5 ms·

> At a time when PC memory maxed out at 640 megabytes, Pretty sure the author meant write 640 kilobytes.

rjsw 1y ago
Maybe that is what they were thinking but anything designed to work with a PCI bus would have been introduced after PCs became capable of using more memory than that.
usefulcat 1y ago
It's hard to tell exactly what time frame the author is referencing there. For context, NV1 was released in '95, by which time it was not uncommon for a new PC to have 8-16 MB of memory (I had a 486 with 16 MB by '94). Especially if you planned to use it for gaming.
npalli 1y ago
The sentence and paragraph which makes it clear that this was megabytes and not kilobytes At a time when PC memory maxed out at 640 megabytes, the fact that the PCI bus could address 4 gigabytes meant that quite a few of its address bits were surplus. So we decided to increase the amount of data shipped in each bus cycle by using some of them as data. IIRC NV1 used 23 address bits, occupying 1/512th of the total space. 7 of the 23 selected one of the 128 virtual FIFOs, allowing 128 different processes to share access to the hardware. We figured 128 processes was plenty.
- AStonesThrow 1y ago
  Okay but "640" is a completely fictitious number for installed RAM in any given PC. PC memory was nearly always sold in powers of two. So you could have SIMMs in capacity of 1MiB, 2MiB, 4, 8, 16MiB. You could usually mix-and-match these memory modules, and some PCs had 2 slots, some had 4, some had a different number of slots. So if you think about 4 slots that can hold some sort of maximum, we're thinking 64MiB is a very common maximum for a consumer PC, and that may be 2x32 or 4x16MiB. Lots of people ran up against that limit for sure. 640MiB is an absurd number if you think mathematically. How do you divide that up? If 4 SIMMs are installed, then their capacity is 160MiB each? No such hardware ever existed. IIRC, individual SIMMs were commonly maxed at 64MiB, and it was not physically possible to make a "monster memory module" larger than that. Furthermore, while 64MiB requires 26 bits to address, 640MiB requires 30 address bits on the bus. If a hypothetical PC had 640MiB in use by the OS, then only 2 pins would be unused on the address bus! That is clearly at odds with their narrative that they were able to "borrow" several more! This is clearly a typo and I would infer that the author meant to write "64 megabytes" and tacked on an extra zero, out of habit or hyperbole.
  - chadaustin 1y ago
    You are straight up wrong. The first computer I ever built was a Pentium 2, RivaTNT, and it had 640 MB RAM. I can’t find the purchase receipts or specific board brand but it had four SDRAM slots, and I had it populated with 2x64 and 2x256. Edit: Found it in some old files of mine: I was wrong! Not four DIMM slots... three! One must have been 128 and the other two 256. Pentium II 400, 512k cache Abit BF6 motherboard 640 MB PC100 SDRAM 21" Sony CPD-G500 (19.8" viewable, .24 dot pitch) 17" ViewSonic monitor (16" viewable, .27 dot pitch) RivaTNT PCI video card with 16 MB VRAM Creative SB Live! Creative 5x DVD, 32x CD drive Sony CD-RW (2, 4, 24) 80 GB Western Digital ATA/100 40 GB Western Digital ATA/100 17.2 GB Maxtor UltraDMA/33 HDD 10.0 GB Maxtor UltraDMA/33 HDD Cambridge SoundWorks FourPointSurround FPS2000 Digital 3Com OfficeConnect 10/100 EtherNet card 3 Microsoft SideWinder Gamepads Labtec AM-252 Microphone Promise IDE Controller card Hauppage WinTV-Theatre Tuner Card
    - AStonesThrow 1y ago
      Alright then! Humbly, I stand corrected about my poor speculation without research. It looks like 640MiB has been a perfectly achievable configuration, especially with 2x256+2x64 or such. That is, I must say, a huge amount of RAM. Like, way more than any video game ever specified in HW requirements. What use cases applied that you could use up 640MiB in that era, I wouldn't know! I remain a bit mystified about why it would be a hard maximum, though. Did such motherboards prevent the user from installing 4x256MiB for a cool 1GiB of DRAM? Was the OS having trouble addressing or utilizing it all? 640MiB is not a mathematical sort of maximum I was familiar with from the late 1990s. 4GiB is obviously your upper limit, with a 32-bit address bus... and again, if 640MiB were installed, that's only 2 free bits on that bus. So I'm still a little curious about this number being dropped in the article. More info would be enlightening! And thank you for speaking up to correct me! No wonder it was down-voted!
      - chadaustin 1y ago
        I did a bunch of media and software development back then so RAM helped a lot. Why 640? Not sure. My particular board could have gone up to 768. I did some googling and found some boards that maxed out at 1 GB. That was a weird time in computing. Things were getting fast and big quickly (not that many years later, I built a dual-socket Xeon at 2.8 GHz, and before that my brother had a dual socket P3 at 700 MHz.) but all the expansion boards were so special-purpose. I remember going out of my way to pick a board with something like seven expansion slots. But I think your question about why the author said 640 is fair! Maybe they had a machine like mine around then. Or maybe it’s something NVIDIA was designing around?

