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52

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 more distant ancestor that had some influence on the design of 8086, but it's not the same architecture. As an analogy, all x86 CPUs are the same genus but ...


42

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 whole motherboard), the issue is mostly the cost of support components: motherboard chipsets (whether integrated or discrete), memory, etc. By going back to a 16-...


31

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 servers on the factory floor of Digital’s plant in Scotland in 1994, and those machines were priced at around $250,000...) The Red Hill hardware guide ...


27

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 386 board from before memory modules became a thing. The mainboard can be fitted with 1 MiB using 256 KiBit chips (41256), so any expansion has to go on cards. ...


25

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 it be to use textual substitutions (e.g. macros) to automatically translate 8080 code to 8086 code, and what the limitations would be. The first point would be ...


22

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 thus more thru hole connections, but over all, doing a 32 data lines instead of 16 isn't a big deal. It wasn't the data lines themselves, but rather the ...


22

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. They are defined as follows: TR6: 31-12 11 10-9 8-7 6-5 4-1 0 Linear address Valid Dirty User/supervisor Read/write Reserved (0) Command TR7: 31-12 11 10 9-...


20

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. Although it is very unlikely, that any ordinary PC motherboard had been built with the required number of memory sockets at the time. It is more likely, that it was ...


20

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 passthrough plug and jack. I use mine with my 386 laptop.


20

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 the same micro-code as Intel’s 80386. The only speed advantages came from higher clock speeds (40MHz v. 33MHz) and, in some Am486 models, the use of write-back ...


16

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 memory (256 kBytes, but the VGA needs 32-Bit access to get the data fast enough to the screen). Those RAM chips have an access time of 100ns. The chips on your ...


16

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 must, however, first check whether the CPU is really an 80386 and not 486, because the some early steppings of the 486 temporarily re-used the opcodes of these two ...


16

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-etched number (23936). Unknown chip Am386DX-25 Source: computerbase.de via @SpehroPefhany's answer on ee.se @njuffa has pointed out that the logo laser-etched ...


15

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 CPU, all accesses must go through the PPU. This limits the extra 8 data lines and 11 address lines (for a 2 KB address space) to a small area of the board, as ...


15

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 for Weitek 3167 co-processors.) I'm not sure AMD ever produced their own 387; various on-line collections document the AMD 287, but not the 387. See here or ...


13

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 100 kb/s.


13

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 more than the six pins for Compaq-specific audio extensions. Based on a few pictures of the card, it simply routes some audio signals between card and backplane. ...


13

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 packaging for a 80386 Empty 80387 FPU socket Quadtel "386" BIOS with appropriate late-80s Copyright 50.0MHz oscillator adjacent to CPU; usually provided ...


12

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 timing. Software commands (Up for the faster 386 mode and Down for the slower speed) make speed selection simple. Initial startup via the Up command requires ...


12

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 80387 contained approximately 120,000 transistors (quite a bit more than the 8087’s 45,000 transistors).


11

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 internal clock. On the x86 FPU side of things, quite a few different companies produced FPUs: Intel of course, AMD, IIT, Cyrix, Chips & Technologies... Many ...


11

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 that either has an RS-232 serial port, or has hardware and drivers for bridging its USB port to RS-232 serial. Once the two are connected, use of the laptop as a ...


10

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 that it uses call gates.


10

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 combined with 8-bit ISA slots. The pinout is included. A single slot has the pins equivalent to two banks of (double-sided) PS/2 SIMMs. So a board with two of those ...


10

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 far from the main CPU, seen in the lower left. But without more information it's hard to say. Maybe some sharp close up can reveal markings supporting this?


10

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 detail information provided by Intel as well as reverse engineering. AMD adapted the design to their production process. This included low level changes in how ...


10

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 not about EISA) What additional signals were available in these slots? Most likely D16..31 and A24..31. Plus maybe BE0..3 - and that's where the main issue ...


9

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 PC AT 5170). And it wasn't unusual to stand a desktop cabinet on its side; this practice was common in office environments when the system unit and monitor ...


8

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 connector details here


8

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 didn't really gain traction in the PC market until version 1.1 was released in 1998. The PCI bus standard had been published in 1992, and by the mid 1990s it was ...


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