<P> A hard disk could not be installed into the 5150's system unit without changing to a higher - rated power supply (although later drives with lower power consumption have been known to work with the standard 63.5 Watt unit). The "IBM 5161 Expansion Chassis" came with its own power supply and one 10 MB hard disk and allowed the installation of a second hard disk . The system unit had five expansion slots, and the expansion unit had eight; however, one of the system unit's slots and one of the expansion unit's slots had to be occupied by the Extender Card and Receiver Card, respectively, which were needed to connect the expansion unit to the system unit and make the expansion unit's other slots available, for a total of 11 slots . A working configuration required that some of the slots be occupied by display, disk, and I / O adapters, as none of these were built into the 5150's motherboard; the only motherboard external connectors were the keyboard and cassette ports . </P> <P> The simple PC speaker sound hardware was also on board . </P> <P> The original PC's maximum memory using IBM parts was 256 kB, achievable through the installation of 64 kB on the motherboard and three 64 kB expansion cards . The processor was an Intel 8088 running at 4.77 MHz, 4 / 3 the standard NTSC color burst frequency of 315 / 88 = 3.579 54 MHz . (In early units, the Intel 8088 used was a 1978 version, later were 1978 / 81 / 2 versions of the Intel chip; second - sourced AMDs were used after 1983). Some owners replaced the 8088 with an NEC V20 for a slight increase in processing speed and support for real mode 80186 instructions . The V20 gained its speed increase through the use of a hardware multiplier which the 8088 lacked . An Intel 8087 coprocessor could also be added for hardware floating - point arithmetic . </P> <P> IBM sold the first IBM PCs in configurations with 16 or 64 kB of RAM preinstalled using either nine or thirty - six 16 - kilobit DRAM chips . (The ninth bit was used for parity checking of memory .) In November 1982, the ROM for the IBM PC was changed to allow the use of 64 Kbit chips (as opposed to the original 16 Kbit chips)--the same RAM configuration as the soon - to - be-released IBM XT. (64 kB in one bank, expandable to 256kB by populating the other 3 banks .) </P>

Which processor was released in the first ibm pc