VAX 11/780 16MB memory board - what was the physical size?
I'm trying to get a feel for what it looked like when you designed a computer to have a lot of memory chips stuffed into it. To that end, I found this:...
View ArticleDid 486 SMP systems provide Total Store Ordering?
Cache-coherent SMP (symmetric, or shared-memory, multi processing) systems can provide various grades of memory ordering guarantees, the stronger ones being more expensive but making it easier to write...
View ArticleWere there any games/software that used memory beyond what was advertised...
Were there any games/software that used memory beyond what was advertised as available to BASIC on the machine ?On home / personal computers any time up to 1984 .Without needing to plug in any...
View ArticleWhat were wait-states, and why was it only an issue for PCs?
PC compatibles in the 1980s were often advertised as having zero, one, two, or sometimes more "wait states". Zero wait states was the best.Basically, the wait-states I am asking about are due to the...
View ArticleWhen did the PC bus start slowing access to video RAM?
The PC architecture, from the original IBM PC onward, has always been designed around the idea that video memory will be on an expansion card. This was an unusual design decision; most 80s computers...
View ArticleCould the Z80 do interference-free video as the 6502 could?
Technically this isn't just about video since it applies to any regularlyscheduled DMA¹ from a non-CPU subsystem, but video is the most commonapplication of this technique so I'll use that as the...
View ArticleWhy do old computers (PCs) perform a long memory test on every boot?
Basically any computers from the mid 90s and earlier perform a slow memory check on every single boot. The more memory there is present, the slower that process becomes, for example:...
View ArticleWhat are the minimum system requirements to run GW-BASIC?
In DOSBox 0.74, I can run GWBASIC.EXE without any problem (DOSBox reports 632 KB of free conventional memory). It is GW-BASIC's version 3.10 dated 01-07-1989 with filesize 72576 bytes. On screen it...
View ArticleCould today's flash memory be used instead of RAM in 1980s 8 bit machines?
I wonder if this is possible and could be a retro-project? (Not something I would try myself, though)The bandwidth of flash is surely faster than yesterday's 1980s RAM (?)Why? One possible interesting...
View ArticleWas it possible to write a novel on a BBC Micro 16kb/32kb memory era computer...
BBC Micro model B has 32k memory. An average book, like Mary Shelley's Frankenstein, has about 350,000 characters in it. So you'd need over 10 times the memory to load it in, plus the software to edit...
View ArticleWhat is “character memory” to which the VIC-II memory setup register refers?
I'm trying to understand how video memory worked on the Commodore64 in text mode. I see that the VIC-II has a memory setup register (at $D018) that keeps track of some of this information along with...
View ArticleIn a 48K Spectrum why are there 5 successive contended cycles in JR?
In a 48K Spectrum, the contention pattern for the JR instruction (see e.g. https://sinclair.wiki.zxnet.co.uk/wiki/Contended_memory) is:pc:4, pc+1:3, pc+1:1, pc+1:1, pc+1:1, pc+1:1, pc+1:1There is an...
View ArticleWhat happened to 1T-SRAM?
SRAM cells take 6 transistors per bit. A long time ago, a company called Mosys claimed they could replace this with just 1 transistor, also claiming it was as fast as true SRAM. Not only that, but...
View ArticleHow did the IBM PC handle multiple physical devices serving memory at the...
I'm trying to figure out how the IBM 5150 PC handled the case where multiple physical devices (memory chips) were mapped to the same address within the 8088's physical address space.The closest I've...
View ArticleHow much trouble was it to program segmented memory (8086)? [closed]
50 years ago, segmented memory allowed short instruction words to address high memory (above 64K) by saving the high bits of the memory address in something called the segment register.Then the short...
View ArticleWhy did programmers keep using EMS when XMS became commonly available?
I used to spend hours trying to get all of my drivers loaded in such a way that DOS games would still run. I actually managed to get a game that claimed it could not be run with DoubleSpace because of...
View ArticleWhat aspect of resetting a NES explains bits of game state being preserved?
I owned a Paperboy cartridge for the NES and something odd I noticed was that the random order of houses in the game stayed the same between pressing the Reset button, but were different when turning...
View ArticleWhich 8086 or 8088-based computer, probably made by Zenith, offered EMS...
During one of my early jobs, circa 1987, I wrote some stepper motor control and data acquisition software for an MS-DOS computer in Turbo Pascal. I'm trying to recall the computer model. I'm pretty...
View ArticleHow did MS-DOS utilities like 386MAX relocate drivers from lower 640 KB to...
You copy the driver code and data but how do you redirect everything that may have jumped into the old entry point?You could scan all the interrupt vectors and see if any of them pointed to that...
View ArticleWhere was it possible to change the value of 4? [duplicate]
I have read it in an old "hacker test" fun text, about in the middle 90s. It was about 4.Today googling refers to the idea that maybe it had been about writing into a read-only intended memory area.But...
View ArticleWhy did the NES/FC's PPU's OAM use memory that 'decays' over time?
According to the Nesdev wiki's article on the NES/FC's PPU (https://www.nesdev.org/wiki/PPU) : "while the palette is made of static memory, OAM uses dynamic memory (which will slowly decay if the PPU...
View ArticleEarliest use of SECDED memory ECC
The IBM System/370 Model 145, introduced in 1970, was one of the first mainframes to use semiconductor main memory, and instead of simple memory parity, as had been common with core memory, it used...
View ArticleWhy did BASIC programs tend to READ a redundant copy of DATA?
Take for example this BASIC version of ELIZA which starts out (in lines 50–170) by a number of READ loops which copy DATA (lines 1340 and following) into a handful of arrays.Isn't this rather wasteful...
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Why does the FRE() function in CBM BASIC v2 return negative values?
On Commodore machines featuring CBM BASIC v2, the FRE() function to query the amount of memory available to BASIC returns a negative number when the result exceeds 32767 bytes:This quirk does not exist...
View ArticleHow is the parity bit in tape storage computed?
I'm watching this video and at 5:04 it says that old cassette tape store 1 byte as 7 bit of information and a leading parity bit that could tell whether a bit of information was flipped.How was that...
View ArticleWhat was the minimum amount of addressable memory? When and why did computers...
I'm watching this video, which, at 9:51, says that around the late 1980s the majority of computers were byte-addressable.So the minimum amount of data you can retrieve from RAM was 8 bits.What was the...
View ArticleWhat's the advantage of replacing DOS/4GW with DOS/32A?
IntroductionAs far as I understand, DOS/4GW was the thing that allowed most games from MS-DOS era to access beyond the 640KB conventional memory limit. (For completeness, there was also EMS and XMS,...
View ArticleDid any computers use automatically-operated mechanical storage as...
From what I understand of ENIAC, it had a very large number of manually-operated rotary switches which behaved as ROM. While programming ENIAC in the early days required a plugboard, the machine was...
View ArticleLast computer not to use octets / 8-bit bytes
I am old enough to remember computers that were not octet oriented. E.g. the first that I used was an ICL 4120. It had 24 bit words which were, when necessary, divided into four 6-bit characters. There...
View ArticleOrigin of the rule that swap size should be 2x of the physical memory
I can trace this recommendation that swap should be twice the size of the physical memory as far back as 1989, see SunOS 4 installation manual, page 37, but I wonder if there was ever any technical...
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