Parto con due osservazioni:
- il Jaguar monta un 68000 a 16 mhz, identico a quello del Panther
- sulla console esistono giochi molto lenti ed altri che sembrano "a 16 bit"
Questo perché usano solo il 68000?
Raiden e Crescent Galaxy sono giochi che erano pronti per il Panther e mai pubblicati, che siano stati portati su Jaguar basandosi solo sul 68000 sembrerebbe verosimile, così come per similitudine hardware altri giochi presi pari pari da Amiga, ma sono supposizioni alle quali non posso far seguire conferme.
Ho trovato, invece, discussioni molto interessanti (in inglese) sul ruolo del 68000 e di come avesse ruolo molto attivo nel quadro completo di alcune indecenti prestazioni della macchina.
Domanda ad uno sviluppatore hardware del Jaguar:
The Jaguar used a 68000. Isn't that the CPU?
Again, quoting from Jaguar designer John Mathieson, "It may be the CPU in
the sense that it's the centre of operation, and boot-straps the machine,
and starts everything else going; however, it is not the centre of
Jaguar's power. ... The 68000 is like a manager who does no real work, but
tells everybody else what to do."
Quindi il 68000 non dovrebbe incidere negativamente, ma vediamo cosa dicono altri.
Qui siamo su un forum dedicato al Jaguar:
The Jag only has three traditionally programmable processors - the 68k and two 32-bit RISC chips. The Object Processor can only be used to generate the display (it can't output data anywhere but the line buffers and has rather limited decision making), and the blitter just moves and formats data, it's not a programmable or scriptable processor on its own. Only the Object Processor and the Blitter deal with 64-bits at a time, although the GPU has a single instruction to load and a second to store a 64-bit value (but it must treat it as two 32-bit values for all other operations and can only manage one at a time).
Since you can halt the 68k, and doing so causes no impact to the rest of the system, having it there to boot the machine doesn't hamper anything at all. However, it did appear to cause a perceptual issue -- since it could talk to every other part of the machine, and because it has the fewest limitations in the system, not to mention how familiar it was, developers fell to it. It was already faster than the 68k in any of the game systems of the day, and even most home computers.
Quindi, secondo questo utente, al 68000 gli sviluppatori affidano più di quanto avrebbero dovuto dato che non aveva limiti, era molto noto ed era cmq più veloci dei suoi simili sulle altre console. Leggiamo le sue conclusioni:
The biggest reason the 68k causes problems in the Jaguar is not the 68k's performance, nor is it a loss of potential, really, it's because the 68k sucks bandwidth from the rest of the processors. The Jaguar has a single unified bus for everything -- video, GPU, DSP, blitter, object processor, RAM, line buffers, 68k -- there's only one bus. When any chip needs it, no other chip can use it. The problem here is two-fold:
First, the 68k is only 16-bits wide, but works with 32-bit words. So every time it seizes the bus, it needs at least two cycles. (Generally speaking).
Second, the 68k is the slowest clocked processor in the machine, running at half the clock rate of the RISCs. So even though the DSP is also wired at 16-bits and works 32-bits at a time, it can get those 32-bits in half the time. (The DSP is also a little more advanced in how it can treat memory, and has internal cache to reduce the need to do this anyway).
Insomma, i programmatori svogliati che si ostinavano a passare dal 68000 rimanevano bloccati in un tremendo collo di bottiglia. Quest'altro utente ribadisce la cosa con vigore:
the M68k is NOT the Jaguar CPU!
The Jaguar does not have a CPU, its a custom chip set and was designed to use all at once with each doing its own job, hence no CPU is actually needed.
Those games you mentioned all use the M68k to execute the games which is why they have slowdown, this occurs when the bus is being choked or low fram rates because it can't update quick enough. Remember that the graphics are still being drawn by a 64-bit chip but being send to the M68k for execution.
Go look at Iron Soldier 2, Hoverstrike CD, Missile Command 3D or Zero 5 and you will see some wonderful 3D graphics comparable to anything from the early Saturn/PS1 days. Simply because these games were programmed how it was intended they should be using all the custom chips at once.
Per concludere, secondo questi ragazzi e il progettista di sopra, il 68000 doveva servire per bootstrap e le altre operazioni di cui parlava Dr_Who nell'altro thread, ma molti programmatori "pigri" abusavano di questo processore per facilità di sviluppo, combinandone di tutti i colori.
