Neo Geo CDZ Single or Double Speed: Let's Discuss

[NeoTurfMasta]

This has been debated a lot over the years. We all know SNK had some colorful marketing, "24Bit" right.

The CDZ was marketed in Japan as having a "Double Speed CD-ROM Drive." Were they lying? Let's look at the evidence.

I first took a look a this site with 'X' drive specs:
http://whatis.techtarget.com/definition/X-compact-disc-access-time

I know these are probably not 100% accurate, but I think its safe to say it's a good baseline. I would also think it's safe to say that a 1x speed cannot read a disc spinning at speeds in the high 2x ranges.

So let's start there, CD speed. I took an unmodified Top Loader and CDZ, marked a disc with some white tape and filmed in slow motion. Here are the results.

This video shows roughly how many rotations within a 1 second time frame.

The Top Loader spins at around 8-9 revolutions per second, or what would be around 480-540 RPM. Easily in the 1X chart above.

The CDZ spins between 17-18 RPS, or 1020-1080 RPM. So double the speed of the Top Loader and within the 2X range on the chart.

The same game was used, Puzzle Bobble, both during data load progress. I just picked those two time frames because the white marker was in a good position to easily read rotations.

OK, so we know the rotation speeds. I took it a bit further. I hooked up the Top Loader CD Drive to my CDZ and it worked. Guess what speed it ran? The same 1x rotation speeds as the Top Loader with no change at all.

Lets look at the chips. The Top Loader uses the LC8915 "CD-ROM host and error correction chip"

https://wiki.neogeodev.org/index.php?title=LC89515

The specs of that exact chip doesn't say anything about "Single Speed", however, its upgrade does. The LC89617:

The last line, "The improved version (of the Top Loader chip) additionally supports double speed operation". So I think it's safe to assume that the older Top Loader chip does not support 2x.

From there I put a CDZ drive in the Top Loader and it does just that, the drive slows down operation to the 1x speeds. That's pretty convincing to me that there are 2 different drive speeds.

When you load a game in a regular CDZ there are 2 speeds that you can see without a camera, high speed when reading data, then back down to low when playing the Redbook CD audio.

I know RPMs are not definitive results, what we need next is a way to measure the actual transfer rates.

 

[fenikso]

What are the chances it spins double speed, but doesn't get the higher transfer rate? What would even be the point of the (probably more expensive) double speed drive then?

 

[NeoTurfMasta]

What are the chances it spins double speed, but doesn't get the higher transfer rate? What would even be the point of the (probably more expensive) double speed drive then?

I'm assuming that the CDZ isn't getting the full benefit of the 2x speed, but there is some improvement.

The CDZ's loading improvements aren't solely connected to some "faster caching etc", because if it was, I'd think we would see some boost when hooking up the Top Loader drive to the CDZ. Again, the load times were identical to the Top Loader when I put a Top Loader CD Drive on the CDZ.

 

[Tarma]

Thanks for going to the effort of looking into this properly - as a big NGCD fan I certainly appreciate it

The CD-ROM on the CDZ is from Sharp, and is a different model to the one used in the earlier machines, but that could be just down to obsolescence, or cost reductions. Is there any way of running the part number for the CD-ROM past Sharp to confirm the spec? I've done searches online, but can only find links into parts suppliers with info that generally infers that this CD-ROM was also used in CD players of the time.

If the latter is true, why put a dual speed CD drive in a CD player? To keep costs down you'd just use a single speed drive, no?

I really don't know enough about the CD format... : /

 

[BlackaneseNiNjA]

I'm assuming that the CDZ isn't getting the full benefit of the 2x speed, but there is some improvement.

The CDZ's loading improvements aren't solely connected to some "faster caching etc", because if it was, I'd think we would see some boost when hooking up the Top Loader drive to the CDZ. Again, the load times were identical to the Top Loader when I put a Top Loader CD Drive on the CDZ.

Great tests and an awesome observation. I know the CDZ drive speed has been contested over the years, but this finally sheds more light on the CDZ's loading speed solution. Thank you as always NTM!

 

[Fakk2]

I did tests between the Neo-Geo CD US top loader and the JPN CDZ back in the day (1995-1996), and not only is the CDZ a double speed drive, but for games made AFTER the CDZ came out, most of them are written in a way that allows the CDZ to take more advantage to the extra Cache of the games for faster loading in between screens like the options screen, and even faster re-loading of stages already loaded after you die and have to restart the stage. Games that use this technique are like the Aero Fighters series. Sadly, this is not the most noticeable on the bigger games like the later KOF's, Real Bouts, and Metal Slugs, etc... but for the smaller games that are 106megs and under, this is very noticeable. I was simply using a stop watch back then, and everything loaded 2x as fast on the CDZ than on the regular NeoCD, but as stated the bigger games loaded a bit slower the first time around for each stage than it should on a 2x cd rom drive, and i think that is due to loading certain portions of that data into the ram of the system. This is just my opinion though.

Also worth noting, the CDZ seems to have slightly better s-video picture quality, but slightly worse analogue audio output, and vise versa. Not sure why this is, but I was very disappointed in the CDZ's audio output.

