Recent content by exdeath

How exactly are device drivers and interrupt handlers connected?

Device occupies memory addresses and IO ports. It has a protocol for sending it commands, checking status, etc at those addresses. It supports hardware interrupts to achieve concurrency by allowing the CPU to move on and not babysit (eg polling in a loop). Host OS knows nothing about the...
- exdeath
- Post #4
- May 30, 2017
- Forum: Programming
Does anyone have a comprehensive explanation of how the graphics system works?

Call BIOS / VIDEO INT 10 to set mode 13h. Write bytes to A000:0000-FFFF in 256 color index mode and they appear on the screen. Address = y * 320 + x. Change palettes by setting pallette index to IO 3C8 and 3 successive writes to 3C9 with your RGB triplet. Simple as that. Should be some old...
- exdeath
- Post #3
- May 27, 2017
- Forum: Programming
Three teenage burglars shot dead in Oklahoma. An AR-15 was used

The projectile might go clean through, but the 12 inches of tissue around the bullet track will be turned into syrup and nearly every peripheral blood vessel from your toes and fingers to eyes and brain will over pressurize and rupture causing multiple organ failure. Center fire rifle...
- exdeath
- Post #269
- Apr 9, 2017
- Forum: Politics and News
Is IT work a dead-end?

Depends what you call IT. Plugging prefab parts into consumer PCs and turning them on or answering the phone is not IT. Too many people get away with putting words like "Cisco" or "VMware" on their resume and all they know for troubleshooting is what they learned in a class or "ping everything...
- exdeath
- Post #52
- Mar 17, 2017
- Forum: OT Discussion Club
Should one start learning programming from assembly?

And these opinions are why today's fresh Java generation programmers know nothing about microprocessor and machine architecture and why it takes 8 GB RAM to play Tic Tac Toe in a web browser. Understanding assembly, even if not to program with it, but to understand fundamentals that haven't...
- exdeath
- Post #11
- Mar 16, 2017
- Forum: Programming
How big is the processor's execution window for code optimization?

The scope only goes so far as there are available execution units, rename registers, reservation stations, and pipeline stages. The entire point is simply to keep all resources doing something every clock. It's not about optimizing code, it's about the decode and schedule unit avoiding stalls...
- exdeath
- Post #6
- Mar 9, 2017
- Forum: Programming
Data transfer between data segments

You testing any of this yourself yet? You are getting in way too deep for someone who isn't even writing code and observing. An assembler would have told you instantly that mov mem, mem is invalid and you'd see it isn't in the opcode matrix.
- exdeath
- Post #4
- Feb 5, 2017
- Forum: Programming
Data transfer between data segments

mov mem, mem isn't valid at all period. It's a CPU not a DMAC. Mov with mem as an operand is either a load or store not both, thus only one operand can be mem not both. Excepting special complex CISC opcodes like rep and movs_ that take many many cycles and perform many separate operations and...
- exdeath
- Post #3
- Feb 5, 2017
- Forum: Programming
Intel syntax assembly code using dereferenced pointers as offsets

[ ] specifies a memory access. Without brackets you just do a register to register move. This type of syntax is merely to specify intended addressing mode so the assembler spits out the correct opcode. If you specify an explicit segment prefix or segment override it's obvious you want a memory...
- exdeath
- Post #2
- Jan 28, 2017
- Forum: Programming
Calling a procedure that exists in another code segment

I haven't looked at 64 bit implementations of Windows in depth.
- exdeath
- Post #17
- Jan 23, 2017
- Forum: Programming
Python or powershell for automation?

Sounds like this is primarily Windows and MS products you are working with so PowerShell is the way to go.
- exdeath
- Post #5
- Jan 22, 2017
- Forum: Programming
Start with SQL or ACCESS?

You can use Access with ODBC connectivity to use simple SQL queries but if you are serious I'd get a real RDBMS. MySQL, Postgres, SQL server , Oracle, etc. There are numerous advanced topics you won't be able to perform with Access. I don't know what all Access supports now days but I don't...
- exdeath
- Post #2
- Jan 22, 2017
- Forum: Programming
Calling a procedure that exists in another code segment

Extra credit: When you get into virtualization extensions for hardware virtualization to run hypervisors like ESXi, you basically have a privilege level -1 below 0 that lets you both multi task ring 0 processes and more importantly isolate them from knowing about each other.
- exdeath
- Post #15
- Jan 21, 2017
- Forum: Programming
Calling a procedure that exists in another code segment

Given that the portion of hardware we are taking about is the operating system's responsibility to program, and was put into the processor to facilitate OS protection, process isolation, and multitasking, you have to understand both at the same time. The answer is paging. Segmentation is no...
- exdeath
- Post #14
- Jan 21, 2017
- Forum: Programming
Calling a procedure that exists in another code segment

Saw this today on wiki, good recap on why you need a minimum of 2 segments per privilege level and why a typical OS with 2 privilege levels needs 4 identical segments to disable segmentation. In protected mode a segment can not be both writable and executable.[2][3] Therefore, when implementing...
- exdeath
- Post #12
- Jan 15, 2017
- Forum: Programming

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