Questions tagged [performance]

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2
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1answer
119 views

How to load into FAST RAM on Apple IIgs?

The Apple IIgs (last, ROM03 version) came with 128K of standard RAM and 1M of FAST RAM. The distinguishing characteristic of the FAST RAM is that code running from there can run at 2.8 MHz instead of ...
8
votes
4answers
672 views

Does fast page mode apply to ROM?

Starting with the 4116, RAM chips from the late seventies supported fast page mode, where if you were reading nearby – particularly, successive – words, you didn't need to supply both row and column ...
8
votes
1answer
401 views

How can floating point addition be so slow on a BESM-6?

In the BESM-6 technical manuals — for example, in the ALU description, page 4 — there is a table specifying min/max/average instruction latencies in clock cycles (the last 3 columns; the ...
10
votes
4answers
653 views

For fast scrolling DOS games, when was Mode13h preferred over Mode X?

Back in the DOS days of gaming (more specifically, 80286 - 80486 era), developers typically needed to choose between using the chunky and easier Mode 13h or the more complex "Mode X" that provided ...
7
votes
1answer
277 views

Which pre-IEEE computers had a single precision FPU and implemented double precision floats in software?

Before the formats of floating point numbers have been standardized in IEEE 754 in 1985, different vendors had used many different floating point formats, some of them listed on the Data Format and ...
2
votes
2answers
290 views

FCC RF limits and wire transmission speeds

As I understand it, in the early days of personal computers, strict FCC limits on RF emissions, were a factor limiting the speed at which data could be transmitted over wires, but I'm trying to ...
1
vote
1answer
259 views

File system performance and the Unix API

A 1994 book called 'The Design and Implementation of a Log-structured file system' contains the claim "We have implemented a prototype log-structured file system called Sprite LFS; it outperforms ...
3
votes
3answers
1k views

Amiga memory bandwidth

Looking at a timing diagram for the various kinds of memory access occurring on the Amiga http://amigadev.elowar.com/read/ADCD_2.1/Hardware_Manual_guide/node02D4.html it seems to be saying that video ...
1
vote
1answer
329 views

How adequate would 48-bit floating point be? [closed]

Though power of 2 word sizes look in hindsight like a natural consensus, historical computers used quite a wide variety, including but not limited to 9, 18, 36, 12, 24 and 60 bits. Power-of-2 ...
4
votes
2answers
143 views

Can fast page mode depend on the first data retrieved?

As early as the seventies, some computers used RAM in page mode, in which you can read two or more words from sequential locations in rapid succession by only supplying the column address once, and ...
11
votes
3answers
4k views

Z80 x 6502 raw performance

A lot have been said in the internet about the 6502 at 1MHz being roughly equivalent in performance to the Z80 at 4 MHz. Is said that the Z80 have a typical 4 clock ticks per instruction while the ...
7
votes
1answer
393 views

Breakeven number of bytes for programmable DMA

Contemporary with the old 8-bit chips, existed powerful but unsung programmable DMA controllers like the Zilog 8410 and the Intel 8257, that could copy data from one memory location to another, much ...
4
votes
1answer
324 views

CPU speedup breaking sound compatibility

In the old days, it sometimes happened that a computer with a compatible but faster CPU, had problems running old games. For example, Sopwith was written for an 8088 PC; it was amusingly challenging ...
5
votes
1answer
764 views

How much faster is the Z80H?

The Z80A, rated for a maximum clock speed of 4 MHz, was a very widely used CPU in the 8-bit era. The Z80H, introduced in 1986, was rated for a maximum clock speed of 8 MHz. This would at first glance ...
8
votes
3answers
823 views

When did CPUs start using page mode DRAM?

According to https://en.wikipedia.org/wiki/Dynamic_random-access_memory#Page_mode_DRAM Page mode DRAM is a minor modification to the first-generation DRAM IC interface which improved the ...
5
votes
7answers
1k views

Benchmark between Home computers? What can be a valid parameter for that?

I'm writing my thesis about the home computer market between 1977 and 1984 (focusing on Commodore Inc.so PET, VIC-20 and 64 and competitors). I'm trying to plot a curve describing the technological ...
20
votes
4answers
3k views

Z8410 DMA chip as GPU?

There are basically two ways to design a 2D graphics system: Provide lots of hardware support in the form of tiles, hardware scrolling and sprites, to put together each frame on the fly from a small ...
11
votes
6answers
2k views

Z80 and video chip contending for random access

Back in the 8-bit days, I used 6502 computers, where the story about memory access was easy to understand. RAM chips of the late seventies and early eighties could do 2 MHz (or a bit more e.g. 2.6 in ...
16
votes
4answers
3k views

How fast is memcpy on the Z80?

I gather the fastest way to implement memcpy (copy a certain number of bytes from one place in memory to another) on the Z80 is to use an instruction called LDIR. But how fast is the result, when ...
8
votes
3answers
2k views

Floating point performance of classic minicomputers

Are there any numbers available for the floating point performance of classic minicomputers of the seventies and eighties? For example, the VAX 11/780 for integer calculations was generally rated in ...
18
votes
5answers
3k views

80s DRAM chips: one per bit of data bus width?

As I understand it, in the eighties the typical way of handling memory was one RAM chip per bit of data bus width. Suppose you were building a 16-bit machine and you wanted to give it 32K of RAM, you ...
12
votes
3answers
1k views

Speed of early ROM versus RAM chips

In the late seventies, up through around 1981, the maximum access speed of off-the-shelf RAM chips was around 2.6 MHz. Did the same speed limit apply to ROM chips of the same era? If not, what would ...
3
votes
3answers
615 views

How to compute performance of a CPU in FLOPS?

For a computer that took a variable number of clock cycles to execute floating point instructions, what would be the formula to estimate its performance in FLOPS assuming that it can execute either A ...
10
votes
2answers
691 views

When specifying Intel 80x86 instruction execution time, what is included in the cycle count?

I'm looking at this summary of the Intel x86 integer instruction set (though the same data seems to have been published in a number of places), which gives instruction timings on a per-instruction-...
13
votes
2answers
1k views

68000 and memory access speed

On the one hand, I get the impression that memory chips around 1980 could be accessed no faster than 2 MHz. On the other hand, the 68000, introduced in 1979, had a typical clock speed of 8 MHz. How ...
12
votes
6answers
2k views

Memory-limited workloads

I'm trying to figure out whether computing workloads, particularly those related to science and engineering, have historically been limited by memory or CPU. (By the former, I mean not memory access ...
12
votes
1answer
1k views

Historical cost of computing (when was $1/FLOPS crossed?)

The relevant Wikipedia page has a large gap between 1961 and 1984, not allowing to estimate, even approximately, in what year the symbolic threshold of $1/FLOPS (or, as the wiki table puts it, $1bn/...