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How did the early Macintoshes update the display?
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This question is about the Macintosh 128k, but if you can give an answer which describes one of the other very similar machines, that's good too.
The bitmap was 512 by 384 pixels. Assuming that one byte stores eight pixels, so that the CPU can read or update 16 bits in a single bus cycle, that means it would take 10 944 bus cycles to re-write the entire display. Assuming it used something like a move.w a0+, a1+ which is 12 cycles, I calculate that to take around 0.3 seconds to copy a bitmap onto the screen, at 8 MHz. Add to that a variable number of roxl or roxr instructions (in case you want to scroll or move something some pixels to the left or right), and overhead for even a generously unrolled loop, you've got a dog slow GUI.
Another problem is that we have a mouse, but apparently no sprite hardware. So now we need to copy around a (partial) shadow of the bitmap, overlaying the cursor with and and or, whenever the user moves the mouse.
This link does not list any hardware which was obviously intended to alleviate these problems.
So how did this line of "classic macs" address the problem of scrolling and moving large areas, or rendering a mouse cursor?
graphics apple-macintosh
asked 2 hours ago
Wilson
9,217541112
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up vote
2
down vote
favorite
This question is about the Macintosh 128k, but if you can give an answer which describes one of the other very similar machines, that's good too.
The bitmap was 512 by 384 pixels. Assuming that one byte stores eight pixels, so that the CPU can read or update 16 bits in a single bus cycle, that means it would take 10 944 bus cycles to re-write the entire display. Assuming it used something like a move.w a0+, a1+ which is 12 cycles, I calculate that to take around 0.3 seconds to copy a bitmap onto the screen, at 8 MHz. Add to that a variable number of roxl or roxr instructions (in case you want to scroll or move something some pixels to the left or right), and overhead for even a generously unrolled loop, you've got a dog slow GUI.
Another problem is that we have a mouse, but apparently no sprite hardware. So now we need to copy around a (partial) shadow of the bitmap, overlaying the cursor with and and or, whenever the user moves the mouse.
This link does not list any hardware which was obviously intended to alleviate these problems.
So how did this line of "classic macs" address the problem of scrolling and moving large areas, or rendering a mouse cursor?
graphics apple-macintosh
asked 2 hours ago
Wilson
9,217541112
add a comment |Â
up vote
2
down vote
favorite
up vote
2
down vote
favorite
This question is about the Macintosh 128k, but if you can give an answer which describes one of the other very similar machines, that's good too.
The bitmap was 512 by 384 pixels. Assuming that one byte stores eight pixels, so that the CPU can read or update 16 bits in a single bus cycle, that means it would take 10 944 bus cycles to re-write the entire display. Assuming it used something like a move.w a0+, a1+ which is 12 cycles, I calculate that to take around 0.3 seconds to copy a bitmap onto the screen, at 8 MHz. Add to that a variable number of roxl or roxr instructions (in case you want to scroll or move something some pixels to the left or right), and overhead for even a generously unrolled loop, you've got a dog slow GUI.
Another problem is that we have a mouse, but apparently no sprite hardware. So now we need to copy around a (partial) shadow of the bitmap, overlaying the cursor with and and or, whenever the user moves the mouse.
This link does not list any hardware which was obviously intended to alleviate these problems.
So how did this line of "classic macs" address the problem of scrolling and moving large areas, or rendering a mouse cursor?
graphics apple-macintosh
asked 2 hours ago
Wilson
9,217541112
This question is about the Macintosh 128k, but if you can give an answer which describes one of the other very similar machines, that's good too.
The bitmap was 512 by 384 pixels. Assuming that one byte stores eight pixels, so that the CPU can read or update 16 bits in a single bus cycle, that means it would take 10 944 bus cycles to re-write the entire display. Assuming it used something like a move.w a0+, a1+ which is 12 cycles, I calculate that to take around 0.3 seconds to copy a bitmap onto the screen, at 8 MHz. Add to that a variable number of roxl or roxr instructions (in case you want to scroll or move something some pixels to the left or right), and overhead for even a generously unrolled loop, you've got a dog slow GUI.
