All Questions

Filter by
Sorted by
Tagged with
12
votes
4answers
1k views

C64 BASIC: How to suppress the '?' sign when using the INPUT command?

When you are getting INPUT in Commodore BASIC it always adds a question mark at the end of the string you want to show. Is there a way to suppress the question mark when using the INPUT command?
13
votes
4answers
1k views

6502: What does the Predecode Register exactly do?

When you look at this block diagram you can see a 'Predecode Register' I suppose that the Opcode is already a 8-bit Number (D0-D7). So what was the purpose of the Predecode Register. Did it really ...
4
votes
1answer
393 views

Anyone know the specific differences between a Northgate Omnikey 101 and 102?

Quick background-- I really love old school springy/mechanical keyboards. I haven't used one in years but it's been on my "to purchase" list for years to get an IBM Model-M for my work. After doing ...
5
votes
1answer
388 views

Cost differential between 2 and 4 MHz RAM chips in 1982

The most common speed of the 6502 was 1 MHz, allowing the use of 2 MHz RAM chips (half the bandwidth went to the video chip to refresh the screen). In 1982, the BBC Micro shipped, with double speeds ...
10
votes
10answers
2k views

Which pointing devices were used by early laptop computers?

I've started reading this article on the history of the ThinkPad. In it, the TrackPoint (pointing stick/"nipple" mouse) is heralded as an important innovation in the design of portable computers at ...
8
votes
1answer
232 views

QEMU with SunOS 4 - how to transfer files

How do I transfer files between the host and the guest when using SunOS 4 under QEMU? I have followed this guide: https://en.wikibooks.org/wiki/QEMU/SunOS_4.1.4 But when I try to rlogin or rcp, I get ...
21
votes
4answers
4k views

Z8410 DMA chip as GPU?

There are basically two ways to design a 2D graphics system: Provide lots of hardware support in the form of tiles, hardware scrolling and sprites, to put together each frame on the fly from a small ...
8
votes
1answer
418 views

How can I tell if an Apple II disk image is bootable?

I have around 500 floppy disk images from an Apple II and IIgs BBS/usergroup that closed down recently. Some of the disks are bootable, but many aren't. Is there an easy way to tell if a disk boots ...
11
votes
6answers
2k views

Z80 and video chip contending for random access

Back in the 8-bit days, I used 6502 computers, where the story about memory access was easy to understand. RAM chips of the late seventies and early eighties could do 2 MHz (or a bit more e.g. 2.6 in ...
10
votes
2answers
605 views

Why does this BASIC program keep restarting?

Here is a BASIC program for the Commodore 64, which should load the LIB file from the disk, and then stop. Yes? 5 PRINT "LOADING..." 10 LOAD "LIB",8,1 20 STOP the LIB file is 102 bytes long and is ...
4
votes
4answers
653 views

RAM contention and what counts as different banks

From https://en.wikipedia.org/wiki/ZX_Spectrum_Contended_Memory "Contended memory space, on the other hand, is shared between the ULA and the Z80 and the ULA has higher priority. Contended memory ...
5
votes
1answer
251 views

Collection of older EPROM IC's

I acquired a collection of older EPROM IC's and am wondering what the rarity of them are or if they are rather common. Do people collect these items? 89142 NM27C512Q ~~ B9212 NM27C512Q ~~ B9312 ...
7
votes
2answers
1k views

C64: Strange Behaviour on Control Port 1

I wrote this little Basic program to get Joystick input from Control Port 1. I know that this method is very strange and is better for keyboard input. 20 get a$ 30 if a$="" then 20 32 b=asc(a$) 33 ...
9
votes
4answers
844 views

Video chip for hypothetical 1988 arcade game

I have a project where I aim to create a retro arcade game cabinet, the technology would be ~1988. For now I am planning to only simulate the system on my PC in order to develop the game. The ...
8
votes
1answer
422 views

Is it possible to chain TMS9918 chips to get better graphics?

I'm considering creating a retro system but without requiring the sacrifice of any retro machine in order to get parts. The TMS9918 chip seems the only "generic" retro graphic chip, all other chips ...
5
votes
2answers
811 views

How hard would it be to port Amiga OS4 to x86 or ARM?

This question was raised on Facebook a few hours ago. Some say it's possible, others say impossible. What do you experts say?
5
votes
1answer
424 views

What is the title of this Macintosh programming book?

