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The start of x86: Intel 8080 vs Intel 8086?

8086 was designed to make asm source porting from 8080 easy (not the other direction). It is not binary compatible with 8080, and not source-compatible either. 8080 is not an x86 CPU. 8080 is a ...
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42 votes
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386SX, NES and how much did data lines really cost anyway?

The situation with the 386(DX) v. 386SX is similar to the situation with the 8086 v. 8088. The big issue isn’t the data lines (although they do have an impact on complexity and cost when routing a ...
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32 votes
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How much RAM could one put in a typical 80386 setup?

I very much doubt that anyone would ever have seriously considered fitting 4 GiB in a 386-based system, let alone designing such a beast. (To put this into context, I remember seeing early 1 GiB Alpha ...
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27 votes
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What are these weird long ISA slots on this 386 board? (not VLB)

I found this page on the motherboard, which says they are some sort of "32-bit external memory card." What are these slots? They are exactly that, memory expansion. This is a rather early ...
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25 votes

The start of x86: Intel 8080 vs Intel 8086?

To supplement @PeterCordes's excellent answer, I thought it would be worth going into the details of exactly how close to source code compatible the two processors are -- for example, how easy would ...
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22 votes

386SX, NES and how much did data lines really cost anyway?

So that indicates extra data lines were very expensive; the difference between a 386SX and 386DX computer came to hundreds of dollars. Not really. Sure, they need to have some room and routing - and ...
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22 votes
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How were the test registers used on the i386 and the i486?

The 486 test registers are described in the i486 Processor Programmer’s Reference Manual, starting on page 10-8. The 386 test registers are a subset. Registers TR6 and TR7 provide access to the TLB. ...
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20 votes

How much RAM could one put in a typical 80386 setup?

We can see the datasheet of the 386DX here. The most important part is its pinout. We have address lines from A2 to A31. It means, that yes, it could have handled 4GB memory on a motherboard. ...
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20 votes

Connect Ethernet via Parallel or Serial in old laptop

Yes. For example, the Xircom PE3-10BT is a parallel port adapter that allows an RJ45 connector be plugged into it. You don't get full 10 Mbps with it, but it works. Mine is powered via a PS/2 port ...
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20 votes
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How did AMD's 386 and 486 perform like Intel's newer generation?

The Am386 and Am486 were designed as clock-for-clock equivalents of the corresponding Intel CPUs, based on reverse-engineering and AMD’s previous second-source licenses — at least the Am386 even used ...
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17 votes

Identifying motherboard and CPU

I inquired about the CPU over on ee.se. The chip appears to be an AMD Am386DX-25. Compare the lower printed number (107M7NX and 107M7NZ), the fonts used, the logo at the bottom-right, and the laser-...
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16 votes
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Is solder-on memory upgrade an option here and how to check it

The daughterboard is the graphics card. The GD610/GD620 is a quite common chipset for LCD/VGA graphics in laptops. It uses two 64k x 16Bit RAM chips to obtain 64k x 32Bit, which is the usual VGA ...
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16 votes
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Intel 386 multiply bug

Software can identify those early steppings on the 386 by checking whether the XBTS and/or IBTS instruction can be executed, since these instructions were dropped in later chip revisions. Software ...
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15 votes

386SX, NES and how much did data lines really cost anyway?

It's not just how many data lines, but where you have to route them. While the PPU on the NES does have its own independent RAM, it is connected only to the PPU. To update the tile RAM from the main ...
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15 votes
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Pair Am386 with i387

The Intel 387 should work fine with an AMD 386DX; the latter was a direct clone of the Intel 386. The extra rows of pins are perfectly normal — see this photo for an example. (The extra pins were used ...
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13 votes

Connect Ethernet via Parallel or Serial in old laptop

If you have another computer to hook it up to and act as a bridge (or router), you could in principle run SLIP or PPP over the serial port to another machine. You're unlikely to get speeds exceeding ...
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13 votes

What was the "32-bit" ISA bus (connector) extension for 80386 PCs?

No, this sound card is definitely not intended for such a slot that expands the ISA slot to 32 bits. This is a Compaq-specific sound card meant for a Compaq-specific ISA slot extension. There is no ...
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13 votes

Identifying motherboard and CPU

Apart from the unrecognized branding on the CPU (ceramic; upper-right in photo) chip, this appears to be a bog standard ISA '386 motherboard, probably running at 25 MHz. CPU looks like the right ...
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12 votes
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What exactly were those 808X computers that would switch to 80386 upon Ctrl-Alt-Del?

What you describe sounds like the PC Elevator: The PC Elevator 386 is a coprocessor-type accelerator board. The system's native CPU remains available for any programs that are sensitive to speed or ...
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12 votes
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80387 transistor count

I’ve wondered about this for a long time — manufacturers don’t seem to communicate FPU transistor counts as readily as CPU counts. The best I’ve found so far is a claim on coprocessor.info that the ...
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11 votes
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What was the fastest third party FPU?

I don’t recall SPARC systems having separate sockets for discrete FPUs; in particular, the Weitek SPARC POWER µP was a replacement SPARC CPU which derived much of its speed benefit from doubling its ...
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11 votes

Connect Ethernet via Parallel or Serial in old laptop

Since it's a pretty early laptop without a PCMCIA port, there won't be a way to add an Ethernet port. Your best approach is to use the serial port to connect via null-modem cable to a modern machine ...
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  • 56.8k
10 votes

Examples of operating systems using hardware task switching of x86 CPUs

iRMX III is a real-time operating system for Intel 80386 and later processors, originally developed by Intel and now maintained by tenAsys. A quick look at the System Call Reference manual reveals ...
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10 votes

What are these weird long ISA slots on this 386 board? (not VLB)

Photos of the manual of (nearly) that board appeared on the VOGONs forum in https://www.vogons.org/viewtopic.php?p=844188#p844188 . They clearly spell out that these slots are 32-bit memory slots ...
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10 votes
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What is this socket for in 386 notebook motherboard

Well, it could easy be a socket for a 387 type FPU. Size and number of pins would fit a 387 (or some pin compatible Cyrix FastMath) as PLCC carrier. On the other hand it's rather unusual to place it ...
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10 votes

How did AMD's 386 and 486 perform like Intel's newer generation?

Is it really so simple as just getting to higher clock speeds than Intel did? Yes, it is that simple. Up and including the 486 AMD's CPUs were developed close to Intels devices, supported by in ...
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10 votes
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What was the "32-bit" ISA bus (connector) extension for 80386 PCs?

Were those slots manufacturer-specific or was there some kind of (unofficial) standard? Manufacturer specific. (Well, there was EISA, but I guess it's safe to assume that this question is explicitly ...
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9 votes
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When did the tower form factor appear and when did it become popular?

The tower form factor was well known in the 1980's, even IBM was using it at that time (the IBM RT 6150 was available in both desktop and tower cabinets, and IBM even had a tower stand option for the ...
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8 votes
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What make and model is this 386 mainboard?

This is my best guess, but it looks really close. Could it be a Gigabyte GA-386PS? This block diagram looks very similar: I couldn't find the actual manual, but there are some jumper setting and ...
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  • 8,436
8 votes

USB ports for a 486 laptop (pccard 16bits)

The laptop you describe is unlikely to be able to support USB ports, for hardware reasons. But there may be an alternative solution. The first USB standard (version 1.0) was published in 1996, but ...
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