Another problem is that we have a mouse, but apparently no sprite hardware. So now we need to copy around a (partial) shadow of the bitmap, overlaying the cursor with and and or, whenever the user moves the mouse.
This link does not list any hardware which was obviously intended to alleviate these problems.
So how did this line of "classic macs" address the problem of scrolling and moving large areas, or rendering a mouse cursor?
graphics apple-macintosh
graphics apple-macintosh
asked 2 hours ago
Wilson
9,217541112
asked 2 hours ago
Wilson
9,217541112
asked 2 hours ago
Wilson
9,217541112
asked 2 hours ago
Wilson
9,217541112
asked 2 hours ago
Wilson
9,217541112
9,217541112
add a comment |Â
add a comment |Â
2 Answers
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TL;DR: Exactly as you assume. The CPU shovelled the data around, even way slower than your calculation suggests, and everyone was happy about the high speed with which it happened :)
To be honest, I'm not complete sure what your question is. It was a plain bitmap display (like you assumed) and quite sufficient to be handled by the CPU. After all, no-one was thinking of real time video back then. Just a UI and whatever the running application wants to display. And for this a CPU is quite sufficient.
Moving a mouse cursor needs at maximum the manipulation of twice 16 bytes (in case of an 8x8). One for undrawing the existing one, one for drawing it at a new position. That's few enough when done every frame for a fast moving one. In reality the mouse doesn't move at all most of the time, so no redraw is needed.
Similar, the display doesn't get changed a lot. Sure, every time a key gets pressed a character is to be drawn. Not a big deal. Several can be done between frames.
Worst case here would be scrolling up at the end of a line, or inserting a character in the topmost line of a window. This may take time to (re)draw the entire window, but then again, it's a rare case and even if it lags by like .2 seconds, it's way acceptable.
Yes, the Mac was slow in drawing a whole screen, but it wasn't exceptionally slow, or slower than other machines of that time. Especially not considering the nice look it had :))
Just compare it to similar machines of about the same time frame. Inserting a character at a top line and wrapping the rest down equals a redraw of the whole text screen. On a 9,600 bps terminal that equals to more than two whole seconds. An Apple II with its built-in 40x24 screen needed about 0.04 seconds (already more than 2 frames) to do the same (*1) and with an 80 column card it may have taken as much as .1 seconds. So while one could notice a little lag when scrolling on a Mac, it was way within its competition.
Today we are used to instantly updated of humungous high resolution screens, no matter what happens. Back then no-one watched videos on a PC. Heck, simple animations of a few pixels were already considered awesome.
Bottom line, there was no such problem.
*1 - That's hand written assembly optimized for that case.
answered 2 hours ago
Raffzahn
38.8k487156
+1. It’s easy to forget how few screen updates there were in old GUIs; scrolling didn’t update contents in real time, nor did moving windows etc.
– Stephen Kitt
19 mins ago
add a comment |Â
up vote
0
down vote
As others have said, refreshing the whole screen in a fraction of a second was considered blindingly fast at that time.
The Mac's biggest early advantage, though, was the QuickDraw framework. This was leaps and bounds ahead of other graphics packages of the day, both in functionality and efficiency. With QuickDraw, you rarely had to rewrite the whole display -- instead, you'd work within a GrafPort representing a window's content pane, and manipulate Regions that touched only affected pixels, not an entire rectangular bounding box.
At the time the Mac was introduced, a 16-bit 8-MHz 68000 was actually respectably fast in comparison to its competition. But it felt AMAZINGLY fast.
answered 4 mins ago
jeffB
38616
add a comment |Â
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
3
down vote
TL;DR: Exactly as you assume. The CPU shovelled the data around, even way slower than your calculation suggests, and everyone was happy about the high speed with which it happened :)
To be honest, I'm not complete sure what your question is. It was a plain bitmap display (like you assumed) and quite sufficient to be handled by the CPU. After all, no-one was thinking of real time video back then. Just a UI and whatever the running application wants to display. And for this a CPU is quite sufficient.
