Talk:Bull Gamma 60

error in figures?

The article says this about the magnetic tape " (300 bits / inch), with a 750m or 110m length, allowing a capacity of 7 MB or 11 MB." 300 bits per inch is 11,811 bits per meter, so 750m would be 8.8 million bits or 1.1 million bytes. 110m (I suspect it was 1100m) would be 1.3 million bits, or 162,400 bytes. Bubba73 ^{You talkin' to me?} 19:34, 14 August 2023 (UTC)

Well, it probably means 300 bits per inch for each track on the tape. But I think the second length should be 1100 meters, because 3600 feet was a common length for reels of tape, and that is 1097 meters. 750 meters is 2460 feet, and 2400 was another common length of reels of tape. Bubba73 ^{You talkin' to me?} 21:32, 14 August 2023 (UTC)

Thank you for spotting this. Yes, 110m instead of 1100m is indeed a typo.

I noticed some discrepancies in the various documentation I could find for the Gamma 60. Some sources mentioned a 730m tape length while others mentioned 750m (I believe it's 730m as that's precisely 2400 feet). Some also mentioned 200 bits per inch, while others mentioned 300 bits per inch or 30 words per centimeter. However, that doesn't add up since 30 w/cm would equate to 30 words * 24 bits * 2.54cm = 1828 bits per inch. 3 words per cm would work though, as that would be equate to about 200 bits / inch.

When I did the math, I assumed there were 30 words stored per centimeter and a 730-meter tape. Thus, we have 30 * 100 * 730 = 2,190,000 24-bit words (equivalent to 6,750,000 bytes or 6.5 MB) and 9.4 MB for 1100m. This appeared to match reasonably closely with what I read in the documentation, which mentioned a range of "7,000,000 to 11,000,000 digits." However, I couldn't determine whether those "digits" were in binary or BCD (48-bit). Someone also mentioned there were words (24-bit).

Let's do the math from a different perspective. The fairly similar Univac I tapes, with a 1200 feet length and a density of 128 bytes per inch, had a capacity of 1.5 MB. The G60 tapes should have 1.56 times the density and twice the length, hence a 1.5 * 1.56 * 2 = 4.68 MB capacity, or 1.5 * 1.56 * 3 = 7 MB for 1100m. That again sounds reasonable.

Based on these calculations, I think the capacity was likely somewhere around 5 MB. However, since I can't find reliable data, I will omit the details for now. Please feel free to share your thoughts on this.

Damien.b (talk) 23:32, 14 August 2023 (UTC)

In my experience with reel-to-reel audio tape in the US, I used 1200-foot, 1800-foot, and 2400-foot reels. Based on the speed they were running, they were a little longer than the stated length. I remember that I had one tape that was marked 2475 feet, which is close to 750 meters. Bubba73 ^{You talkin' to me?} 00:48, 16 August 2023 (UTC)