Post AsnBGjhPUWL3mZ7dTc by foone@digipres.club
(DIR) More posts by foone@digipres.club
(DIR) Post #AslLbbQzkYSj1U2Wps by foone@digipres.club
2025-04-04T23:29:15Z
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I want an NEC V20 (an 8080 clone) on a USB stick. This doesn't exist, so I'm gonna have to make it
(DIR) Post #AslM0RP8B80p9f0mjg by foone@digipres.club
2025-04-04T23:33:50Z
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Probably an NEC V25 actually, since that's more of a system-on-a-chip. I'd need less support hardware
(DIR) Post #AslM69AUtOeCKmt64e by dryak@mstdn.science
2025-04-04T23:34:46Z
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@foone do badically you'll need a Raspberry Pico 2, and make a miniaturized cousin of PigoMEM / PicoGUS to talk to its bus?
(DIR) Post #AslML2ZvfwQAEwswMK by foone@digipres.club
2025-04-04T23:37:33Z
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A fun thing about the 8080 being so old is that it can address an entire megabyte of ram, so it has a built in DRAM controller.But it's 2025. I can buy a megabyte of SRAM for 5$
(DIR) Post #AslNinNLx0d5zetTRQ by huronbikes@cyberplace.social
2025-04-04T23:52:58Z
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@foone I came across https://microcorelabs.wordpress.com/2024/12/31/mclv20_max-a-software-defined-nec-v20-cpu-and-more/ recently, which uses a Teensy to emulate a V20 for an XT system.
(DIR) Post #AslO2wTDqYSTzYFIUi by ScotttSee@mastodon.sdf.org
2025-04-04T23:56:28Z
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@foone I forgot that the V20 had an 8080 mode.
(DIR) Post #AslPAyyuUhkK3CSuhs by foone@digipres.club
2025-04-05T00:07:11Z
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@huronbikes ooh, that sounds intriguing!
(DIR) Post #AslPTeXtaqCj0NSsDo by RueNahcMohr@infosec.exchange
2025-04-05T00:12:22Z
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@foone your having a day.he means 8088.
(DIR) Post #AslPTf4rcGZkectCbo by RueNahcMohr@infosec.exchange
2025-04-05T00:11:56Z
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@foone er 8088.... ?
(DIR) Post #AslPkpgDRwfESaY3Y8 by huronbikes@cyberplace.social
2025-04-05T00:15:16Z
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@foone yeah! Also yet another reason I wish I still had my 5150
(DIR) Post #AsleKX6An5DKDOwoVc by baljemmett@mastodon.online
2025-04-05T02:58:51Z
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@foone I found myself quite enamoured with the DEC T11's dynamic modes when researching it as part of my recent VT240 resuscitation, and now I find myself wanting to build something around it... This is Very Bad.
(DIR) Post #Aslloh6upXBxdKcl3Q by StompyRobot@mastodon.gamedev.place
2025-04-05T04:22:55Z
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@foone why are you not just emulating it on a ARM or RISC-V with a couple of MB RAM? Would probably run faster, if you wanted it to.Probably cheaper, too!
(DIR) Post #AsluqqKWQGRKOT5VM8 by foone@digipres.club
2025-04-05T06:04:09Z
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@StompyRobot cause what I'm trying to do isn't "emulate an 8080", I can do that easily, I'm instead trying to use a real 8080 on a USB stick
(DIR) Post #AslwAqT9iMAaZUEBeK by TomF@mastodon.gamedev.place
2025-04-05T06:18:59Z
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@foone @StompyRobot What is the difference between an 8080 and an 8088, anyway? Wikipedia suggests it's "just microcode", but that doesn't feel right.
(DIR) Post #AsmD0IlRs8qSMWLHwO by manmachine@bitbang.social
2025-04-05T09:27:32Z
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@foone
(DIR) Post #AsmhC4lKkndH2IoqXY by Kmf@freiburg.social
2025-04-05T15:05:46Z
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@foone Oh the memories, remember the V25 has multiple register sets, which you can switch on the fly, which is very handy for task switching. Had developed a RTOS in the 1990 using this for various hardware controllers (like thermal printer, LCD display).
(DIR) Post #AsmjxXUvvwGffzuMQi by StompyRobot@mastodon.gamedev.place
2025-04-05T15:36:49Z
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@foone Matrix voice: "but would you know the difference?"
(DIR) Post #AsnBBp2SDCwitVcdQu by foone@digipres.club
2025-04-05T20:41:53Z
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@gloriouscow that looks like exactly what I need
(DIR) Post #AsnBGjhPUWL3mZ7dTc by foone@digipres.club
2025-04-05T20:42:07Z
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@gloriouscow typo, I meant V25
(DIR) Post #AsnE2sA7WqQ5q2dFs8 by foone@digipres.club
2025-04-05T21:13:52Z
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@gloriouscow I think I'd need to do a modified PCB, so that won't help, but thanks!
(DIR) Post #Asq2hUp4aprPLjGtmK by KeyJ@mastodon.gamedev.place
2025-04-06T18:45:27Z
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@TomF @foone @StompyRobot The 8080 and 8088 are extremely different - the former is an 8-bit processor, the latter is 16-bit, but with an 8-bit data bus. The 8088 is a cut-down version of the 8086 (a proper 16-bit CPU with a 16-bit bus) and shares the same ISA and ~98% of the microcode with its bigger brother.The 8086/8088 register and instruction sets are proper supersets of the 8080's, making them source-compatible.The NEC V20 is notable in that it's binary-compatible with both.
(DIR) Post #Asq2hW2w2mXj90lU1Y by TomF@mastodon.gamedev.place
2025-04-07T04:17:47Z
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@KeyJ @foone @StompyRobot Right. The way to tell an 8088 from an 8086 is to change a NOP to an INC exactly 5 instructions ahead. Because one has a 4-byte prefecth queue and the other has a 6-byte prefetch queue (but right now I forget which way round).
(DIR) Post #Asq2hX1CQikU9uxbxQ by foone@digipres.club
2025-04-07T05:50:55Z
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@TomF @KeyJ @StompyRobot this is the kind of thing that'd be easy for me to check if I had my NEC V20 on USB
(DIR) Post #AsqBfYX2jMTRrTzJ8y by KeyJ@mastodon.gamedev.place
2025-04-07T07:31:26Z
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@foone @TomF @StompyRobot I'm not sure, but from what I remember, the V20's instruction timings (including the prefetch queue) are very different from the 8088.