The first models of ES PEVM (ES-1840, ES-1841, ES-1842), unlike the IBM PC, had two units: a system unit and a floppy drives unit. These models used a
backplane instead of the main board. Although the system bus was compatible with
ISA bus, it used a different type of connector, so the IBM PC expansion cards could not be installed in ES PEVM. Later models (ES-1843, ES-1849 etc.) were fully-compatible with IBM PC XT and IBM PC AT. Unlike IBM PC using the
Intel 8088 processor, the early ES PEVM models used
K1810VM86 processor with a
16-bit bus and a
clock frequency of 5 MHz. The processor was placed on a separate board. Early versions of the board did not have a socket for the
floating point coprocessor. The following boards were produced for ES-1840 and ES-1841: •
CPU board (containing 54 chips). It was installed in every configuration of the computer. • 128
KiB RAM board. It was installed in early models of ES PEVM. • 512 KiB RAM board (containing 110 chips). Variants with 256 KiB or 128 Kib were available. •
MDA adapter board (containing 91 chips). It was built using the
Bulgarian CM607 chip (
MC6845 clone). •
CGA adapter board (containing 94 chips). •
Floppy drive adapter board (containing 32 chips). It was built using the Bulgarian CM609 chip (Intel 8272 clone). •
Serial interface adapter board (containing 56 chips). It was electrically incompatible with the IBM PC
COM port and was not supported in the
BIOS. Volume of production for a number of models: == Software ==