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I've had it in my mind that each had its own "era" in a sequential thing like "CP/M was it for 8 years, and then MS-DOS was it for X years", but the early date of the IBM PC in 1981 seems to throw that idea out the window. Obviously CP/M was earlier, but how much earlier and for how long did it...

I like the name because I just think 16 sounds cool, and while I started with a VIC-20, I would have loved the 40x25 that it offered along with that 16K. Here is my real question though - WHY introduce the Commodore 16 AFTER the Commodore 64? Why not just keep selling the C64 and build new...

This is the very beginning of my Enigma M4 simulator that I want to run on the Intel 4004. For anyone with experience programming the i4004, let me know what tricks or improvements I can add to do what I am doing in a better way. The ONLY thing implemented at this time is the code that...

After some reading in the MCS programming manual I noticed that the SUB instruction is a bit odd in that it expects the carry to mean something on the way in: carry=1 means borrow occurred carry=0 means borrow did not occur but on the way out, it means the opposite! carry=1 means borrow did...

This says that KAYPRO on CP/M 2.2 returns no_error (0) on the call to F_READRAND for record 18 so long as reocrd 18 is at the end fo the file. https://github.com/ivanizag/iz-cpm/issues/6 BUT, shouldn't it fail if there is no random record there even if the random record being requested is...

http://e4004.szyc.org/emu/varia/MCS-4_Evaluation_Kit_4001_0009.pdf Any take on why address 9 contains a 254 ???

I've done some searching on the web: https://retrocomputing.stackexchange.com/questions/18224/which-endian-was-the-intel-4004 The JUN/JMS instructions store addresses high-middle-low. Also, the FIM instruction which picks up a byte from program memory (addressed as bytes) and puts the high...

I've finally got the throttling code implemented in the 4004 emulation code. I can run it throttled or unthrottled, and below is unthrottled to see how fast it _can_ run. This is on a Windows 10 box, win32 console application. My task manager says the CPU is 1.69 GHz because I have my power...

If anyone wants to look over my start to some 4004 emulation, I've attached a zip of what I've been working on the last few nights. I've tested most of the opcodes, but not all of them yet. One thing I'm still considering changing about it is that I am storing a lot of nibbles in unsigned char...

I don't see a decrement version of isz, so if I want a loop that loops 0x18 times, does it have to be done like this where I calculate the difference between 0x18 and 0x100 and increment instead with the isz instruction? Or is there a better way? The nop inside the loop is just a...

Did they use the I/O ports on ROM's / RAM's to control a serial IC ? Or a 4003? Wikipedia says about the 4003: 4003: 10-bit parallel output shift register for scanning keyboards, displays, printers, etc. But the datasheet shows parallel outputs so I'm not seeing how it would "scan a keyboard'.

The ROM's were a custom type (4001) and were mask ROM's, so did developers just build their code on paper and have a mask ROM built? Or did they have to use the 4008/4009 and use a PROM?

I've looked at the Z80 pins such as MREQ, IORQ, RD and WR and these make sense to me. http://bitsavers.trailing-edge.com/components/intel/MCS80/98-153B_Intel_8080_Microcomputer_Systems_Users_Manual_197509.pdf I'm now looking at 8080's equivalent and they are MEMR, INP, OUT, and /WO and these...

I picked up some single and double sided low density disks from a used store over the weekend for my 720K T1100 plus. Curiously, will the single sides ones work as double sided?

No video and no beeps. The voltage rails look good at 5V and 12V. The Varta battery had leaked, but I removed it and cleaned up the leaking. There wasn't too much and the traces that were leaked on look fine. I've tried the mono/cga switch in both positions. I even tried a good known CGA...

Does anyone have a list or know of a history showing which things were rolled into which NT 4.0 service packs? I know there is SP1 to SP6a I think, but when I load SP6A on limited hardware, it seems to gobble up twice the memory that a stock non-SP NT 4.0 does. I think one of the SP's also...

I have a function that returns a long which is dx:ax. I am calling DOS 42h to set/get the file position and I already have dx:ax prepared by that function call. Other functions I've done just return AX with a simple: return _AX; but when I am trying to return a long, I can't do a return...

Returned by the create 3ch or open 3df API functions. Obviously the cflag determines success or failure, but on success, is 0 a valid returned dos file handle value? If not, what isn't a valid value -1 (0xffff)?

I am trying to figure out BASM so I am making a test function, in this case a simple DOS_Open function. I've worked out how to make it work with different memory models, but the one thing I'd like to see how to do is how to get AX into the AHandle pointer. In this case my method is using mov...

I saw there were some functions in MP/M to support it. And then share.exe in DOS 3+ seemed to be where they added support for it to DOS. Why the TSR? Why not just build it into DOS? I am presuming early Netware had some sort of file locking - what DOS did that require then? 3+? Generally...