New answers tagged ibm-pc
5
It's not a completely robust answer, but I found the following text archived at Computer Business Review from March 1987 that's primarily about Zenith's plans:
In the UK, 27% of Compaq’s revenue comes from its 80386
The Compaq Deskpro had originally been announced only six months before that article, in September 1986.
So based on the timeline:
a 386 was ...
3
You question says that the UK computers were produced only to fill 'a niche' left by the U.S. computers but that's not the case. These were large, wide-open markets at that time.
The BBC micro, for instance, was a attractive product with better capabilities than the Apple II: faster, better screen modes, better BASIC, better OS.
The ZX80 and particularly ...
3
Per the Personal Systems Reference IBM PC 1994 to 2000 (PDF) it appears the default was the Standard 101 keyboard (rubber dome) with optional upgrade to an Enhanced 101 key (Model M) or Enhanced 101 key with TrackPoint II (Model M13) up until the Pentium 60 model, with only the Standard 101 rubber dome after that until it was replaced with the Standard 104 ...
8
While it's hard to come by numbers, there are several non clone candidates that sold quite well:
Sirius 1/Victor 9000 1981-1984- Outsold the IBM-PC in Europe by far not at least due better hardware and a headstart of almost a year. It got screwed by company politics in the US ignoring the European success.
Sanyo MBC-550 1982-1986
Siemens PC-D 1982-1986
NEC ...
5
Stephens Answer points out most details, I belive it's worth to mention that the 80186 is not incompatible with the IBM-PC's structure/hardware per se. The CPU core works for all details like a 286 in real mode, with the same additional instructions and exceptions, as there are:
Instructions:
Array Check (BOUND)
Integer Multiplication Immediate 8/16 (IMUL)
...
21
Short answer: If you are content with beeps, no. If you want arbitrary sound, yes.
There's three ways to get sound out of the PC Speaker:
Put the timer chip into square wave mode and send frequencies (actually countdowns) to the timer chip. This is cheap and what's used for most PC Speaker sound effects in games. 140Hz is a popular rate to do it at.
Set up ...
11
The synchronization is possible via polling, but it could also be done by interrupt even when no hardware interrupts were provided. It worked on any card that had a "real-time" status register with relevant information. I did that many times along the years, even as late as mid-90s. The trick? Take over the timer interrupt, and use it for two ...
1
If video was 1st, then printing was a close behind 2nd.
Applications needed their own printer drivers to format the application's data for printout, in a language that the printer could understand. There were several families of printers, each family's language somewhat compatible within that family (often with caveats and incompatibilities). Yet many ...
16
It is possible to synchronise with vertical blank, but it involves polling (as does avoiding snow on CGA). Two bits are important in the status register, read from 0x03DA:
bit 0 is 1 when the CPU can touch the CGA buffer without causing snow;
bit 3 is 1 during vertical retrace.
So a change in bit 3 from 0 to 1 would signal the start of a vertical blank.
19
That paragraph should be understood in the context of the preceding paragraph:
The PC speaker was often used in very innovative ways to create the impression of polyphonic music or sound effects within computer games of its era
Effects such as those used in Pinball Fantasies in particular involve very rapid changes to the sound output by the PC speaker, ...
31
The main issue with the 80186 isn’t with the CPU core itself, but with its integrated peripherals: they aren’t compatible with those used in the IBM PC, and they aren’t integrated in the same way either.
The IBM PC uses an 8237 DMA controller at offset 0x00 in the I/O address space, an 8259 PIC at offset 0x20, and an 8253 PIT at offset 0x40. The 80186’s ...
9
Yes, the sector size is software-controlled, to a certain extent. Every FDC command involving sectors or tracks takes the sector size as a parameter. The size is specified as a bit shift applied to 128, so sector sizes are of the form 128 × 2n (usable values go from 128 to 4096 on the original PC; there isn’t enough time to fit an 8KiB sector in a track ...
13
But was there anything other than video that was a source of hardware compatibility issues in the first wave? Or put another way: after video, what was the second most common source of compatibility issues for the semi-compatible DOS machines of the first wave?
On the software side I'd say sound may lead a tiny bit before any other hardware device - then ...
10
Aspects I recall, perhaps influenced by the area I was working in at the time:
Video display (as you mention)
Serial ports
Timer interrupt
I only had to work with "near-compatible" machines a few times before everything went to "100% compatible" for most hardware interfaces.
20
How interchangeable was PC BIOS?
Usually not interchangeable at all. Keep in mind, there is no single PC-BIOS, but a machine BIOS. Different CPUs, chips sets and additional hardware need specific initialisation. And, at least for generic DOS, specific drivers.
To start with, plug-in-compatible bios was only a thing for 100% hardware clones, something only ...
21
No reason to expect it works at all.
So if the CPU can even start executing the code, the moment where it goes wrong is when there are instructions for a newer CPU, or some chipset-specific initializations are done.
The BIOS is tailored for the specific motherboard, which will have a certain chipset for a certain CPU class, and therefore it also expects ...
5
How did the parity check DRAM chips work?
They are standard 4116 like their brothers. No special workings here.
Parity check itself was done by the same chip as used for parity generation, a 74LS280 (U94), and signalled as NMI with reason on bit 7 (80h) of port 62h, which is port C of the 8255 in U36.
In particular, is there a reason for the gap in the ...
13
The year you've picked has a strong influence on the answer. By 1999, most new games were being released to run under 32-bit Windows using DirectX, and were therefore running in a demand-paged multitasking virtual memory system. This has two consequences:
Checking available memory was no longer necessary - if you didn't have enough, the OS would emulate it ...
10
Although it was possible to customize MS-DOS to use machine-specific services, the actually shipping generic versions did need an IBM-compatible BIOS so you will need to provide it if you want to run unmodified DOS distributions.
In addition, various programs running on top of DOS did use additional BIOS services (when they didn’t access hardware directly). ...
21
TL;DR:
It all boils down to the question if you want to build a fully IBM like system with ROM BIOS independent of DOS, with all the bells and whistles attached, or if your goal can be reached with a running DOS with a minimum in BIOS compatibility, just enough to serve whatever application need to run on top of DOS.
Unlike often assumed, MS-DOS does neither ...
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