rjsw 1y ago

Maybe that is what they were thinking but anything designed to work with a PCI bus would have been introduced after PCs became capable of using more memory than that.

usefulcat 1y ago

It's hard to tell exactly what time frame the author is referencing there. For context, NV1 was released in '95, by which time it was not uncommon for a new PC to have 8-16 MB of memory (I had a 486 with 16 MB by '94). Especially if you planned to use it for gaming.

npalli 1y ago

The sentence and paragraph which makes it clear that this was megabytes and not kilobytes At a time when PC memory maxed out at 640 megabytes, the fact that the PCI bus could address 4 gigabytes meant that quite a few of its address bits were surplus. So we decided to increase the amount of data shipped in each bus cycle by using some of them as data. IIRC NV1 used 23 address bits, occupying 1/512th of the total space. 7 of the 23 selected one of the 128 virtual FIFOs, allowing 128 different processes to share access to the hardware. We figured 128 processes was plenty.

AStonesThrow 1y ago
Okay but "640" is a completely fictitious number for installed RAM in any given PC. PC memory was nearly always sold in powers of two. So you could have SIMMs in capacity of 1MiB, 2MiB, 4, 8, 16MiB. You could usually mix-and-match these memory modules, and some PCs had 2 slots, some had 4, some had a different number of slots. So if you think about 4 slots that can hold some sort of maximum, we're thinking 64MiB is a very common maximum for a consumer PC, and that may be 2x32 or 4x16MiB. Lots of people ran up against that limit for sure. 640MiB is an absurd number if you think mathematically. How do you divide that up? If 4 SIMMs are installed, then their capacity is 160MiB each? No such hardware ever existed. IIRC, individual SIMMs were commonly maxed at 64MiB, and it was not physically possible to make a "monster memory module" larger than that. Furthermore, while 64MiB requires 26 bits to address, 640MiB requires 30 address bits on the bus. If a hypothetical PC had 640MiB in use by the OS, then only 2 pins would be unused on the address bus! That is clearly at odds with their narrative that they were able to "borrow" several more! This is clearly a typo and I would infer that the author meant to write "64 megabytes" and tacked on an extra zero, out of habit or hyperbole.
- chadaustin 1y ago
  You are straight up wrong. The first computer I ever built was a Pentium 2, RivaTNT, and it had 640 MB RAM. I can’t find the purchase receipts or specific board brand but it had four SDRAM slots, and I had it populated with 2x64 and 2x256. Edit: Found it in some old files of mine: I was wrong! Not four DIMM slots... three! One must have been 128 and the other two 256. Pentium II 400, 512k cache Abit BF6 motherboard 640 MB PC100 SDRAM 21" Sony CPD-G500 (19.8" viewable, .24 dot pitch) 17" ViewSonic monitor (16" viewable, .27 dot pitch) RivaTNT PCI video card with 16 MB VRAM Creative SB Live! Creative 5x DVD, 32x CD drive Sony CD-RW (2, 4, 24) 80 GB Western Digital ATA/100 40 GB Western Digital ATA/100 17.2 GB Maxtor UltraDMA/33 HDD 10.0 GB Maxtor UltraDMA/33 HDD Cambridge SoundWorks FourPointSurround FPS2000 Digital 3Com OfficeConnect 10/100 EtherNet card 3 Microsoft SideWinder Gamepads Labtec AM-252 Microphone Promise IDE Controller card Hauppage WinTV-Theatre Tuner Card
  - AStonesThrow 1y ago
    Alright then! Humbly, I stand corrected about my poor speculation without research. It looks like 640MiB has been a perfectly achievable configuration, especially with 2x256+2x64 or such. That is, I must say, a huge amount of RAM. Like, way more than any video game ever specified in HW requirements. What use cases applied that you could use up 640MiB in that era, I wouldn't know! I remain a bit mystified about why it would be a hard maximum, though. Did such motherboards prevent the user from installing 4x256MiB for a cool 1GiB of DRAM? Was the OS having trouble addressing or utilizing it all? 640MiB is not a mathematical sort of maximum I was familiar with from the late 1990s. 4GiB is obviously your upper limit, with a 32-bit address bus... and again, if 640MiB were installed, that's only 2 free bits on that bus. So I'm still a little curious about this number being dropped in the article. More info would be enlightening! And thank you for speaking up to correct me! No wonder it was down-voted!
    - chadaustin 1y ago
      I did a bunch of media and software development back then so RAM helped a lot. Why 640? Not sure. My particular board could have gone up to 768. I did some googling and found some boards that maxed out at 1 GB. That was a weird time in computing. Things were getting fast and big quickly (not that many years later, I built a dual-socket Xeon at 2.8 GHz, and before that my brother had a dual socket P3 at 700 MHz.) but all the expansion boards were so special-purpose. I remember going out of my way to pick a board with something like seven expansion slots. But I think your question about why the author said 640 is fair! Maybe they had a machine like mine around then. Or maybe it’s something NVIDIA was designing around?