56
votes
Accepted
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 ...
- 3,567
43
votes
Accepted
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 ...
- 131k
37
votes
Accepted
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 ...
- 131k
32
votes
Accepted
How can a 32-bit x86 CPU start with reset vector 0xFFFFFFF0 even though it starts in 16-bit real mode?
When x86 boots, it's not strictly in classic real mode, it's in "unreal" mode, with CS.base = 0xFFFF0000 and CS.limit = 64K.
On 286 and later, memory addressing doesn't use the segment ...
- 3,567
30
votes
Accepted
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 ...
- 236k
28
votes
Accepted
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. ...
- 131k
25
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. ...
- 1,778
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 ...
- 13k
25
votes
Accepted
When did the 386 overtake the 286?
According to Dataquest’s 1992 “Microcomponents Worldwide” report, shipments of 386 CPUs overtook shipments of 286 CPUs in 1991; in thousands of units shipped:
Processor
1990
1991
88/86 Subtotal
21,...
- 131k
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 ...
- 236k
21
votes
Accepted
What is the oldest free Assembler targeting the 386 CPU
The Netwide Assembler (NASM) was first released in October 1996. From the beginning it supported Intel syntax (similar to MASM and TASM) and most if not all known x86 instructions, and could be used ...
- 131k
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 ...
- 4,860
20
votes
Accepted
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 ...
- 131k
19
votes
Why did Steve Jobs choose the Motorola 68030@25 MHz for the first NeXT Computer in 1988 and not an Intel 80386DX@25 MHz processor?
As far as I can tell almost nobody except the PC makers used x86. 68k was the more common architecture by far being in the Sharp 68k, Amiga, Macintosh, Megadrive, Sun-1, Vaxstation 100, and SGI Iris. ...
- 714
18
votes
Accepted
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 ...
- 37k
18
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-...
- 9,460
18
votes
How can a 32-bit x86 CPU start with reset vector 0xFFFFFFF0 even though it starts in 16-bit real mode?
To understand this, you need to understand the basics of segment:offset addressing in protected mode: the segment value points to a descriptor, which contains a base address, segment limit and various ...
- 131k
16
votes
Accepted
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 ...
- 8,311
16
votes
How do I best simulate a 80386?
I don’t know about “best”, but Bochs includes a good debugger; here’s its most basic UI:
Other UI variants exist.
Note that Bochs emulates a Pentium MMX or later; it can’t be configured to ...
- 131k
16
votes
Accepted
Why did Steve Jobs choose the Motorola 68030@25 MHz for the first NeXT Computer in 1988 and not an Intel 80386DX@25 MHz processor?
Very likely, familiarity with the Motorola environment and Motorola as a supplier within the development staff might have been technical reasons for choosing that CPU. After all, quite some of the ...
- 37k
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 ...
- 14.1k
15
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 ...
- 37.2k
15
votes
Accepted
Does Intel Inboard 386/PC work on XT clone systems?
In the 1980s, there were dozens, if not hundreds, of companies making PC clones. Some used very careful and detailed engineering practices which systematically ensured that they would abide various ...
- 39.2k
15
votes
Accepted
What 386-specific features did Linux use?
One of Linus’ other posts provides the answer:
PS. Yes - it's free of any minix code, and it has a multi-threaded fs. It is NOT protable (uses 386 task switching etc), and it probably never will ...
- 131k
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 ...
- 691
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 ...
- 61.5k
12
votes
Accepted
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 ...
- 131k
11
votes
Accepted
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 ...
- 131k
11
votes
Accepted
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 ...
- 14.2k
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 ...
- 61.5k
Only top scored, non community-wiki answers of a minimum length are eligible