Moving a mouse cursor needs at maximum the manipulation of twice 16 bytes (in case of an 8x8). One for undrawing the existing one, one for drawing it at a new position. That's few enough when done every frame for a fast moving one. In reality the mouse doesn't move at all most of the time, so no redraw is needed.
Similar, the display doesn't get changed a lot. Sure, every time a key gets pressed a character is to be drawn. Not a big deal. Several can be done between frames.
Worst case here would be scrolling up at the end of a line, or inserting a character in the topmost line of a window. This may take time to (re)draw the entire window, but then again, it's a rare case and even if it lags by like .2 seconds, it's way acceptable.
Yes, the Mac was slow in drawing a whole screen, but it wasn't exceptionally slow, or slower than other machines of that time. Especially not considering the nice look it had :))
Just compare it to similar machines of about the same time frame. Inserting a character at a top line and wrapping the rest down equals a redraw of the whole text screen. On a 9,600 bps terminal that equals to more than two whole seconds. An Apple II with its built-in 40x24 screen needed about 0.04 seconds (already more than 2 frames) to do the same (*1) and with an 80 column card it may have taken as much as .1 seconds. So while one could notice a little lag when scrolling on a Mac, it was way within its competition.
Today we are used to instantly updated of humungous high resolution screens, no matter what happens. Back then no-one watched videos on a PC. Heck, simple animations of a few pixels were already considered awesome.
Bottom line, there was no such problem.
*1 - That's hand written assembly optimized for that case.
answered 2 hours ago
Raffzahn
38.8k487156
+1. It’s easy to forget how few screen updates there were in old GUIs; scrolling didn’t update contents in real time, nor did moving windows etc.
– Stephen Kitt
19 mins ago
add a comment |Â
up vote
3
down vote
TL;DR: Exactly as you assume. The CPU shovelled the data around, even way slower than your calculation suggests, and everyone was happy about the high speed with which it happened :)
To be honest, I'm not complete sure what your question is. It was a plain bitmap display (like you assumed) and quite sufficient to be handled by the CPU. After all, no-one was thinking of real time video back then. Just a UI and whatever the running application wants to display. And for this a CPU is quite sufficient.
Moving a mouse cursor needs at maximum the manipulation of twice 16 bytes (in case of an 8x8). One for undrawing the existing one, one for drawing it at a new position. That's few enough when done every frame for a fast moving one. In reality the mouse doesn't move at all most of the time, so no redraw is needed.
Similar, the display doesn't get changed a lot. Sure, every time a key gets pressed a character is to be drawn. Not a big deal. Several can be done between frames.
Worst case here would be scrolling up at the end of a line, or inserting a character in the topmost line of a window. This may take time to (re)draw the entire window, but then again, it's a rare case and even if it lags by like .2 seconds, it's way acceptable.
Yes, the Mac was slow in drawing a whole screen, but it wasn't exceptionally slow, or slower than other machines of that time. Especially not considering the nice look it had :))
Just compare it to similar machines of about the same time frame. Inserting a character at a top line and wrapping the rest down equals a redraw of the whole text screen. On a 9,600 bps terminal that equals to more than two whole seconds. An Apple II with its built-in 40x24 screen needed about 0.04 seconds (already more than 2 frames) to do the same (*1) and with an 80 column card it may have taken as much as .1 seconds. So while one could notice a little lag when scrolling on a Mac, it was way within its competition.
Today we are used to instantly updated of humungous high resolution screens, no matter what happens. Back then no-one watched videos on a PC. Heck, simple animations of a few pixels were already considered awesome.
Bottom line, there was no such problem.
*1 - That's hand written assembly optimized for that case.
answered 2 hours ago
Raffzahn
38.8k487156
+1. It’s easy to forget how few screen updates there were in old GUIs; scrolling didn’t update contents in real time, nor did moving windows etc.
