Grzyb wrote on 2021-04-20, 03:11:It doesn't make sense.
EISA is 32-bit
A1500/A2000 is 16-bit […]
Show full quote
Jo22 wrote on 2021-04-19, 11:00:
A replacement, aftermarket EISA backplane for the A1500/A2000 would have had been a wise decision here.
It doesn't make sense.
EISA is 32-bit
A1500/A2000 is 16-bit
Chances are, that Zorro<->ISA bridge wasn't a bottleneck, at least in an A2000.
ISA is 16-bit 8MHz - slow, but still seems faster than the 68000@7MHz bus.
I was thinking of bridge boards and accellerator boards..
EISA could have been a robust alternative to PCI that didn't break ISA compatibility.
Because, EISA was a serious server technology. The ET4000 existed in EISA* variants, too.
32-Bit or not, it might have been less stressing to use EISA slots instead, because that bus had more head room than pure ISA.
Ie, multiple cards on the EISA side could have had talked to each other at quick speeds without slowing the whole bus down.
I'm tinking of netword cards, IDE controllers, SVGA cards. On ISA, each of them alone has the ability to demand capacity of the whole bus.
That's why even on low-end PC platforms, ISA was a bottle-neck.
And the ET4000 was quick not only because of the VGA core itself, but also its FiFo buffer.
Sure, ISA had a higher clock rate. But who in his/her right mind ran an 68k/7Mhz freely in 1991/1992 in his/her main "PC"** ?
I mean, even the 68010 was a common replacement. Comparable to what the NEC V20/V30 was on the PC platform.
From what I saw, the Amiga people often were hardware hackers and or at least technically inclined.
Things like RAM or Kick EPROMS often got upgraded, anyway, which is not far from installing a CPU replacement. 😀
Grzyb wrote on 2021-04-20, 03:11:
For A3000 and A4000, however, ISA graphics must have been bad.
If I was looking for some SVGA chipset for use in such Amigas, I would consider something with memory-mapped I/O, like CL-GD5429.
There's no I/O address space in 680x0 CPUs, so a chipset with MMIO would noticably simplify the design.
A3000, A4000. Hm. Weren't these rare, niche, high-end Amigas owned by Amiga fans that came out when the platform reached its end? 😉
I thought the majority of users had Amigas based on A500/A2000 technology.
Personally, I've never met a person that had an A3000/4000. 😅
Edit: ET40oo/W32i datasheet says "The Tseng Labs ET4000/W32i video controller is an ISA/EISA/MCA-compatible graphics chip that delivers an 8-/16-/32-bit bus or CPU direc[..]"
Source: http://www.datasheetcatalog.com/datasheets_pd … 4000-W32I.shtml
Edit: ** Never mind. I'm comming to the conclusion that I'm not quite able to understand the common mind set of real Amiga users. 😅
That being said, I think it was an interesting platform, though. And I do truely appreciate it for its demo and tracker scene, too.
"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel
//My video channel//