I replaced the ST with a Pentium laptop running Linux and was briefly exposed to Windows 3.1 and 3.11 and DOS at work where I was the Unix admin (SCO Unix). I then had a 3b2/400 with old AT&T Unix Sys III. College had just purchased shiny new 486 machines for the computer lab.
#Olivetti photo plus software#
I then learned 80×86 assembler running it on a painfully slow software emulator on the ST. That grew into an Atari ST, and 68000 machine with 4MB, learning C and 68K machine code, as well as learning Unix.
And, yes I was a kid) where I started delving into graphics, sound, and eventually DLI programming and assembler. I think it was an 8080? My next machine was the Atari 800 (6502? 48K RAM. I started on the TRS-80 Model 1 back in ’76 or ’77 where I learned BASIC. This was going to be the next post on the subject. The interesting thing is that it’s possible to use the same kind of thinking to design a usable Virtual Memory system for a real 80286, by making sure that segments are allocated in mutliples of 4kB blocks (allowing small far pointer memory allocations being allocated to existing 4kB blocks where possible). 8068 compatibility could then be managed by having the segment registers map to 16 byte paragraphs as before. A while back I wrote blog post about how an alternative 80286 with segment registers pointing to 256 byte paragraphs giving a true 24-bit virtual address which was then paged into a 24-bit physical address space. The designers of the 80286 based it on the Multics segmentation model, but in reality segmentation makes it really hard to implement, because of internal memory fragmentation. Yes! Glad someone comments to say the 80286 did support Virtual Memory (with 1GB per process). Posted in Retrocomputing Tagged 286, 80286, intel, undocumented instructions Post navigation They appear from time to time here, even being connected to the internet.Ģ86 image: Thomas Nguyen (), CC BY-SA 4.0.
#Olivetti photo plus code#
The 286s time as the new hotness was soon blasted away by the 386 with its support for virtual memory, so for most of us it remains as simply a faster way that we ran 8086 code for a few years. The 286 was famous for its fancy extended mode taking rather a long time to switch to, and these instructions relate to loading and saving states before and after the switch. It’s in these fields that the undocumented instructions sit, and they relate to an in-circuit emulator, a 286 with a debug port on some of its unused pins, which would have sat on a plug-in daughterboard for systems under test. During manufacture and testing though, the processor had need of some extra functions, both for testing the chip itself and for debugging designs using it. If you used a 286 it was probably as an end-user sitting in front of a PC-AT or clone. Along the way we learn a bit about the 286, and about why Intel had some of these undocumented instructions in the first place.
As with many microprocessors, it has a few undocumented features, and it’s a couple of these that takes a look at. It brought a new mode that could address up to 16 Mb of memory, and a welcome speed boost over machines using an 8086 or 8088. Should you receive such product and find it unsatisfactory, you may return the product for an exchange or refund.Though it is largely forgotten today, the Intel 80286 was for a while in the 1980s the processor of choice and designated successor to the 8086 in the world of PCs. Our Customer Care team will contact you in such cases, to make sure you are informed about the substitution. At such times, reserves the right to use different brands of product as long as they are equal in price, performance and quality to expedite the shipment of your order.
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