138

Simple: Complexity. A 8088 had about 29,000 transistor functions, while an 8087 with 45,000 is almost double that. Integrating the FPU within the CPU would have made it three times as big, putting production at a >5 times higher failure rate, resulting in a price tag way higher than 3 times the CPU alone. More like 5-8 times. When closing in to what is ...


63

So these math chips (I assume you're talking about floating point units, such as the 8087 and other coprocessors) were not always/usually included in the CPU because they were not required by most users. When you don't need floating point maths, you also don't need the FPU, and that was the commonest case. So to make the CPU cheaper they leave it out. Then ...


50

Another point not addressed in the existing answers relates to the latency associated with accessing an external coprocessor. The first math coprocessors, while much faster than doing the same work on a CPU, still took many clock cycles to complete each operation. The overhead (bus cycles) associated with transferring data between the two chips was "lost in ...


38

The differences between PC floppy drives and Amiga floppy drives are as follows: PC floppy drives normally answer to drive select 1 (DS1), internal Amiga drives answer to DS0 pin 34 on the connector is used for disk change on the PC, disk ready on the Amiga pin 2 on the connector is used for high-density detection on the PC, disk change on the Amiga So ...


38

It seems to me there are a number of factors involved, some of which have been addressed in other answers: design complexity cost (which largely results from the complexity) feature necessity time-to-market Regarding complexity, as Raffzahn explains, early FPUs were much more complex than the CPUs they complemented. This meant that they needed more ...


29

No, there is no simple one-to-one mapping for the pins. (Bolded signal names will be active-low.) For example, while the 286 has two physical pins for interrupts (INTR and NMI), 68000 has three (IPL0, IPL1 and IPL2), encoding a total of 7 interrupt levels. So the interrupts are handled differently, and also the signaling for acknowledging an interrupt at ...


24

It all depends on the computer to be modified and its RAM system. For now, let's focus on the pure RAM expansion issue and drop the part about bank switching; as this is completely machine-dependent, a generalized answer, as requested, will be impossible. Even so, there are still many hurdles to overcome. One after the other: RAM Type Some machines, like ...


21

If you look into real hardware (like a Motorola/Freescale 68060, which is long out of production): Modern CPU's (mainly Intel) boosted to several GHz clock frequency have one main technical limit: How to get the heat away from the sensitive silicon. There is a lot of clever technological magic involved to do that (powering down parts of the chip not ...


18

Nothing stops anyone from creating faster accelerator cards (assuming amiga or Atari ST - the only two platforms allowing for proper expansion cards), but there would be at least 3 major things to consider: CPU's - as far as I know, the fastest "classic" 68k CPU's are about 60MHz, with some revisions that can go as fast as 80 or even 100MHz. For, say 2GHz ...


16

Most obvious question first: why not puting itn on a ISA Card and take over the bus instead? Given, there would be still some work to be done after asking for DMA and pulling /MASTER, but way less than emulating a totally different CPU protocoll. More like adapting to a weired memory subsystem. But for your points First, most obviously, they are ...


12

This simple answer is not enough room on a chip for the total transistor count given the limitations of the process technology of the day. As per Wikipedia on the Intel 8087: The 8087 was an advanced IC for its time, pushing the limits of period manufacturing technology. Initial yields were extremely low. This for the coprocessor all by itself. ...


11

Like anything else, in the end, it was "ease of use" for some value of "ease" and "use". The primary motivator was performance, the specialized processors are just an extension of the maturity of micro electronics and CPU design. Recall that the original computer were just discrete components. Then, as the ICs evolved, gates out of transistors, and flip ...


11

Memory beyond 48 KB on 8-bit Ataris is all based on bank-switching, since the 6502 processor only has 16 address lines. The CPU can address 64 KB total, and that has to include ROM and memory-mapped I/O (0xD000-0xD7FF) as well as RAM. On XL/XE Ataris, PIA Port B, at address 0xD301, is used to swap parts of physical memory in and out of various banks, so ...


10

The 4116 and 4164 have different pin allocations for the reason you'd expect: the 4164 has an additional address line (for two more bits of address in total because row and column are multiplexed). So you can't just drop one in, in place of the other. The 4116 also receives a 12v signal, which the 4164 doesn't. So you can't perform a straight substitution. ...


9

We're so used to hugely complex and dense chips these days it's easy to forget that there was a time when the 8086, with "only" 29,000 transistors (no on-chip cache of any kind), was at the edge of what could be done. To put it simply: It wasn't feasible because the chip would be too big to produce cost-effectively (die size, yield) Everything a math chip ...


