Blank GBA carts: Why not measure in MB?

[crashwg]

After being mislead for the past couple weeks, I have just found out that GBA blank carts are measured in "M" and not "MB" therefore a 512m card can not hold my entire collection of NES roms and thensome as I had originally thought.

In fact you can only fit 16 of the smallest GBA games, zipped, on a 512m cart!  

An easy way I have found to find out how many games you can fit on a cart is this:  Multiply the size, in MB, by 16 and that gives you the size in "M".

Why do they have to make things so dificult?  I know it is posibly to fit 512MB in a memory card/stick/whatever... why can't they do that with GBA carts?

[AmericanDemon]

Then each game would run oh about $150.00.  Thats some mighty expensive carts you got to be askin for.....

[darktemp]

You multiply by 8 not 16.  Carts have always been in megabits or kilobits, maybe it's a japanese thing?

[AlanS17]

You multiply by 8 not 16.  Carts have always been in megabits or kilobits, maybe it's a japanese thing?

I figure it's because the first games were so small that if you were measuring in MB you would be spitting out fractions... and then the convention just stuck.

[crashwg]

You multiply by 8 not 16.  Carts have always been in megabits or kilobits, maybe it's a japanese thing?

Hmmm... From a response from one of the top sellers of blank carts:

PC MB (Bytes) | Zipped on PC  |M (Bits) on GBA
4 MB                 ~2MB                     = 32M
8 MB                 ~4MB                     = 64M
16 MB               ~8MB                     = 128M
32 MB               ~16MB                   = 256M
64 MB               ~32MB                   = 512M

According to that table, you would be correct... before the zipping process that is.  My calculations are of the files, the way they will be put on the cart.

[b3atmania]

After being mislead for the past couple weeks, I have just found out that GBA blank carts are measured in "M" and not "MB" therefore a 512m card can not hold my entire collection of NES roms and thensome as I had originally thought.

In fact you can only fit 16 of the smallest GBA games, zipped, on a 512m cart!

Consumers tend to measure storage capacity in bytes. Electrical engineers measure storage in bits. Why you ask? Well, there are various ways to implement memory using different memory parts.

Say you want to wire 32kilobyte ROM to a Z80 which has an 8-bit databus. You could use a 32k x 8 bit ROM chip. Or use two 32k x 4 bit ROM chips. See, the total amount of bits is what matters. In the end it won't matter as you can easily translate between them (n bit = n/8 bytes), you just have know if you are talking bits or bytes.

Why do they have to make things so dificult?  I know it is posibly to fit 512MB in a memory card/stick/whatever... why can't they do that with GBA carts?

Memory sticks/cards are block devices. They read and store data in blocks. This is cheap memory technology and is suitable to map a file system on. However, this type of memory is not suited to the GBA as the GBA need fast random access to single bytes in memory. Fast random access flash memory is far more expensive than the type you find in common memory sticks/cards.

[abrannan]

You multiply by 8 not 16.  Carts have always been in megabits or kilobits, maybe it's a japanese thing?

Hmmm... From a response from one of the top sellers of blank carts:

PC MB (Bytes) | Zipped on PC  |M (Bits) on GBA
4 MB                 ~2MB                     = 32M
8 MB                 ~4MB                     = 64M
16 MB               ~8MB                     = 128M
32 MB               ~16MB                   = 256M
64 MB               ~32MB                   = 512M

According to that table, you would be correct... before the zipping process that is.  My calculations are of the files, the way they will be put on the cart.

You never count zipping, because zipping is variable based upon the randomness of the data in the file to be zipped.  Truly random data can actually end up being larger when zipped, because of the header information that zipping adds.  Whereas with text data that isn't very random at all you can achieve a file thats <1/4th the size of the original.