part of its early NetServer line. A few months ago, I bought an Xpress Desktop from Germany in very poor condition, and it clearly deserved some love.
The motherboard and chipset
Let’s start with the motherboard. The entire Intel Xpress line was built around two main boards: the 6-slotused in the Desktop, and the larger 8-slot XBASE6TE8F for the Deskside server chassis, available in SCSI and non-SCSI versions. Here is the board that came with my Xpress system:
Fortunately, a complete parts and revision log for the Xpress series has survived, which made it possible to identify this board in more detail. The PBA 519610-004 sticker indicates that it is the 10th revision out of a total of 14, manufactured in July 1993. As expected, the motherboard is equipped with 6 EISA slots. The board is built around two distinct chipsets that divide the work between the system core and the expansion bus: Intel’s own Xpress chipset, which handles the processor, memory, cache coherency, and onboard I/O, and a separate EISA chipset, which manages communication with the EISA/ISA expansion bus.
On the Xpress side, the MECA (Memory to EISA ASIC – 82356CS) links main memory to the EISA bus, arbitrates access between the CPU and bus masters, manages memory decoding, and supports cache snooping as well as parity or ECC memory; the RCA (RAS/CAS Control ASIC – 82356DS) controls DRAM timing and addressing, generating the RAS/CAS signals and handling the multiplexed addresses for the 64-bit memory subsystem; two DPP (Data Path Parity – 82353DS) chips provide parity generation and checking for the wide DRAM data path; and the CLASIC (Common Local ASIC – 82351DS) takes care of local peripherals and system I/O, including the video controller, flash memory, EISA ID logic, and standard ports such as floppy, IDE, serial, parallel, and mouse.
Alongside it, the EISA chipset handles the expansion side of the machine: the EBC (EISA Bus Controller – 82358DT) translates CPU commands into EISA and ISA bus operations and controls bus cycles, DMA, bus-master access, and data steering; the ISP (Integrated System Peripheral – 82357) integrates core system functions such as DMA channels, timers, interrupt controllers, refresh logic, and EISA arbitration; and the EBB (EISA Bus Buffer – 82352) provides the physical buffering, latching, and parity support needed for reliable address and data transfers on the EISA bus.
The two slots on top of the EISA physically look like PCI slots, but they are dedicated to CPU and RAM daughter boards. Of course, the battery inside the original Dallas DS1287 RTC/CMOS chip was fully depleted and had to be replaced with a modern compatible DS12887+ chip. Luckily, the original Dallas chip was socketed and not soldered on the board. I added two 16 MB DIMM memory stick with ECC parity (x36 bus) as the board doesn’t accept standard 32-bit DIMMs.
CPU Boards
Up to 12 CPU boards were available for the Xpress motherboards, covering nearly the entire range of 486 and early Pentium processors: 486SX/25, SX/33, DX/33, DX/50, DX2/50, DX2/66, DX4/100, as well as the Pentium 60, 66, 90, and 100. There was even a rare dual-processor board featuring two Pentium 66 MHz CPUs in SMP, compatible only with later revisions of the 8-slot EISA motherboard. I was lucky enough to find three different boards, including the most iconic.
This EJM486CM/BXCPU486SX25 (PBA 540363-210) is the latest revision of the most affordable CPU board in the range. It comes with a low-cost 486SX/25 processor soldered directly to the board, but also includes an empty Socket 3 ZIF socket for a CPU upgrade. It can accept an OverDrive processor or virtually any 5-volt 486 up to a DX2/66. Intel fitted the board with two quartz oscillators, 25 MHz and 33 MHz, allowing a single jumper to select either one. A second jumper is used to choose between the onboard CPU and the one installed in the socket. No L2 cache is fitted as standard, but 128 KB can be added later by the user with 4x 32 KB PLL chips and 2x DIP Tag RAMs.
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