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>(VL-Bus) ... It wasn’t a massive leap, more like a stopgap improvement on the way to better graphics. >VESA came up with a slightly faster bus standard for th
by rasz 3y ago
>(VL-Bus) ... It wasn’t a massive leap, more like a stopgap improvement on the way to better graphics.
>VESA came up with a slightly faster bus standard for the next generation of graphics cards, one just fast enough to meet the needs of 486 users.
from 5MB/s to 133MB/s not a massive leap, just slightly faster, ok :)
>Intel didn’t exactly make that point clear to the companies supporting the VESA standards body until it was too late for them to react.
Those companies didnt care. Adding VLB to a 486 motherboard cost below 1$ by reusing excess stock of failed standard MCA connectors. Adding PCI meant big expensive PCI bridge chip or developing next generation chipset and impedance matched PCB to satisfy PCI reflected wave switching requirements. VLB was a quick hack to give users what was needed at the time at the price they were willing to pay. Market wasnt ready to pay for PCI in 1992, two years later cost came down to earth.
- yuhong 3y ago[dead]
- hyperman1 3y ago5mb/s is on the low side. Isa ran on the same clock as the cpu. We started there, but things got better quickly. I think the hard limit was a bit below 40MHz, as people still used 74HC chips for glue logic. Combined with EISA 16 bits = 2 bytes per cycle this might give you a 80MB/s theoretical EISA peak. I had an EISA based 386 running 40MHz at the time. Interestingly, VESA's 133MHz is double this, so maybe the majority of the speed gain was doubling bus width to 32bit?
- rasz 3y agoWe started at 8 bit 4.77MHz with 4 clocks minimum so 1MB/s. We ended at around 12MHz in some crazy Turbo XT/AT clones, anything faster was back to ~8MHz with fancier BIOSes giving you option to overclock. You are thinking cpu fsb, ISA never ran at 40MHz. Even EISA ran at a fixed ~8MHz. Btw EISA is not those longer black ISA slots on normal boards, EISA is brown slots with too many pins between normal pins because its secretly a 32bit bus, found pretty much only on workstation/server boards from 1989-1994.
- hyperman1 3y agoYou made me curious, so I looked it up: https://en.wikipedia.org/wiki/List_of_interface_bit_rates https://en.wikipedia.org/wiki/List_of_interface_bit_rates It lists: The original case: ISA 8-Bit/4.77 MHz - 0 W/S: every 4 clocks 1 byte , so basically what you say. The best case; EISA 32-bit/8.33 MHz : 33.32 MB/s So a lot worse than VESA, but still better than 5Mb/s
- hulitu 3y agoWasn't VESA and VLB the same thing ? VLB stands AFAIK for VESA Local Bus.