Back when Mac OS was called "System" and preemptive multitasking was a distant fantasy, I had a small collection of Macintosh programming books. For the life of me, though, I can't remember what one ...
14
votes
1answer
537 views

Where are the blueprints of MOS chips?

Atari historians have been able to find documents and tapes of chips and hardware developed at Atari. E.g. http://atariage.com/forums/topic/154479-new-gtia-chips/ . Nothing like this is happening ...
29
votes
2answers
3k views

C64: Why is POS(π) faster than POS(0)?

According to this article: german C64 Wiki article about the POS() command POS(π) is 20 % faster. Although in my experience it is ...
12
votes
2answers
961 views

PET space arcade game with surprisingly good graphics

We had PET computers in my high school, 4032's IIRC, and a few classic games to go with them - the excellent Space Invaders port, Star Trek of course, and a few others. These all used PETASCII for ...
9
votes
1answer
1k views

What is this extra lead in my monitor cable?

I have a breadbox Commodore 64 with a Commodore 1702 monitor. My monitor has three RCA-style inputs on the back: Audio (White) Luma (Yellow) Chroma (Red) I purchased a cable which claims to be an ...
4
votes
1answer
238 views

Primary manufacturers of picture tubes for early monitors

Which companies were the most important manufacturers of picture tubes for monitors (both monochrome and color) in the seventies and eighties? That is, it's easy enough to find lists of monitors by ...
5
votes
1answer
287 views

Cyrillic Ж on IBM 1620?

Wikipedia says that The IBM 1620 Model I used the Cyrillic character Ж (pronounced zh) on the typewriter as a general purpose invalid character with correct parity. The Model II used a new ...
7
votes
6answers
2k views

How can I copy files from a Compaq Deskpro?

I have a Compaq Deskpro EN 6266 Deskpro EN PII 266 Computer, pictured below. When I try to insert a 4.7 GB optical disk, the PC stops. When I use a 720MB optical disk it says that I don't have ...
4
votes
1answer
298 views

Need help identifying an Apple IIc game/possibly educational with a top-down view

Played it around the end of the 80's but most probably developed between 1981 and 1986. You had control over a person/avatar (not stick figure like, more plump looking) and could walk from scene to ...
4
votes
2answers
260 views

Getting a disk image off of a HP 9133 drive

I have a HP 9133 combo disk drive connected to an HP 9000 model 310 computer running Basic 4.0. This setup is used to control a few machines, and does not have a floppy inserted. The hard drive is ...
9
votes
3answers
1k views

Game cartridges on the S-100 bus?

Many Z80 computers in the seventies and early eighties used the S-100 bus, into which you could plug many kinds of expansion cards. Would it have been possible to plug suitably designed game ...
7
votes
1answer
227 views

Was there an interactive macro/scripting language named PAGEN?

In a BESM-6 disk image I can see bits and pieces of something that looks like a strange interactive scripting language: [start of disk block] <LET=P11=%X01 <IEQ=P11=%377 <LET=P11=1 <END &...
3
votes
2answers
432 views

C64, basic v2, DATA strange behavior

I have the following code line: 0DATA"-+-+-" Here "\" and "/" are the ASC codes 205 and 206. I get a syntax error: ?SYNTAX ERROR IN 0 READY. As I can remember, there was same special in the ...
8
votes
2answers
1k views

Can the ADB keyboard and mouse be converted to the 128K Macintosh?

As you probably know, the original Macintosh 128K, 512K (Fat Mac) and the Macintosh Plus (IIRC) have a different keyboard and mouse connection than the later ADB versions such as the Macintosh SE ...
17
votes
4answers
3k views

How fast is memcpy on the Z80?

I gather the fastest way to implement memcpy (copy a certain number of bytes from one place in memory to another) on the Z80 is to use an instruction called LDIR. But how fast is the result, when ...
8
votes
3answers
407 views

Copying disk image from HP 9122D drive

I have a HP 9122D (EDIT: its actually a 9133) combo disk drive connected to an HP 9000 model 310 computer running Basic 4.0. This setup is used to control a few machines. The hard drive is getting ...
8
votes
2answers
944 views

What was the first commercially available computer with ECC memory?