8

Many small CPUs available and used today for embedded designs do not have an onboard floating point unit - most of the AVR and PIC series, MCS51, some ARM ... 8 bit single-chip microprocessors were meant at least as much, if not more, for the same market that microcontrollers and embedded CPUs target today. In that market, cost and power efficiency are ...


7

As you mentioned, you could upgrade TRS-80 Model 100's RAM to 32k. You can also get a REX chip, which uses the ROM expansion slot to provide additional flash memory. The TRS-80 Model 100 had several peripherals available (in addition to the acoustic coupler) including a cassette recorder, an external drive, a barcode reader, printers, and even a "Disk/...


7

The datasheet for that part can be found here, it lists the maximum for VBAT as 4.0 V, so yes you do need to regulate down from 5 V.


7

I haven't looked at the architectures, but I suspect that one factor will be that the architecture sometimes will have implicit assumptions about the micro-architectural implementation. To achieve a GHz clock frequency, modern processors use maybe between 8 and 15 pipeline stages - with the expectation that typically all of the stages can be in use by a ...


6

In general on old computers, the whole address space will be used in some way or other, even with less than 64 KB RAM (for ROM or I/O). So you'll have to do bank switching of some kind, or you loose the ability to use original software. That said, a common method to do RAM (or ROM) extension is "piggybacking": You solder a second RAM chip of the same type ...


6

A PC 1.44 drive, can be converted for use in an Amiga, in fact ANY Amiga can use it, but it will be limited to 880k (720k PC). The reasoning, is because PC 1.44 drive motor spins the disk at a different rate. Amiga HD (1.76MB) spins at 150RPM, where a PC drive rotates at 300RPM.


5

It's not clear from your question you're trying to do. A DS12887 "chip" has its own internal battery. It's actually not a chip, but a module containing a DS12885 chip, a crystal and a small lithium battery. The module only has one power supply connection, a +5V VCC pin and this pin must be connected to the +5V power supply during normal operation. It has no ...


5

Nothing actually prevents anybody of creating 2GHz 68060-like CPU. Or even highly-speculative out-of-order 68k-compatible one. All you need is tens (if not hundreds or more) of millions dollars to be able to spin a production process at (for example) TSMC and a talented team that would be able to create RTL for such a processor, do a proper verification for ...


5

Here (archive.org copy) is a site with specific instructions for converting PC drives from several manufacturers to Amiga replacement drives. Note that getting the disk ready signal to work is necessary for most games that didn't use AmigaDOS for floppy I/O but that accessed the floppy controller directly. These games typically waited for the disk ready ...


5

Many would agree that Motorola was in a much better position to develop their 68k into something fast and modern than Intel with their crufty x86 ;) But Motorola stopped and abandoned the 68k in favour the PowerPC (which today still is at the heart of IBM's 5+ GHz POWER CPUs). Most users of 68k CPUs switched to Intel or various RISC CPUs. Commodore and Atari ...


5

One simply did not need a math co-processor. I could do double precision floating point operations in Basic on a computer with only an 8-bit Z80 CPU (at 1.66 MHz). Yes, it was slow, but we compensated for that by writing efficient algorithms ! Later I got a 16-bit 8088 (at 8 MHz). It was only when I started using AutoCad that I felt the need for a 8087 co-...


4

Some 16K computers can be upgraded very easily, because they were designed for it. The BBC Micro Model A is one such, though you're unlikely to encounter one in original configuration any more. An additional 16KB can be added to the main RAM bank using unpopulated spaces on the motherboard, and two 16KB "sideways" slots (using banking in the $8000-$BFFF ...


4

Even if the main board does not feature place for additional memory chips, in the past it was quite possible just to solder the extra row of chips on the top of the existing ones. All power, control and data buses can be shared, often just a single chip selection pin must be bent apart and separately connected. Address resolution logic requires some tweaks ...


4

On the ZX Spectrum (at least with some versions of the logic board) you could upgrade from 16K to 48K (by installing 32 KB of memory plus a few logic chips), and IIRC you could also install 64KB and do bank switching (where the ROM and lower 16KB of RAM are fixed, and the upper 32KB are switched).


4

I may have found a possible solution. http://www.4keyboard.com/commodore/586-commodore-commodore-a500-a1200-a1200hd-non-transparent-keyboard-stickers-882798355421.html The company above sell black stickers for A1200 keyboard caps. Anyone had any experience with these?


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