Memory | 16 KB – 256 KB (motherboard) |
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Early revisions of the IBM PC had 16KB soldered and allowed expansion to 64KB via DIL sockets using 16Kbit RAM chips.
Later revisions featured 64KBit RAM chips, had 64KB soldered and could be expanded to 256KB on the mainboard.
The first one I used at work was already an IBM PC-XT, probably with 128KB.
I should really remember, because IBM PCs used hardware parity for RAM, which had to be initialized on a cold start. So I remember staring at the top right, where RAM was being checked and parity was initialized for quite a few seconds with RAM amount counting upward before the system would finally boot.
It also had a Hercules graphics card for 720x348 monochrome bitmapped graphics, which was the main justification for the purchase of that system over using time shared mainframes.
Of course it had this giant 5 1/4" 10MB full height hard disk, which was still called a "Winchester Drive" and it ran PC-DOS 2.0 with subdirectories to manage it.
I ran quite a few variants of CP/M on my own Z-80A and Z-80B systems at home before and during that time until I could afford an 80286.
I don't know where I got the CP/M 2.2 -3.0 assembly source code, but I did have it and read it "cover-to-cover" at the time. Just like Unix v6, written in C, where we went through the full source code at university.