- il Jaguar monta un 68000 a 16 mhz, identico a quello del Panther
- sulla console esistono giochi molto lenti ed altri che sembrano "a 16 bit"
Questo perché usano solo il 68000?
Raiden e Crescent Galaxy sono giochi che erano pronti per il Panther e mai pubblicati, che siano stati portati su Jaguar basandosi solo sul 68000 sembrerebbe verosimile, così come per similitudine hardware altri giochi presi pari pari da Amiga, ma sono supposizioni alle quali non posso far seguire conferme.
Ho trovato, invece, discussioni molto interessanti (in inglese) sul ruolo del 68000 e di come avesse ruolo molto attivo nel quadro completo di alcune indecenti prestazioni della macchina.
Domanda ad uno sviluppatore hardware del Jaguar:
The Jaguar used a 68000. Isn't that the CPU?
Again, quoting from Jaguar designer John Mathieson, "It may be the CPU in
the sense that it's the centre of operation, and boot-straps the machine,
and starts everything else going; however, it is not the centre of
Jaguar's power. ... The 68000 is like a manager who does no real work, but
tells everybody else what to do."
Quindi il 68000 non dovrebbe incidere negativamente, ma vediamo cosa dicono altri.
Qui siamo su un forum dedicato al Jaguar:
The Jag only has three traditionally programmable processors - the 68k and two 32-bit RISC chips. The Object Processor can only be used to generate the display (it can't output data anywhere but the line buffers and has rather limited decision making), and the blitter just moves and formats data, it's not a programmable or scriptable processor on its own. Only the Object Processor and the Blitter deal with 64-bits at a time, although the GPU has a single instruction to load and a second to store a 64-bit value (but it must treat it as two 32-bit values for all other operations and can only manage one at a time).
Since you can halt the 68k, and doing so causes no impact to the rest of the system, having it there to boot the machine doesn't hamper anything at all. However, it did appear to cause a perceptual issue -- since it could talk to every other part of the machine, and because it has the fewest limitations in the system, not to mention how familiar it was, developers fell to it. It was already faster than the 68k in any of the game systems of the day, and even most home computers.
Quindi, secondo questo utente, al 68000 gli sviluppatori affidano più di quanto avrebbero dovuto dato che non aveva limiti, era molto noto ed era cmq più veloci dei suoi simili sulle altre console. Leggiamo le sue conclusioni:
The biggest reason the 68k causes problems in the Jaguar is not the 68k's performance, nor is it a loss of potential, really, it's because the 68k sucks bandwidth from the rest of the processors. The Jaguar has a single unified bus for everything -- video, GPU, DSP, blitter, object processor, RAM, line buffers, 68k -- there's only one bus. When any chip needs it, no other chip can use it. The problem here is two-fold:
First, the 68k is only 16-bits wide, but works with 32-bit words. So every time it seizes the bus, it needs at least two cycles. (Generally speaking).
Second, the 68k is the slowest clocked processor in the machine, running at half the clock rate of the RISCs. So even though the DSP is also wired at 16-bits and works 32-bits at a time, it can get those 32-bits in half the time. (The DSP is also a little more advanced in how it can treat memory, and has internal cache to reduce the need to do this anyway).
Insomma, i programmatori svogliati che si ostinavano a passare dal 68000 rimanevano bloccati in un tremendo collo di bottiglia. Quest'altro utente ribadisce la cosa con vigore:
the M68k is NOT the Jaguar CPU!
The Jaguar does not have a CPU, its a custom chip set and was designed to use all at once with each doing its own job, hence no CPU is actually needed.
Those games you mentioned all use the M68k to execute the games which is why they have slowdown, this occurs when the bus is being choked or low fram rates because it can't update quick enough. Remember that the graphics are still being drawn by a 64-bit chip but being send to the M68k for execution.
Go look at Iron Soldier 2, Hoverstrike CD, Missile Command 3D or Zero 5 and you will see some wonderful 3D graphics comparable to anything from the early Saturn/PS1 days. Simply because these games were programmed how it was intended they should be using all the custom chips at once.
Per concludere, secondo questi ragazzi e il progettista di sopra, il 68000 doveva servire per bootstrap e le altre operazioni di cui parlava Dr_Who nell'altro thread, ma molti programmatori "pigri" abusavano di questo processore per facilità di sviluppo, combinandone di tutti i colori.
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