– Stephen Kitt
19 mins ago
add a comment |Â
up vote
3
down vote
up vote
3
down vote
TL;DR: Exactly as you assume. The CPU shovelled the data around, even way slower than your calculation suggests, and everyone was happy about the high speed with which it happened :)
To be honest, I'm not complete sure what your question is. It was a plain bitmap display (like you assumed) and quite sufficient to be handled by the CPU. After all, no-one was thinking of real time video back then. Just a UI and whatever the running application wants to display. And for this a CPU is quite sufficient.
Moving a mouse cursor needs at maximum the manipulation of twice 16 bytes (in case of an 8x8). One for undrawing the existing one, one for drawing it at a new position. That's few enough when done every frame for a fast moving one. In reality the mouse doesn't move at all most of the time, so no redraw is needed.
Similar, the display doesn't get changed a lot. Sure, every time a key gets pressed a character is to be drawn. Not a big deal. Several can be done between frames.
Worst case here would be scrolling up at the end of a line, or inserting a character in the topmost line of a window. This may take time to (re)draw the entire window, but then again, it's a rare case and even if it lags by like .2 seconds, it's way acceptable.
Yes, the Mac was slow in drawing a whole screen, but it wasn't exceptionally slow, or slower than other machines of that time. Especially not considering the nice look it had :))
Just compare it to similar machines of about the same time frame. Inserting a character at a top line and wrapping the rest down equals a redraw of the whole text screen. On a 9,600 bps terminal that equals to more than two whole seconds. An Apple II with its built-in 40x24 screen needed about 0.04 seconds (already more than 2 frames) to do the same (*1) and with an 80 column card it may have taken as much as .1 seconds. So while one could notice a little lag when scrolling on a Mac, it was way within its competition.
Today we are used to instantly updated of humungous high resolution screens, no matter what happens. Back then no-one watched videos on a PC. Heck, simple animations of a few pixels were already considered awesome.
Bottom line, there was no such problem.
*1 - That's hand written assembly optimized for that case.
answered 2 hours ago
Raffzahn
38.8k487156
TL;DR: Exactly as you assume. The CPU shovelled the data around, even way slower than your calculation suggests, and everyone was happy about the high speed with which it happened :)
To be honest, I'm not complete sure what your question is. It was a plain bitmap display (like you assumed) and quite sufficient to be handled by the CPU. After all, no-one was thinking of real time video back then. Just a UI and whatever the running application wants to display. And for this a CPU is quite sufficient.
Moving a mouse cursor needs at maximum the manipulation of twice 16 bytes (in case of an 8x8). One for undrawing the existing one, one for drawing it at a new position. That's few enough when done every frame for a fast moving one. In reality the mouse doesn't move at all most of the time, so no redraw is needed.
Similar, the display doesn't get changed a lot. Sure, every time a key gets pressed a character is to be drawn. Not a big deal. Several can be done between frames.
Worst case here would be scrolling up at the end of a line, or inserting a character in the topmost line of a window. This may take time to (re)draw the entire window, but then again, it's a rare case and even if it lags by like .2 seconds, it's way acceptable.
Yes, the Mac was slow in drawing a whole screen, but it wasn't exceptionally slow, or slower than other machines of that time. Especially not considering the nice look it had :))
Just compare it to similar machines of about the same time frame. Inserting a character at a top line and wrapping the rest down equals a redraw of the whole text screen. On a 9,600 bps terminal that equals to more than two whole seconds. An Apple II with its built-in 40x24 screen needed about 0.04 seconds (already more than 2 frames) to do the same (*1) and with an 80 column card it may have taken as much as .1 seconds. So while one could notice a little lag when scrolling on a Mac, it was way within its competition.
Today we are used to instantly updated of humungous high resolution screens, no matter what happens. Back then no-one watched videos on a PC. Heck, simple animations of a few pixels were already considered awesome.
Bottom line, there was no such problem.