In the early days of computing, memory error detection and correction was either non-existent (Wikipedia tells of Seymour Cray famously saying "parity is for farmers" when asked why he left it out of ...
18
votes
2answers
2k views

How did Z80 multiprocessing work in the Namco Galaga hardware?

Galaga was a popular arcade game developed and released by Namco (Midway in N. America) in 1981. It had amazing, fast, smooth 2D-sprite graphics, and relied on Namco hardware that utilized 3 Z80 CPUs ...
7
votes
3answers
769 views

Serial Receipt Printer Garbage

I connected a vintage serial matrix receipt printer (Datamega DPN-233) via FTDI to my MacBook's USB. It performs its own self-test without problems, prints an example and the RS 232 configuration (...
8
votes
3answers
2k views

Floating point performance of classic minicomputers

Are there any numbers available for the floating point performance of classic minicomputers of the seventies and eighties? For example, the VAX 11/780 for integer calculations was generally rated in ...
2
votes
1answer
334 views

What Apple computers are shown in this MacBook Pro Reveal video?

In this Reveal video for the new MacBook Pro, seven or eight vintage Apple products are shown. Which ones exactly are they? The other question similar to this one is asking about a completely ...
2
votes
2answers
416 views

What typewriters and computers are shown in this commercial?

In this Apple commercial for the new MacBook Pro, there are several typewriters as well as a few retro Apple laptops shown. Which typewriters and laptops are being shown? Screenshots Order is left ...
10
votes
6answers
2k views

Sound chips in 1977

By the early eighties, there were a variety of off-the-shelf sound chips suitable for use in home computers and arcade games. What about 1977? That seems to have been just a little early; I'm not ...
8
votes
5answers
628 views

Why isn't the approach to lower power CPUs guided by design rather than accident?

We know that the ARM chip came out of the Acorn computing initiative. In the book The One Device, we read: The low-power big thing that the ARM is most valued for today, the reason that it's on ...
5
votes
2answers
865 views

Are there any articles elucidating the history of the POPCOUNT instruction?

Figuring out how many bits in a group of bits are set to 1, known as computing "population count", Hamming weight, or "bit summation", among others, has various applications. It is also fairly cheap ...
13
votes
11answers
3k views

Commercially available computer with single-step feature?

Was there ever a commercially available hobbyist/teaching computer with the ability to single-step the processor? Maybe a Z80-based machine?
19
votes
2answers
1k views

Slash versus backslash as directory separator - what/who caused this rift?

MS DOS and derived systems use backslash \ for path separator and slash '/' for command parameters. Unix and a number of other systems used slash '/' for paths and backslash \ for escaping special ...
17
votes
5answers
3k views

Why does the Z80 have a half-carry bit?

The Z80 apparently had a 4-bit ALU, and computes 8-bit values in two stages. The half-carry bit preserves the carry from bits 3 to 4. Why did the designers of this chip choose to preserve that value ...
17
votes
3answers
1k views

Obscure uses of the Commodore 8050/1541 disk drive

When I was working for a foundry consultancy, we did the following Download routines to add delays when writing certain tracks. This was a security feature. When the program started, it would try ...
10
votes
1answer
998 views

Where do command line switches originate from?

In Linux we have command line switches traditionally started with minus ls -al. In Windows those start with slash dir /b. I remember that on RSX-11M that I used to deal with and later on RT-11 the ...
3
votes
1answer
197 views

Simulate Repeat/Until in BASIC, and on a single line?

Is there a way to simulate a Repeat/Until loop in a BASIC language without it, and without using a GOTO statement? For BASIC languages with command separators, can this be done on a single line ...
3
votes
2answers
445 views

How could a 16-sector PROM Apple II access a 13-sector disk?

When the Disk ][ first came out for the Apple II, the PROMs on the interface card only knew how to work with a 13-sector format. Around 1980, the Disk ][ was updated with 16-sector PROMs either for ...
4
votes
2answers
931 views

How does the Apple II address more than 128KB of RAM?

For the Apple //e, it was very common to have an extended 80-column card installed which brought the machine up to 128KB of RAM via 2 banks of 64KB each. There are soft switches in the $C0xx space ...
33
votes
5answers
4k views

Executable ASCII files before x86?

I've known about a technique allowing to bootstrap arbitrary 16-bit x86 code from a subset of instructions representable as printable ASCII bytes since the early 1990s. The first example of an ASCII ...

15 30 50 per page