10 Nov 2017 - Why I use BCD for scorekeeping in 8088 games
For a while I’ve gotten a LOT of questions about why the C64 version, and my upcoming ASM version of Paku Paku tracks scores in BCD – Binary Coded Decimal. The simple fact is that it is WAY faster even with the overhead of the long score additions. Sure, each score takes 8 bytes (I display a fake ‘0’ after since all score values are multiples of ten, 9 digits is overkill) instead of four...
But the simple fact is that whilst yes, adding a value to the score takes eight additions with AAA (ascii adjust for addition), that is still WAY faster than the multiple divides (16 in total) needed to turn a 32 bit integer into ASCII or even just BCD -- and you'd need it in one or the other to output to the screen! You basically NEED unpacked (aka 8 bits per digit) binary coded decimal or something like it to handle display numeric output in a way Joe Sixpack and Susie Sunshine can digest. "normal people" aren't going to be happy if you display your scores in a game in hexadecimal!
10 Nov 2017 - Why I use BCD for scorekeeping in 8088 games
For a while I’ve gotten a LOT of questions about why the C64 version, and my upcoming ASM version of Paku Paku tracks scores in BCD – Binary Coded Decimal. The simple fact is that it is WAY faster even with the overhead of the long score additions. Sure, each score takes 8 bytes (I display a fake ‘0’ after since all score values are multiples of ten, 9 digits is overkill) instead of four...
But the simple fact is that whilst yes, adding a value to the score takes eight additions with AAA (ascii adjust for addition), that is still WAY faster than the multiple divides (16 in total) needed to turn a 32 bit integer into ASCII or even just BCD -- and you'd need it in one or the other to output to the screen! You basically NEED unpacked (aka 8 bits per digit) binary coded decimal or something like it to handle display numeric output in a way Joe Sixpack and Susie Sunshine can digest. "normal people" aren't going to be happy if you display your scores in a game in hexadecimal!
10 Nov 2017 - Why I use BCD for scorekeeping in 8088 games
For a while I’ve gotten a LOT of questions about why the C64 version, and my upcoming ASM version of Paku Paku tracks scores in BCD – Binary Coded Decimal. The simple fact is that it is WAY faster even with the overhead of the long score additions. Sure, each score takes 8 bytes (I display a fake ‘0’ after since all score values are multiples of ten, 9 digits is overkill) instead of four...
But the simple fact is that whilst yes, adding a value to the score takes eight additions with AAA (ascii adjust for addition), that is still WAY faster than the multiple divides (16 in total) needed to turn a 32 bit integer into ASCII or even just BCD -- and you'd need it in one or the other to output to the screen! You basically NEED unpacked (aka 8 bits per digit) binary coded decimal or something like it to handle display numeric output in a way Joe Sixpack and Susie Sunshine can digest. "normal people" aren't going to be happy if you display your scores in a game in hexadecimal!