*1 - That's hand written assembly optimized for that case.
answered 2 hours ago
Raffzahn
38.8k487156
edited 1 hour ago
answered 2 hours ago
Raffzahn
38.8k487156
answered 2 hours ago
Raffzahn
38.8k487156
answered 2 hours ago
Raffzahn
38.8k487156
38.8k487156
+1. It’s easy to forget how few screen updates there were in old GUIs; scrolling didn’t update contents in real time, nor did moving windows etc.
– Stephen Kitt
19 mins ago
add a comment |Â
+1. It’s easy to forget how few screen updates there were in old GUIs; scrolling didn’t update contents in real time, nor did moving windows etc.
– Stephen Kitt
19 mins ago
+1. It’s easy to forget how few screen updates there were in old GUIs; scrolling didn’t update contents in real time, nor did moving windows etc.
– Stephen Kitt
19 mins ago
+1. It’s easy to forget how few screen updates there were in old GUIs; scrolling didn’t update contents in real time, nor did moving windows etc.
– Stephen Kitt
19 mins ago
add a comment |Â
up vote
0
down vote
As others have said, refreshing the whole screen in a fraction of a second was considered blindingly fast at that time.
The Mac's biggest early advantage, though, was the QuickDraw framework. This was leaps and bounds ahead of other graphics packages of the day, both in functionality and efficiency. With QuickDraw, you rarely had to rewrite the whole display -- instead, you'd work within a GrafPort representing a window's content pane, and manipulate Regions that touched only affected pixels, not an entire rectangular bounding box.
At the time the Mac was introduced, a 16-bit 8-MHz 68000 was actually respectably fast in comparison to its competition. But it felt AMAZINGLY fast.
answered 4 mins ago
jeffB
38616
add a comment |Â
up vote
0
down vote
As others have said, refreshing the whole screen in a fraction of a second was considered blindingly fast at that time.
The Mac's biggest early advantage, though, was the QuickDraw framework. This was leaps and bounds ahead of other graphics packages of the day, both in functionality and efficiency. With QuickDraw, you rarely had to rewrite the whole display -- instead, you'd work within a GrafPort representing a window's content pane, and manipulate Regions that touched only affected pixels, not an entire rectangular bounding box.
At the time the Mac was introduced, a 16-bit 8-MHz 68000 was actually respectably fast in comparison to its competition. But it felt AMAZINGLY fast.
answered 4 mins ago
jeffB
38616
add a comment |Â
up vote
0
down vote
up vote
0
down vote
As others have said, refreshing the whole screen in a fraction of a second was considered blindingly fast at that time.
The Mac's biggest early advantage, though, was the QuickDraw framework. This was leaps and bounds ahead of other graphics packages of the day, both in functionality and efficiency. With QuickDraw, you rarely had to rewrite the whole display -- instead, you'd work within a GrafPort representing a window's content pane, and manipulate Regions that touched only affected pixels, not an entire rectangular bounding box.
At the time the Mac was introduced, a 16-bit 8-MHz 68000 was actually respectably fast in comparison to its competition. But it felt AMAZINGLY fast.
answered 4 mins ago
jeffB
38616
As others have said, refreshing the whole screen in a fraction of a second was considered blindingly fast at that time.
The Mac's biggest early advantage, though, was the QuickDraw framework. This was leaps and bounds ahead of other graphics packages of the day, both in functionality and efficiency. With QuickDraw, you rarely had to rewrite the whole display -- instead, you'd work within a GrafPort representing a window's content pane, and manipulate Regions that touched only affected pixels, not an entire rectangular bounding box.
At the time the Mac was introduced, a 16-bit 8-MHz 68000 was actually respectably fast in comparison to its competition. But it felt AMAZINGLY fast.
answered 4 mins ago
jeffB
38616
answered 4 mins ago
jeffB
38616
answered 4 mins ago
jeffB
38616
answered 4 mins ago
jeffB
38616
38616
add a comment |Â
add a comment |Â
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