Why does my Epson HX-20 apparently have much less RAM than expected?
When I enter:STAT ALLOn my Epson HX-20, I get the following output:P1: 419 BytesP2: 86 BytesP3: 0 BytesP4: 0 BytesP5: 0 BytesRAM FILE 256 BytesMEMSET 2624 105 Bytes FreeAs I understand it, even a...
View ArticleWhen did CPUs start using page mode DRAM?
According to https://en.wikipedia.org/wiki/Dynamic_random-access_memory#Page_mode_DRAMPage mode DRAM is a minor modification to the first-generation DRAM IC interface which improved the performance of...
View ArticleHow does the Apple II address more than 128KB of RAM?
For the Apple //e, it was very common to have an extended 80-column card installed which brought the machine up to 128KB of RAM via 2 banks of 64KB each. There are soft switches in the $C0xx space...
View ArticleWhat is the motherboard part number for the Macintosh IIci that required...
This is an extension of an answer I posted years ago to the Retrocomputing question:How did Apple fail to tap the business and scientific markets?Most (all?) IBM PC systems required parity memory, but...
View ArticleWhere are the memory controllers for IBM 5150 or Altair 8800?
Wikipedia page for memory controller states that memory controllers are either part of the northbridge, or in more recent cases, integrated into the processor.But AFAIK, neither IBM 5150 nor Altair...
View ArticleWhat did it cost the 8086 to support unaligned access?
The Intel 8086 supported unaligned loads and stores of 16-bit data, e.g. mov ax, foo was guaranteed to work even if foo was odd.What did this cost, in terms of performance and chip area, compared to an...
View ArticleHow did the IBM 360 detect memory errors?
What logic did the IBM 360 use to detect, and perhaps correct, memory bit errors?
View ArticleWas it possible to give an Atari 800 (not XL) 64KB of RAM?
The original Atari 800 could have up to 48K of RAM installed through the use of memory cards. When the 800XL came out, it was now possible to have up to 64K of RAM by disabling the BASIC ROM.After...
View ArticleHow did the Fairchild Channel F provide a 2K frame buffer?
The Fairchild Channel F, released in 1976, was the first modern game console, in the sense of being the first one to accept games as software, rather than just modular configuration switches.Looking at...
View ArticleDid the Vic-20 save money using static RAM?
The unexpanded Vic-20 had 5K of RAM. This was quite small even by 1981 standards, but it was trying to be cheap enough for consumers to buy, and it succeeded, selling over 2 million units.One reason...
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Simple doubling of ZX80 RAM
Many moons ago when I owned a ZX80, I remember (or possibly mis-remember) seeing a simple way to double the RAM to 2K by simply piggy-backing two extra 1Kx4 chips on top of the existing two (with...
View ArticleDid anyone ever run out of stack space on the 6502?
Unlike its main rival the Z80, the 6502 had a size limit of 256 bytes for the hardware stack. That sounds like a very tight limit, but in my experience, it was never actually an issue; by the time you...
View ArticleWhy did the Cray-1 have 8 parity bits per word?
According to https://en.wikipedia.org/wiki/Cray-1The Cray-1 was built as a 64-bit system, a departure from the 7600/6600, which were 60-bit machines (a change was also planned for the 8600). Addressing...
View ArticleCould the Apple IIGS play any and all Amiga MOD files?
The Apple IIGS has a wavetable synthesis sound chip with dedicated 64 kilobytes of RAM.I assume the sound architecture dictates that samples have to be loaded into that dedicated RAM to be able to be...
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...
View ArticleHow much memory did the PlayStation development kit have?
The PlayStation 1 had two megabytes of main memory, one megabyte of video memory and half a megabyte of audio memory. Squeezing everything to fit into these limits was one of the big challenges of...
View ArticleHow to use all memory on an IBM PC with 8086
I'm developing software for the IBM PC with an 8086 processor. I want my program to use all available memory.I know that I can use DOS int 21h function AH=48h to allocate all available conventional...
View ArticleDid any 8-bit computers use 16kx4 RAM chips?
An 8-bit computer wanting 64K of RAM, could most straightforwardly use eight 64kx1 DRAM chips (64kbit, 1 data line). The Commodore 64 initially did this, but in the mid-80s, the cost-reduced redesign...
View ArticleDid DOS zero out the BSS area when it loaded a program?
As an example, say we have a DOS MZ EXE file that's around 20 KiB in size. The EXE header contains the value 0x1400 at offset 0x0A indicating that the program is requesting 5,120 paragraphs (or 80 KiB)...
View ArticleHow did the X-Men game for Sega Genesis have its state survive a console reset?
The Sega Genesis system had a rather interesting game. X-Men (1993) was based on the popular cartoon version of the comic book series. But it had what was still one of the most unique (and unintuitive)...
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