 

[awbacon]

That's a mighty impressive experiment NeoTurfMasta!

 

[Katsu]

Always wondered this myself. Thanks for putting in the actual work on this!

P.S. I was a little surprised that the tape didn't cause an imbalance. Not saying that it would affect drive rotation as much as possibly damage the drive. I have no proof of this, I just remember back in the day people slapping on labels on one side of game CDs at some mom and pop rental stores and people freaking out about it damaging their CD drive. I always hated rental labels on discs.

 

[NeoTurfMasta]

I also asked Furrtek to help with this after I posted the videos. He read the transfer rate through the drive's serial data line. With some calculations, he did confirm that the FL and TL systems are transferring at single speed rates, while the CDZ is double.

We really need to put these findings on the dev Wiki.

 

[NeoSneth]

So would it be possible to run the 1x at 2x speed?
I find this all highly informative and entertaining.

 

[NeoTurfMasta]

So would it be possible to run the 1x at 2x speed?
I find this all highly informative and entertaining.

You know, that's a good question. I wonder if swapping the CD-ROM host chip and putting a 2x drive in a toploader is possible. I'll look into it.

 

[GohanX]

You know, that's a good question. I wonder if swapping the CD-ROM host chip and putting a 2x drive in a front loader is possible. I'll look into it.

Fixed that for ya.

 

[famicommander]

If someone makes a way for my toploader to be as fast as a CDZ I'll give them all the monies. all of them.

 

[GohanX]

But you only got bout tree-fiddy.

 

[famicommander]

But you only got bout tree-fiddy.

Not just all of my monies.

ALL of them. I'll be robbing old ladies and taking amiga1200's lunch money and sending it to the person who accomplishes this task.

 

[Lach]

2x? just install a blu-ray drive host chip in the pcb with a laser booster and we're there man, easy.

 

[madman]

2x? just install a blu-ray drive host chip in the pcb with a laser booster and we're there man, easy.

A 2x front loader would be teh tits, even if it did work, is it possible to source the CD controller chips or one that's pin compatible?

 

[NeoTurfMasta]

A 2x front loader would be teh tits, even if it did work, is it possible to source the CD controller chips or one that's pin compatible?

Finding parts will definitely be an issue. The upgraded chip I mention in the first post is not pin compatible, so an adapter would have to be made. Honestly, the amount of work involved to do this doesn't seem very worth it. Probably better to make an ODE with modern parts, but that's beyond my skill set.

 

[madman]

Yeah, there's probably only a handful of people in the world who would care, but it's cool either way.

 

[Neo Alec]

I always assumed the CDZ was 2X back in the day. SNK's marketing said as much and we had no reason to doubt it. Plus the drive has the type of spindle where you have to press the disc down into place, usually indicating a double speed drive back in the day.

Who started the rumor that it isn't 2X? Know-it-alls used to bust into our threads and take the wind out of our sails.

 

[madman]

I always assumed the CDZ was 2X back in the day. SNK's marketing said as much and we had no reason to doubt it. Plus the drive has the type of spindle where you have to press the disc down into place, usually indicating a double speed drive back in the day.

What other top loading 2x CD-ROMs were you using "back in the day?" My 2x computer CD-ROM used a tray, there was no spindle to press down.

 

[Neo Alec]

What other top loading 2x CD-ROMs were you using "back in the day?" My 2x computer CD-ROM used a tray, there was no spindle to press down.

Saturn, PSX 3DO. Jaguar CD had a 2X drive, but no one I knew had one. CD-I was 1X; it was older hardware, but made up for it pretty well with the MPEG expansion card.

 

[NeoTurfMasta]

Saturn, PSX 3DO. Jaguar CD had a 2X drive, but no one I knew had one. CD-I was 1X; it was older hardware, but made up for it pretty well with the MPEG expansion card.

The Goldstar 3DO actually has the upgraded Top Loader chip. So far, that's the only place I have been able to find one.

 

[madman]

Saturn, PSX 3DO. Jaguar CD had a 2X drive, but no one I knew had one. CD-I was 1X; it was older hardware, but made up for it pretty well with the MPEG expansion card.

I guess the question was more about the spindle you have to press down on. Jag CD doesn't have that, there's a clamp type thing in the top half. I don't recall having to press down on the other spindles, but I haven't touched my PSX in years. Irrelevant I suppose, I just don't recall that being a sign of a 2x drive and don't recall any similar to the CDZ with an actual locking mechanism you press down.

 

[Neo Alec]

I guess the question was more about the spindle you have to press down on. Jag CD doesn't have that, there's a clamp type thing in the top half. I don't recall having to press down on the other spindles, but I haven't touched my PSX in years. Irrelevant I suppose, I just don't recall that being a sign of a 2x drive and don't recall any similar to the CDZ with an actual locking mechanism you press down.

It would be more accurate to say the disc must be snapped into place. Anyway, 2x top loading drives never seemed to have the 1X style ones where the disc simply sits loosely in place before you close the lid. The snap-in style of the CDZ was one giveaway for me from the beginning.